Journal articles on the topic 'Digested sludges'
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1
Hardegen, Justus, Patrick Braeutigam, Christian Abendroth, and Thomas Wichard. "Bisphenol A: Quantification in Complex Matrices and Removal by Anaerobic Sludges." Pollutants 1, no. 4 (October 14, 2021): 194–206. http://dx.doi.org/10.3390/pollutants1040016.
Abstract:
The endocrine disruptor bisphenol A (BPA) is one of the most commonly found micropollutants in the environment. However, the biodegradation of BPA under anaerobic (methanogenic) conditions is still an understudied process in wastewater treatment systems. The current study thus addresses the need for a simple and user-friendly analytical method for the rapid and accurate quantification of BPA in complex matrices such as digested and co-digester sludges. We established a microwave-assisted extraction method, followed by derivatization and gas chromatography–mass spectrometry to quantify BPA by comparing it with a deuterated internal standard. The BPA removal capabilities of three digester sludges and three co-digester sludges were examined under mesophilic methanogenic conditions in biogas plants. The endogenous BPA concentration (dry weight) ranged from 1596 to 10,973 µg kg−1 in digested sewage sludges, and from below the limit of quantification to 9069 µg kg−1 in co-digester sludges. When BPA was added to the sludges, the removal capabilities ranged from not significant to 50% after 21 days of incubation. Biogas production was unaffected by the addition of BPA (228 µg kg−1) to the aqueous sludge. The study demonstrated that BPA could be removed under anaerobic conditions in accustomed inoculates. The findings have far-reaching implications for understanding BPA persistence and detoxification under anaerobic conditions.
2
Martel, C. James, and Carl J. Diener. "Pilot-scale studies of sludge dewatering in a freezing bed." Canadian Journal of Civil Engineering 18, no. 4 (August 1, 1991): 681–89. http://dx.doi.org/10.1139/l91-083.
Abstract:
In 1986, a pilot-scale sludge freezing bed was constructed at the U.S. Army Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire, U.S.A. This bed was operated for the next three years using both anaerobically and aerobically digested sludges. Results indicate that both sludges were effectively dewatered by this process. The maximum depth of sludge frozen during this study was 1.14 m. The final solid contents were 39.3% and 24.5% for anaerobically digested and aerobically digested sludges respectively. The quality of the meltwater from the bed was similar to raw wastewater. The actual depth of sludge frozen and thawed in the bed during each year of operation was very close to that predicted by design models. Operational experience demonstrated the importance of a sand layer at the bottom of the bed for adequate drainage. Also, odors developed when the meltwater was allowed to accumulate in the bed. Odors were not a problem when the meltwater was drained away as quickly as it formed. Both sludges were easily removed with a front-end loader. Key words: sludge freezing bed, freeze–thaw conditioning, freeze–thaw separation, sludge dewatering, freezing bed.
3
Noyola, Adalberto, and Gloria Moreno. "Granule production from raw waste activated sludge." Water Science and Technology 30, no. 12 (December 1, 1994): 339–46. http://dx.doi.org/10.2166/wst.1994.0633.
Abstract:
Granulation is an important characteristic of sludges used in upflow anaerobic sludge blanket (UASB) reactors. As the UASB technology is rapidly spreading, there is a need of granular sludge for inoculation of new reactors, particularly in those countries where anaerobic technologies have been just recently accepted. Alternative sources of inocula are digested sludge, digested manure, septic tank sludges and pond sediments. Raw waste activated sludges have also been identified as a convenient material for reactor seeding, with previous treatment. In this work, anaerobic flocculant sludge obtained from raw waste activated sludge has been granulated with hydraulic stress, in a lab-scale column under different upflow velocities (1 to 50 m h−1). A methodology is proposed for enhancing the quality of non granular anaerobic sludges in batch treatments of less than 8 hours. The granular sludge produced was used as inoculum for a UASB lab scale reactor. The seed sludge improved all its characteristics and maintained the granulation, in spite of the low velocity (0.08 m h−1) applied.
4
Cheng, H. F., S. Y. Chen, and J. G. Lin. "Hazardous organic matters in municipal sewage sludge in Taiwan." Water Science and Technology 44, no. 10 (November 1, 2001): 65–70. http://dx.doi.org/10.2166/wst.2001.0582.
Abstract:
Application of municipal sewage sludge to agricultural land has attracted significant attention in recent years because it conserves abundant nutrients and hydrocarbons that can be used as a soil amendment. The presence of hazardous organic matters (HOMs) in sewage sludge limits the feasibility of reuse of sewage sludge. The purpose of this study was to investigate the types and the concentrations of HOMs in municipal sewage sludge in Taiwan. An efficient SFE/GC/MS method was used to determine HOMs in sludge samples. The results indicated that di-(2-ethylhexyl) phthalate (DEHP) was persistently found in both aerobically and anaerobically digested sludges. 4-nonylphenol (4-NP) was only found in anaerobically digested sludges. Both DEHP and 4-NP have been characterized as endocrine disrupting chemicals (EDCs) or environmental endorine disruptors (EEDs). It suggested that sludges containing high levels of DEHP and 4-NP need further treatment and reduction of possible impacts on the environment before their reuse as soil fertilizers.
5
Bux, F., B. Atkinson, and H. C. Kasan. "Zinc biosorption by waste activated and digested sludges." Water Science and Technology 39, no. 10-11 (May 1, 1999): 127–30. http://dx.doi.org/10.2166/wst.1999.0640.
Abstract:
Biological matter is known for its ability to biosorb solubilised heavy metal ions to its surface. Experiments were therefore conducted to assess the biosorptive capacity of two waste products of the wastewater treatment industry ie., waste activated and waste digested sludge. Surface charge of each was determined in order to relate electronegativity with biosorptive potential. Activated sludge was found to be more effective than digested sludge for removal of zinc from a metal plating effluent, viz., 5.9 mg Zn/(g sludge)−1 as opposed to 4.0 mg/g, respectively, as well as producing a higher net negative charge. It was also noted that as initial zinc concentrations in solution increased there was a concomitant increase in sludge biosorption capacity. Activated and digested sludges were capable of biosorbing zinc from a metal plating effluent although activated sludge showed better potential for industrial application.
6
Shang, Y., B. R. Johnson, and R. Sieger. "Application of the IWA Anaerobic Digestion Model (ADM1) for simulating full-scale anaerobic sewage sludge digestion." Water Science and Technology 52, no. 1-2 (July 1, 2005): 487–92. http://dx.doi.org/10.2166/wst.2005.0557.
Abstract:
A steady-state implementation of the IWA Anaerobic Digestion Model No. 1 (ADM1) has been applied to the anaerobic digesters in two wastewater treatment plants. The two plants have a wastewater treatment capacity of 76,000 and 820,000 m3/day, respectively, with approximately 12 and 205 dry metric tons sludge fed to digesters per day. The main purpose of this study is to compare the ADM1 model results with full-scale anaerobic digestion performance. For both plants, the prediction of the steady-state ADM1 implementation using the suggested physico-chemical and biochemical parameter values was able to reflect the results from the actual digester operations to a reasonable degree of accuracy on all parameters. The predicted total solids (TS) and volatile solids (VS) concentration in the digested biosolids, as well as the digester volatile solids destruction (VSD), biogas production and biogas yield are within 10% of the actual digester data. This study demonstrated that the ADM1 is a powerful tool for predicting the steady-state behaviour of anaerobic digesters treating sewage sludges. In addition, it showed that the use of a whole wastewater treatment plant simulator for fractionating the digester influent into the ADM1 input parameters was successful.
7
Watanabe, Haruki, Tomokazu Kitamura, Shuichi Ochi, and Masaaki Ozaki. "Inactivation of pathogenic bacteria under mesophilic and thermophilic conditions." Water Science and Technology 36, no. 6-7 (September 1, 1997): 25–32. http://dx.doi.org/10.2166/wst.1997.0571.
Abstract:
This paper concerns field survey and laboratory experiment on the inactivation of pathogenic bacteria during sludge treatment processes with particular emphasis on anaerobic digestion process. We surveyed the inactivation of pathogenic bacteria processes by sampling various types of sludges from 17 wastewater treatment plants located in Japan and counting the number of bacteria in the sampled sludges. The bacteria we counted included fecal coliform groups, enterococcus and salmonella. The median number of fecal coliform groups in primary sludge was found to be 105 MPN/g, while the number of fecal coliform groups in digested sludge decreased to 103 MPN/g. We also confirmed that the treatments of dewatering using inorganic coagulant, drying and composting are also effective in inactivating pathogenic bacteria. In addition, we studied the performance conditions of anaerobic digestion and the degree of inactivation of pathogenic bacteria in the experiment of anaerobic treatment of the primary sludge. This study showed that the number of fecal coliform groups in mesophilic digestion sludge was in the range of 102 to 104 MPN/g regardless of the HRT, whereas the number of bacteria in thermophilic digestion sludge was of the order of 100 MPN/g, clearly indicating that the number of bacteria substantially decreases when the sludge is digested at thermophilic temperature. The number of enterococcus in digested sludge was in the range of 102 to 105 MPN/g after the sludge was subjected to mesophilic digestion while the number decreased to 100 MPN/g after the sludge was digested at thermophilic temperature. The number of salmonella in digested sludge was in the range of 1.8 to 30 MPN/4g after the sludge was digested at mesophilic temperature, but the number decreased to less than 1.8 MPN/4g after the sludge went through thermophilic digestion process. The thermophilic digestion is thus effective in inactivating pathogenic bacteria.
8
Scheminski, A., R. Krull, and D. C. Hempel. "Oxidative treatment of digested sewage sludge with ozone." Water Science and Technology 42, no. 9 (November 1, 2000): 151–58. http://dx.doi.org/10.2166/wst.2000.0193.
Abstract:
A process to improve anaerobic biodegradation of wastewater treatment sludges is investigated. Recalcitrant organic compounds which are contained in biologically stabilized digested sludge become biodegradable by partial oxidation using ozone and ozone in combination with hydrogen peroxide respectively. By oxidation with ozone, cell walls of microorganisms were destroyed and cytoplasm dissolved in sludge water. Water insoluble substances with high molecular weight were split into smaller, water soluble and biodegradable fragments. Sludge matrix composition regarding protein, lipid and polysaccharide content changed. After ozone consumption of 0.2 gram ozone per gram organic dry matter, the degree of biodegradation of organic matter during the following anaerobic treatment increased to 42%. Due to the oxidizing pretreatment, the dewatering results of the sludges after biological decomposition deteriorated. The polymer demand to reach isoelectric point increased with ozone consumption. Compared to mechanical, thermal and thermochemical disintegration, partial oxidation by ozone achieved highest degrees of organic matter decomposition in the following anaerobic biodegradation.
9
Sarikaya, Hasan Z., and Salah Al-Marshoud. "Improvement of Dewatering Characteristics of Aerobically Digested Sludges." Water Science and Technology 28, no. 1 (July 1, 1993): 47–51. http://dx.doi.org/10.2166/wst.1993.0013.
Abstract:
The aim of this study was to evaluate the influence of both sludge characteristics and operational parameters on polymer selection and optimal dose requirements to improve the dewatering characteristics of aerobically digested sludges of a contact stabilization activated sludge plant in Jeddah, Saudi Arabia. In order to determine the dewatering characteristics of the sludge samples, capillary suction time (CST) and specific resistance to filtration (SRF) were measured. Cationic conditioning polymers were found more effective than the anionic types. The optimum polymer dose was equal to 4.2 kg of polymer/ton of dry matter for three of the cationic polymers used in this study namely Zeetag 57, Superfloc C420, and Zeetag 92. The optimum dose requirements are increased substantially with increasing pH values. A linear relationship was found between the optimal polymer dose in mg/l and the sludge solids concentration. The optimum total mixing time was found to be 2 min: 30 sec of rapid mixing at 100 rpm and 90 sec of slow mixing at 40 rpm. The sludge temperature variations were found to have a slight effect on polymer dose requirements. A linear relationship was obtained between the CST and SRF with a correlation coefficient of 0.99.
10
Novak, J. T., N. Verma, and C. D. Muller. "The role of iron and aluminium in digestion and odor formation." Water Science and Technology 56, no. 9 (November 1, 2007): 59–65. http://dx.doi.org/10.2166/wst.2007.705.
Abstract:
The role of iron and aluminium in determining volatile solids reduction and odors from anaerobically digested, dewatered sludge cakes was evaluated from data collected from a variety of wastewater treatment plants. It was found that volatile solids reduction generally increased as the iron content of the sludge increased. It was also observed that odors increased with increasing iron. No correlation with aluminium or divalent cations was found. Based on these data it appears that the volatile solids reduction by anaerobic digestion is not useful for predicting the odors from anaerobically digested sludges.
11
De Leén, C., and D. Jenkins. "Removal of fecal coliforms by thermophilic anaerobic digestion processes." Water Science and Technology 46, no. 10 (November 1, 2002): 147–52. http://dx.doi.org/10.2166/wst.2002.0314.
Abstract:
Recent U.S. EPA regulations (40 CFR Section 503) specify maximum concentrations of pathogens and metals for Class A wastewater treatment plant sludges. The most common sludge process is mesophilic (35¡C) digestion which stabilizes the solids, produces a combustible gas but does not create an effluent that meets the 503 Class A pathogen requirements. This investigation was conducted to determine whether anaerobic digestion processes incorporating a thermophilic stage could achieve 503 Class A pathogen levels. The research reported here was a bench-scale screening study meant to identify the most promising process alternatives for further investigation. Fecal Coliform (FC) concentrations were used to assess disinfection efficiency. Digesters were 30 L capacity fed semi-continuously in draw-fill mode. Digester startup was rapid to produce true thermophiles. Temperature staging and pH were assessed in 3 sets of experiments: Set 1 were one stage (“acid phase”), Set 2 were one stage (“acid + methane phases”) and Set 3 were two stage (“acid phase” then “methanogenic phase”). Feed was a 1:1 mixture of Thickened Waste Activated Sludge and Primary Sludge. The following anaerobic digestion configurations and operating parameters allowed the production of digested sludge with a mean FC concentration statistically less than 103 (the regulatory value for Class A sludge): thermophilic single stage acid phase at 52 and 62°C; thermophilic single stage acid + methane phase at 48°C, 52°C and 62°C; two-stage mesophilic acid phase followed by mesophilic methane phase; two stage mesophilic acid phase followed by thermophilic methane phase at 48°C, 52°C and 62°C. If the maximum digested FC concentration must be below 103 MPN/g TS then the following digester configurations and operating conditions will be compliant: two stage mesophilic acid phase followed by thermophilic methane phase at 52°C and 62°C.
12
Wang, Jin, Zhen Jia Zhang, and Li Na Chi. "Character and Model of Anaerobic Granular Sludge Formation in the Sanitary Landfill." Advanced Materials Research 455-456 (January 2012): 1297–302. http://dx.doi.org/10.4028/www.scientific.net/amr.455-456.1297.
Abstract:
The microbiological structure characteristic and the particle diameter distribution of different sludges (aerobic excess sludge, sludge from sanitary landfill digested for one year, and granular sludge of pilot-scale expanded granular sludge bed (EGSB) reactor after 400 d of operation) were analyzed through scanning electron microscopy (SEM), transmission electron microscopy (TEM) and sieve. SEM of granules showed that the microbiological structure of the sludge from different sources had differences. But TEM proved that granules of EGSB and landfill both had similar kind of bacterial species i.e. Methanosarcina bacteri sp. There were obvious differences in the transformation trend of size distribution between different granular sludges. Three-step Model for the anaerobic granular sludge formation in sanitary landfill was put forward.
13
Park, Nathan D., Ronald W. Thring, and Steve S. Helle. "Comparison of methane production by co-digesting fruit and vegetable waste with first stage and second stage anaerobic digester sludge from a two stage digester." Water Science and Technology 65, no. 7 (April 1, 2012): 1252–57. http://dx.doi.org/10.2166/wst.2012.004.
Abstract:
Fruit and vegetable waste (FVW) was co-digested with first stage (FSS) and second stage anaerobic digester sludge (SSS) separately, over the course of 10 days, in batch reactors. Addition of FVW significantly increased the methane production in both sludges. After 10 days of digestion FSS + FVW produced 514 ± 57 L CH4 kg VS−1added compared with 392 ± 16 L CH4 for the SSS + FVW. The increased methane yield was most likely due to the higher inoculum substrate ratio of the FSS. The final VS and COD contents of the sewer sludge and FVW mixtures were not significantly different from the control values suggesting that all of the FVW added was degraded within 10 days. It is recommended that FVW be added to the first stage of the anaerobic digester in order to maximize methane generation.
14
Chu, C. W., C. S. Poon, and R. Y. H. Cheung. "Characterization of raw sludge, chemically modified sludge and anaerobically digested sludge in Hong Kong." Water Science and Technology 38, no. 2 (July 1, 1998): 25–32. http://dx.doi.org/10.2166/wst.1998.0095.
Abstract:
Chemically Enhanced Primary Treatment (CEPT) or Chemically Assisted Primary Sedimentation (CAPS) is being employed at the new sewage work on Stonecutters Island as part of the Strategic Sewage Disposal Scheme (SSDS) in Hong Kong. CAPS involves the use of chemical coagulants (such as lime or ferric chloride) to induce coagulation or flocculation and let these finely-divided particles form large aggregates (floc) so that they can settle out within a reasonable period of time. In this study, five sludge samples collected from different sewage treatment plants in Hong Kong were physically and chemically characterized. They were chemically modified sludge from Stonecutters Island (CAPS) raw sludge from Tai Po and Yuen Long Sewage Treatment Plant (STP) (rTP & rYL) and anaerobically digested sludge from Tai Po and Yuen Long STP (dTP & dYL). It was found that CAPS sludge was better than other 4 sludge samples in terms of settleability and dewaterability. CAPS sludge contained significant higher amounts (p<0.01) of extractable compounds than other sludges (except NO3− for dTP, NH4+ and PO43− for dYL). The concentration of total N and P in CAPS sludge were significantly higher (p<0.01) than other sludges (except dYL). The concentrations of total Cu, Pb, Ni, Cd, Cr and K in the CAPS sludge were also significantly higher (p<0.01) than other sludge samples. Most of the metals (Cr, Pb, Cr and Zn) in CAPS sludge were associated with the organically-bounded phase. It is concluded that there are significant differences in both physical and chemical properties between the chemically modified sludge and biological treated sludges.
15
Ravishankar, B. R., J. C. Auclair, and R. D. Tyagi. "Partitioning of Heavy Metals in Some Quebec Municipal Sludges." Water Quality Research Journal 29, no. 4 (November 1, 1994): 457–70. http://dx.doi.org/10.2166/wqrj.1994.029.
Abstract:
Abstract The process efficiency of metal bioleaching from sewage sludges depends upon various physicochemical characteristics of sludges and the forms in which metals are present in these sludge solids. The aim of this research work was to evaluate the metal speciation in some Quebec sludges with the help of a sequential extraction procedure, in order to better predict the bioleaching process. The distribution of Al, Cu, Fe, Mn and Zn in exchangeable, sorbed, organically bound, carbonate, and residual forms were compared among both undigested and digested sludges. Metal redistribution after aerobic sludge stabilization was also studied. Results indicate that the organic and residual fractions were the principal metal binding phases. Copper was present mostly in the residual fraction while the other metals were mostly organically bound. Statistical tests showed that metal speciation varied significantly from one sludge to another. In terms of metal distribution pattern observed, these sludges could not be regrouped according to the sludge type, their total solids concentration or their total metal concentration. However, the variation in metal distribution among Quebec sludges was similar to the variation range found in the U.K. and U.S. sludges. The metals showed a tendency to redistribute and move towards the organic fraction in stabilized sludges. In conclusion, the present study shows that sewage sludges of different origins do not have similar metal distribution and hence, the speciation of metals must be considered for each sludge on an individual basis in order to predict their fate during the bioleaching process.
16
Seghezzo, L., C. M. Cuevas, A. P. Trupiano, R. G. Guerra, S. M. González, G. Zeeman, and G. Lettinga. "Stability and activity of anaerobic sludge from UASB reactors treating sewage in subtropical regions." Water Science and Technology 54, no. 2 (July 1, 2006): 223–29. http://dx.doi.org/10.2166/wst.2006.509.
Abstract:
The production of small amounts of well-stabilized biological sludge is one of the main advantages of upflow anaerobic sludge bed (UASB) reactors over aerobic wastewater treatment systems. In this work, sludge produced in three pilot-scale UASB reactors used to treat sewage under subtropical conditions was assessed for both stability and specific methanogenic activity. Stability of primary sludge from settling tanks and digested sludge from conventional sludge digesters was also measured for comparison purposes. Kinetic parameters like the hydrolysis rate constant and the decay rate constant were calculated. High stability was observed in sludge from UASB reactors. Methanogenic activity in anaerobic sludges was relatively low, probably due to the low organic matter concentration in influent sewage. Knowledge on sludge growth rate, stability, and activity might be very useful to optimize sludge management activities in full-scale UASB reactors.
17
Prodanović, Jelena, Marina Šćiban, and Mirjana Antov. "Improvement of wastewater treatment by use of natural coagulants." Journal of Economic Development, Environment and People 2, no. 2 (June 22, 2013): 22. http://dx.doi.org/10.26458/jedep.v2i2.20.
Abstract:
An activated sludge and other organic sludges from wastewater treatment processes are usually anaerobically digested prior to application on land. The purpose of digestion is to convert bulky, odorous sludges to relatively inert material that can be rapidly dewatering. The important benefit of this process is a biogas production, too. It is proper to enlarge primary sludge production in a primary settler by adding some coagulation aids, with aim to increase a biogas production, as much as possible. The most common coagulant is alum, but presence of large quantities of aluminum salts in sludge has a harmful impact on digestion and digested sludge application. Some natural coagulants, that have a numerous advantages, can be used instead of alum. Natural coagulants could be extracted from a different plant material, and considering the fact that they are of organic nature, the biogas yield can be enhanced by their presence. A plant material that remains after extraction can be used as a feed. The aim of this paper is a consideration of potential environmental benefits of substitution of alum by natural coagulant extracted from common bean seeds in sewage wastewater treatment process.
18
Du, Weiwei, and Wayne Parker. "Liquid–gas partitioning of selected volatile organic sulfur compounds in anaerobically digested sludges." Water Science and Technology 66, no. 3 (August 1, 2012): 573–79. http://dx.doi.org/10.2166/wst.2012.207.
Abstract:
The gas phase partitioning of volatile organic sulfur compounds (VOSCs) in anaerobic sludge digesters contributes to odors and can impact upon the suitability of biogases for use in alternative energy recovery technologies. In the present study, effective Henry's law coefficients (H′) were estimated for methyl mercaptan (MM), dimethyl sulfide (DMS), and dimethyl disulfide (DMDS) in both deionized water and deactivated digested sludge. It was found that the complex matrix of digested sludge did not significantly affect the partitioning of VOSCs. Therefore, partitioning of VOSCs in digesters could be represented by their partitioning in clean water. A regression model was developed for the linear relationship between ln H′ and 1/T in the gas-water system. The H′ values of MM, DMS, and DMDS were able to be calculated over a temperature range of 12–58 °C.
19
Sekiguchi, Y., Y. Uyeno, A. Sunaga, H. Yoshida, and Y. Kamagata. "Sequence-specific cleavage of 16S rRNA for rapid and quantitative detection of particular groups of anaerobes in bioreactors." Water Science and Technology 52, no. 1-2 (July 1, 2005): 107–13. http://dx.doi.org/10.2166/wst.2005.0505.
Abstract:
We developed a rapid and simple method for rRNA-based quantitative detection of a specific group of microorganisms in complex ecosystems. The method relies on the sequence-specific scission of 16S rRNA with ribonuclease H (RNase H) and oligonucleotides that specifically hybridize with targeted rRNA molecules. RNAs from a complex community were first mixed with an oligonucleotide and were subsequently digested with RNase H to achieve sequence-dependent rRNA cleavage at the hybridization site. For the quantitative detection of targeted rRNAs, the resulting RNA fragment patterns were analyzed by gel-electrophoresis, which separated and quantified cleaved and intact rRNA fragments. This method enabled the quantitative detection of microbes in a complex microbial community by a relatively simple and fast experimental procedure. We then applied the cleavage method to actual anaerobic microbial communities such as digested sewage sludge and UASB sludges. The results demonstrated that the present method was fully applicable to anaerobic digestor ecosystems containing complex anaerobic microorganisms.
20
Dong, Qirong, Martha Dagnew, Jeff Cumin, and Wayne Parker. "Preliminary evaluation of biosolids characteristics for anaerobic membrane reactors treating municipal wastewaters." Water Science and Technology 72, no. 8 (July 13, 2015): 1446–54. http://dx.doi.org/10.2166/wst.2015.356.
Abstract:
This study assessed the characteristics of biosolids of a pilot-scale anaerobic membrane bioreactor (AnMBR) treating municipal wastewater. The production of total solids (TS) and volatile solids (VS) was comparable to that reported for the extended aeration system at solids residence time (SRT) longer than 40 days. The yields of TS and VS were reduced as SRT increased from 40 to 100 days and increased with the addition of 26 mg/L of FeCl3. The AnMBR destroyed 60–82% of the VS loading in feed wastewater and hence it was concluded the biosolids met the requirements for vector attraction reduction for land application. The concentrations of volatile suspended solids and total suspended solids in the sludge were less than those reported after anaerobic digestion of conventional primary and secondary sludge mixtures, and hence dewatering of the waste stream may be required for some applications. The nutrient content in terms of total Kjeldahl nitrogen and total phosphorus was similar to that of anaerobically digested municipal sludges. The dewaterability of the biosolids was poorer than that reported for sludges from aerobic treatment and anaerobically digested sludges. Dewaterability was improved by addition of FeCl3 and reduced SRT. The biosolids met standards for land application with regards to the concentration of heavy metals but would need further treatment to meet Class B pathogen indicator criteria.
21
WILD, S. "Chlorophenols in digested U.K. sewage sludges." Water Research 27, no. 10 (October 1993): 1527–34. http://dx.doi.org/10.1016/0043-1354(93)90097-2.
22
Lowe, Paul, Michael Brown, and Kathleen Hudson. "The influence of fibres on the structure of thermally dried sludge product." Water Science and Technology 34, no. 3-4 (August 1, 1996): 469–73. http://dx.doi.org/10.2166/wst.1996.0465.
Abstract:
There appears to be a limited experience world-wide in the application of thermal drying technology to processing raw undigested sludge. This limited experience has shown that the products from raw sludge processing have a much lower bulk density than those from digested sludge. The apparent reason for this phenomenon demonstrated by this work, is the high concentration of fibres in the raw undigested sludge. Different sludges show varying degrees of fibre concentration with a decrease in fibre content as the proportion of secondary sludge increases. The relationship between the bulk density of the product and the fibre content are given and this shows that as the fibre content increases the bulk density of the product will fall. It is recommended that a compaction/pelletisation stage is included in the process stream for high fibre sludges.
23
Anderson, B. C., and D. S. Mavinic. "Improvement in aerobic sludge digestion through pH control: initial assessment of pilot-scale studies." Canadian Journal of Civil Engineering 14, no. 4 (August 1, 1987): 477–84. http://dx.doi.org/10.1139/l87-072.
Abstract:
Waste-activated sludges from an extended-aeration, pilot-scale wastewater treatment facility and a high-rate, full-scale system were aerobically digested in 150 L pilot-scale digesters, operated in a semicontinuous (daily fill-and-draw) mode, at a standard 15-day solids retention time (SRT). To offset the mixed-liquor pH (MLpH) decrease normally encountered in these digesters (as a result of nitrification), hydrated lime and sodium bicarbonate were used in separate experiments to control MLpH in the series pH 6, 7, 8, and 9. Digester performance in the first stage of this work was assessed solely on the basis of reduction in total volatile suspended solids.The extended-aeration type sludge exhibited the greatest improvement in process performance under all pH-controlled conditions. Improvements in digestion efficiency of up to 80% over the uncontrolled reactors were noted. The use of lime resulted in greater digestion enhancement than did sodium bicarbonate with this sludge, without a significant increase in sludge solids production (owing to the low chemical doses required). Digestion efficiency of the high-rate type sludge was little improved (on a relative basis) with either chemical; however, absolute efficiencies in the individual digesters were, in some cases, nearly double those of the comparative extended-aeration sludge digesters. This difference appears to be a function of the process from which the digesting sludge originated, and seems to be influenced by the amount of easily oxidizable, endogenous substrate contained in the biomass. It was concluded that the extended-aeration type sludge was most amenable to enhanced digestion through pH control; as well, cost and process considerations made lime the chemical of choice. Key words: activated sludge, aerobic digestion, hydrated lime, mixed-liquor pH control, nitrification, process enhancement, pilot-scale, sodium bicarbonate.
24
Eskicioglu, C., K. J. Kennedy, and R. L. Droste. "Initial examination of microwave pretreatment on primary, secondary and mixed sludges before and after anaerobic digestion." Water Science and Technology 57, no. 3 (February 1, 2008): 311–17. http://dx.doi.org/10.2166/wst.2008.010.
Abstract:
The effects of microwave pretreatment on disintegration and mesophilic digestion of waste activated sludge (WAS), primary sludge (PS), combined (PS + WAS) sequencing batch reactor (SBR) sludge and anaerobically digested biocake were investigated by both household and bench scale industrial types microwaves at temperatures below and above boiling point. Pretreatment variables, temperature, intensity (cooking rate) and sludge concentration had statistically significant effects on solubilization. The microwave pretreatment also increased the bioavailability of sludge components under batch anaerobic digestion and enhanced the dewaterability of pretreated sludges after digestion. However, the level of improvements in solubilization and biodegradation from different waste sludges were different. While the largest improvement in ultimate biodegradation was observed in WAS, microwave irradiation only affected the rate of biodegradation of pretreated PS samples. Similarly, relatively lower solubilization ratios achieved for combined - SBR sludge was attributed to high sludge age of extended aeration SBR unit. It is possible that initial sludge characteristics may influence final pretreatment outcomes so that general statements of performance cannot always be made.
25
Hsiao, P. C., and S. L. Lo. "Extractability and fractionation of heavy metals in chemically treated sewage sludges." Water Science and Technology 44, no. 10 (November 1, 2001): 91–94. http://dx.doi.org/10.2166/wst.2001.0590.
Abstract:
Four chemically treated sludges, lime-treated (LS), lime/sodium silicate-treated (LSS), cement-treated (CS), and cement/sodium silicate-treated (CSS) were produced form the chemical treatment of aerobic digested sewage sludge cake, using lime, cement, and sodium silicate as additives. Ex tractability and fractionation of the heavy metals (Cu, Pb, Cr, and Zn) in these products and untreated sludge (S) were investigated using sequential extraction, single extraction, and 13C cross-polarization magic angle spinning nuclear magnetic resonance analysis (13C-NMR). These approaches revealed that chemical treatment of sewage sludge makes sludge Cu, Pb, and Cr more extractable. It was attributed to the irreversible dissolution of a portion of organics at very high pH during chemical treatment of sludge. The enhanced extraction of some metals having higher affinity to organics, e.g. Cu and Pb, from the chemically treated sludges was due to their complexion with the above soluble organics.
26
Anderson, B. C., and D. S. Mavinic. "Behaviour of volatile and nonvolatile suspended solids in the pilot-scale aerobic digestion of waste-activated sludges." Canadian Journal of Civil Engineering 20, no. 1 (February 1, 1993): 22–36. http://dx.doi.org/10.1139/l93-003.
Abstract:
Pilot-scale research into the characterization and enhancement of the aerobic digestion of waste-activated sludges was performed. Waste sludge from two sources was aerobically digested at varying operating temperatures; to offset the naturally occurring mixed liquor pH (MLpH) decrease due to nitrification, small amounts of Ca(OH)2 or NaHCO3 were added to maintain target MLpH levels of pH 6, 7, and 8. Results indicated that volatile mass reduction was severely curtailed at low MLpH, but could be significantly improved through MLpH control, with increases of > 100% in performance over the low MLpH reactor noted. However, the process was found to be very "sludge-specific", in that the two test sludges behaved quite differently under similar operating conditions. A separate mass balance on the nonvolatile sludge fraction illustrated the action of the controlling chemicals in terms of reduction in cell lysis; it was also observed that some precipitation of inorganic materials was occurring, depending on chemical type and dose. While it was not possible to suggest an optimized chemical and dose, it was concluded that this process had very real potential for full-scale implementation, as an effective and simple method for rehabilitation of poorly functioning digesters. Key words: aerobic sludge digestion, Ca(OH)2, enhancement, inhibition, mixed liquor pH control, NaHCO3, volatile and nonvolatile suspended solids.
27
Vesilind, P. Aarne, Seppo Wallinmaa, and C. James Martel. "Freeze–thaw sludge conditioning and double layer compression." Canadian Journal of Civil Engineering 18, no. 6 (December 1, 1991): 1078–83. http://dx.doi.org/10.1139/l91-130.
Abstract:
Freeze–thaw conditioning of water and wastewater sludges is known to be an effective and economical means of promoting dewatering when natural freezing is employed. When sludge freezes, both the suspended and dissolved solids are rejected by the growing ice front. Particles trapped in ice are known to have a very thin layer of water surrounding them and this water does not freeze at normal temperatures. Dissolved solids are thought to accumulate in this layer, causing an increase in the ionic strength of the water. This may cause compression of the double layer, leading to neutralization of repulsive forces, thus promoting aggregation. In order to test this hypothesis, ionic strength was increased by adding sodium chloride (NaCl) to water and wastewater sludges and measuring dewaterability (filtration) with the capillary suction time (CST) apparatus. Four different kinds of sludge were used: alum sludge (water treatment), waste-activated sludge, simultaneous precipitation, and anaerobically digested mixed sludge. Salinities of 0–20 000 mg/L as NaCl were tested with every sludge. No enhancement in dewaterability with freeze–thawed sludges of raised ionic strength compared to zero salinity was recorded, therefore the hypothesis of double layer compression being a major factor in freeze–thaw conditioning does not seem to be correct. Key words: sludge, freezing, coagulation, dewatering.
28
Langer, S. J., and R. Klute. "Rapid Mixing in Sludge Conditioning with Polymers." Water Science and Technology 28, no. 1 (July 1, 1993): 233–42. http://dx.doi.org/10.2166/wst.1993.0054.
Abstract:
The effect of mixing in sludge conditioning with polymers on the sludge dewaterability has been investigated by many researchers. What has been lacking so far are experimental data from a systematic variation of the rapid-mix conditions. Thus an experimental set-up was chosen to evaluate the effect of mixing by conditioning wastewater sludges in continuous mode rather than in batch-mode. The results show that the rapid-mix conditions have a strong effect on sludge dewaterability. Variations in the rotational speed of in-line stirring devices revealed that intense mixing is mandatory when conditioning anaerobically digested sludges. The results indicate that during a period of one second after polymer addition, mixing with maximum intensity (rotational speeds up to 1700 rpm) at the proper polymer dose does not lead to a deterioration in dewaterability. These findings could be confirmed by experiments with sludges from different treatment plants. The investigations with the different sludges revealed differences in the energy required for mixing in order to obtain optimal dewaterability. The mixing requirement is, in addition, strongly dependent on the polymer dose. High polymer doses are less sensitive to mixing, while at low doses, intense mixing becomes important Attempts have been made to describe the observed phenomena by considering the sludge rheology and the changes in rheology that take place in the reaction with the polymer.
29
Cheng, H. F., S. Y. Chen, and J. G. Lin. "Biodegradation of di-(2-ethylhexyl) phthalate in sewage sludge." Water Science and Technology 41, no. 12 (June 1, 2000): 1–6. http://dx.doi.org/10.2166/wst.2000.0227.
Abstract:
Di-(2-ethylhexyl) phthalate (DEHP) is widely used as a plasticizer in the production of polyvinyl chloride to impart flexibility to the product. Because of its mutagenicity and carcinogenicity, the presence of DEHP in sludge limits the application of sludge as a soil fertilizer. In this study, sludges were collected from three sewage treatment plants and thirteen wastewater treatment plants of different industries in Taiwan. A supercritical fluid extraction (SFE) was first established as an effective method for determining the concentration of DEHP in sludge. Laboratory-scale land-simulated experiments were performed to investigate the biodegradation of DEHP in sludge under various conditions (moisture, temperature, sunlight and ventilation). DEHP was found in aerobically and anaerobically digested sludges and their values significantly exceeded the restricted concentration of DEHP for sludge land application. DEHP was found to degrade in sludge under the conditions of good ventilation, sufficient sunlight and proper moisture. The indigenous microorganisms in the sludge appeared to dominate the biodegradation of DEHP in sludge. However about 70% of DEHP remained in sludge after 189 d indicating that DEHP is persistent in the environment.
30
Alcock, Ruth E., and Kevin C. Jones. "Polychlorinated biphenyls in digested UK sewage sludges." Chemosphere 26, no. 12 (June 1993): 2199–207. http://dx.doi.org/10.1016/0045-6535(93)90346-7.
31
Kolisch, G., and T. Rolfs. "Integrated sidestream treatment for enhanced enlargement of sewage plants." Water Science and Technology 41, no. 9 (May 1, 2000): 155–62. http://dx.doi.org/10.2166/wst.2000.0194.
Abstract:
The filtrates or centrates from dewatering of digested sludges cause high internal nitrogen loads on sewage treatment plants. Especially at poor inflow C:N ratios separate treatment of these sludge liquors can significantly relieve the biological treatment stage. We developed a new process for a biological sidestream treatment with primary sludge as the carbon source for denitrification. The process has beeen tested in laboratory-scale tests and by computer simulations. The stability of the process is being investigated in a full-scale application under practical conditions.
32
Hwa, Tay Joo, and S. Jeyaseelan. "Conditioning of oily sludges with municipal solid wastes incinerator fly ash." Water Science and Technology 35, no. 8 (April 1, 1997): 231–38. http://dx.doi.org/10.2166/wst.1997.0318.
Abstract:
Conditioning of sludges improves dewatering characteristics and reduces the quantity of sludge to be handled. Anaerobic digested sludge collected from a sewage treatment plant contained 1.8% to 8% oil. The increase of specific resistance and capillary suction time (CST) with increasing oil content observed in these samples indicates the interference of oil in dewatering. It has been found that addition of municipal solid wastes incinerator fly ash decreases the specific resistances and capillary suction times of oily sludges rapidly up to 3% dosage. Beyond 3% fly ash, the decrease is less significant and the solids content in the sludge cake increases. This optimum dosage remains the same for sludges with varying oil contents from 1.8% to 12%. The total suspended solids of filtrate decreases with fly ash dosage but the toxic concentrations of heavy metals increases considerably. However at the optimum dosage of 3%, concentrations of heavy metals are within the limits for discharging into the sewers. The correlations of CST with the dewatering characteristics such as specific resistance, filter yield and corrected filter yield are established. These correlations can be used to obtain a quick prediction on dewaterability.
33
Neis, U., K. Nickel, and A. Tiehm. "Enhancement of anaerobic sludge digestion by ultrasonic disintegration." Water Science and Technology 42, no. 9 (November 1, 2000): 73–80. http://dx.doi.org/10.2166/wst.2000.0174.
Abstract:
Biological cell lysis is known to be the rate limiting step of anaerobic sludge stabilization. Shear forces generated by high-power ultrasound can be used to disintegrate bacterial cells in sewage sludge. Thus the quantity of bioavailable dissolved organic substrate (Chemical Oxygen Demand) is significantly increased. As a result the subsequent sludge degradation is accelerated considerably. In our tests the fermentation process of sonicated waste activated sludge remained stable even at a very short digestion time of 4 days. The enhanced degradation rate resulted in a reduced volatile solids concentration of the digested sludges after the usual fermentation times.
34
Oake, R. J., C. S. Booker, and R. D. Davis. "Fractionation of Heavy Metals in Sewage Sludges." Water Science and Technology 17, no. 4-5 (April 1, 1985): 587–98. http://dx.doi.org/10.2166/wst.1985.0162.
Abstract:
Metals (Cd, Cr, Cu, Ni, Pb and Zn) have been fractionated in representative sewage sludges (primary, secondary, digested) by a sequential extraction procedure using KNO3 1M (removes the ‘exchangeable' fraction), KF 0.5M (‘sorbed'), Na4P2O7 0.1M (‘organic'), Na2EDTA 0.1M (‘carbonate') and HNO3 6M (‘sulphide'). Major differences according to sludge type were not seen. Cd occurred mainly in the ‘carbonate' fraction and 38–62% of Cr was in the ‘organic' fraction. 43–70% Cu was in the sulphide fraction whilst >40% of Ni was extracted in the ‘exchangeable/sorbed' fractions. Pb was found predominantly in the ‘organic' and ‘carbonate' fractions and Zn in the ‘organic' fraction. The complete extraction procedure removed 54–100% of the total metals content of the sludges. Changes in fractionation caused by drying, storage and time of extraction are reported. The results form the first part of a detailed investigation into the chemistry of metals in sewage sludge.
35
Campbell, H. W., and T. R. Bridle. "Conversion of Sludge to Oil: A Novel Approach to Sludge Management." Water Science and Technology 21, no. 10-11 (October 1, 1989): 1467–75. http://dx.doi.org/10.2166/wst.1989.0343.
Abstract:
Experiments at the Wastewater Technology Centre have shown that low temperature conversion of sludge to oil represents a promising alternative to sludge incineration. A 1kg/h bench-scale reactor produced oil yields ranging from a low of 13% for an anaerobically digested sludge to a high of 46% for a mixed raw sludge. Char yields ranged from 40 to 73% at the optimum operating temperatures. Preliminary results from a 40 kg/h pilot plant were similar to those obtained on the bench-scale system with the same sludges. The economics of the conversion process are compared with those for incineration. The impact of the “sludge to oil” technology on the design of sludge management systems is also discussed.
36
Novak, J. T., and C. Park. "Chemical conditioning of sludge." Water Science and Technology 49, no. 10 (May 1, 2004): 73–80. http://dx.doi.org/10.2166/wst.2004.0612.
Abstract:
With all the advances made in understanding the structure and composition of sewage sludges, chemical conditioning remains a trial and error process, both with regard to the type and dose of conditioner needed. Recent studies at Virginia Tech have found that biological floc consists of two types of biopolymer, material associated with iron and aluminium and material associated with calcium and magnesium. These materials behave differently when sludges undergo digestion. This results in very different material being released into solution during digestion and very different conditioning requirements. This study shows that the primary materials released during anaerobic digestion are proteins and coagulation of the colloidal protein fraction in solution is the primary mechanism for conditioning. For aerobically digested sludges, both proteins and polysaccharides make up the colloid fraction, which interferes with dewatering. This research also shows that the effectiveness of the digestion process as characterized by volatile solids destruction is directly related to the chemical dose required for conditioning. That is, as the solids destruction increases, the conditioning chemical requirement also increases. Well digested sludges dewater more poorly and require more conditioning chemical than those with less volatile solids destruction.
37
Huang, J., M. Elektorowicz, and J. A. Oleszkiewicz. "Dewatering and disinfection of aerobic and anaerobic sludge using an electrokinetic (EK) system." Water Science and Technology 57, no. 2 (January 1, 2008): 231–36. http://dx.doi.org/10.2166/wst.2008.009.
Abstract:
The objectives of the study were to upgrade sewage sludge to Class A Exceptional Quality biosolids (as defined by US EPA) using an electrokinetics dewatering system. The pathogens monitored were Salmonella spp, and fecal coliforms (FC). Ten bench-scale electrokinetic cells were set up for the disinfection of the following sludges: primary, secondary (attached growth culture and suspended culture), and anaerobically digested sludge. A conditioning liquid was also added to five cells. Blower system to aid in dewatering and drying was used in in four EK cells. Sludge characteristics such as water content, volatile solids content, sulfate and chloride ions concentrations, FC and Salmonella spp. before and after the tests were monitored. The highest total solids content (98% TS) was achieved in the cell with the low voltage gradient, in the presence of the conditioner and with the blower system. An average reduction by 50% of volatile solids was observed. The highest, 11 log-reduction of Salmonella spp. was observed in a cell with anaerobically digested sludge. No fecal coliforms were observed in any of the cells after EK treatment.
38
Qi, Y. N., S. Gillow, D. S. Herson, and S. K. Dentel. "Reactivation and/or growth of fecal coliform bacteria during centrifugal dewatering of anaerobically digested biosolids." Water Science and Technology 50, no. 9 (November 1, 2004): 115–20. http://dx.doi.org/10.2166/wst.2004.0549.
Abstract:
Fecal coliform bacteria are used as indicator organisms for the presence of pathogens. In sludges, it has often been assumed that the counts of fecal coliforms after digestion (where the sludges may also be called biosolids) are representative of the counts when the sludge is disposed or recycled, such as by land application. The possibility has been raised, however, that dewatering processes can lead to increased counts of fecal coliforms and, by inference, human pathogens. This paper presents data from previous studies of this possibility; the results were inconsistent but showed observable increases in fecal coliforms at one treatment plant. Additional studies were then performed at another treatment facility, which showed statistically significant increases in fecal coliform counts after dewatering and two days of aging. The increases exceeded two orders of magnitude and included two centrifuge types and two biosolids types. Artifacts of media type and enumeration method have been excluded, and shearing of the material by commercial blender did not produce the same effects.
39
Battistoni, P. "Pre-treatment, measurement execution procedure and waste characteristics in the rheology of sewage sludges and the digested organic fraction of municipal solid wastes." Water Science and Technology 36, no. 11 (December 1, 1997): 33–41. http://dx.doi.org/10.2166/wst.1997.0391.
Abstract:
The rheology of a wide range of sludges coming from wastewater treatment plants and from the digestion and codigestion process of sewage sludge and organic fraction of municipal solid waste (OFMSW) is measured. Sieve pre-treatment is necessary for selecting the solid fraction (<0.84 mm) in order to carry out measurement avoiding bob locking in a rotational viscosimeter. All sludges, except those from double phase digestion of source selected OFMSW, have a minimum of 80% TS and 70% TVS in this fraction. By using a plastic model, the flow curve offers a yield stress with a high standard deviation particularly at low solid content, while the rigidity coefficient s.d. is less than 10% at 90% probability. The plastic model can be proposed for all sludges since it offers a standard error of data fitting of less than 5%, in addition this model is not significantly different from the pseudo plastic one. Rheological properties cover a four order of magnitude range and follow a power type relation with TVS for the whole sector of sewage sludge and an exponential one for the OFMSW sector. Between 5–55°C, a positive temperature sensitivity is shown, while the activation energy is not significantly different from that of water. A high thixotropic nature is found in sewage and a low one in OFMSW sludge. A power relation with the TVS content is verified only for the sewage sludge sector.
40
Fraser, J. A. L., A. F. Godfree, and F. Jones. "Use of Peracetic Acid in Operational Sewage Sludge Disposal to Pasture." Water Science and Technology 17, no. 4-5 (April 1, 1985): 451–66. http://dx.doi.org/10.2166/wst.1985.0151.
Abstract:
Intestinal pathogens and parasites are a problem associated with the disposal of sewage sludge to pasture. Those of major importance are ova of the beef tapeworm (Taenia saginata) and Salmonella bacteria. Techniques for routine monitoring of pathogens and intestinal parasite levels in sludge together with design of simple methods for their removal have intensified, because disposal of sewage sludge to pasture is coming under increasing international surveillance. The performance during field trials of a proprietary peracetic acid compound (containing 36 to 40% w/w peracetic acid), hereafter referred to as PAA (100%), is described. These trials under operational conditions showed it to be a suitable bacterial and ovicidal agent for the disinfection of raw, digested and activated sludges. Concentrations ranging from 250 to 1000 mg PAA/l have achieved up to 99% inhibition of hatching and up to 100% destruction in viability of tapeworm embryos suspended in raw and digested sludges. Similarly these concentrations resulted in 5 log reductions in salmonellae seeded in raw sludge. A dose of 250 mg PAA/1 reduced salmonellae levels from 4600 organism/100cm3 to <30/100cm3 during gravity thickening of surplus activated sludge. Results from 46 tanker loads of consolidated surplus activated sludge revealed that salmonellae levels were reduced from 2400 organisms/100 cm3 to <30/100 cm3 at doses of 500, 400 and 300 mg PAA/1. At a lower dose of 150 mg PAA/1 levels were reduced to within a range of <30 to 430 organisms/100 cm3. At optimum disinfection concentrations for the destruction of both bacteria and parasites, PAA was rapidly utilised resulting in safe, readily biodegradable, non-toxic residuals. The technical and practical benefits, principals of disinfecting sludge and ecological safeguards are highlighted in this paper. Use is made of case histories to describe practical operating techniques.
41
Hwa, Tay Joo, and S. Jeyaseelan. "Comparison of lime and alum as oily sludge conditioners." Water Science and Technology 36, no. 12 (December 1, 1997): 117–24. http://dx.doi.org/10.2166/wst.1997.0438.
Abstract:
Chemical conditioning improves sludge dewatering. Choice of chemical conditioners is very much dependent on the characteristics of the sludges and the type of dewatering devices. Lime, alum, ferric chloride and polyelectrolytes are commonly used chemical conditioners. Anaerobic digested sludge samples collected from a sewage treatment plant with different oil contents varying from 1.8% to 8.0% by weight have been examined in the laboratory to find out their specific resistance, capillary suction time and filter yield. Lime and alum were used separately as conditioners. Different dosages of conditioner varying from 2% to 12% by weight were used to determine the optimum chemical dosage for varying oil contents. Lime dosages of about 6% were found to yield favourable characteristics. Addition of alum decreases the specific resistances and capillary suction times of oily sludges rapidly up to 4% dosages. Alum dosages beyond 4% only increase the solids content in the sludge cake and increase the sludge volume to be handled. A correlation between CST and specific resistance to filtration was established. CST can be measured easily and quickly in the laboratories. Using the CST and the correlation a quick prediction on dewaterability can be established.
42
Battistoni, P., G. Fava, C. Stanzini, F. Cecchi, and A. Bassetti. "Feed Characteristics and Digester Operative Conditions as Parameters Affecting the Rheology of Digested Municipal Solid Wastes." Water Science and Technology 27, no. 2 (January 1, 1993): 37–45. http://dx.doi.org/10.2166/wst.1993.0073.
Abstract:
The rheology of pre-composted and fresh organic fractions of municipal solid wastes (OFMSW) anaerobically digested in thermophilic range of temperature and different operative conditions is presented. Rheological properties are strongly influenced by feed characteristics and the biodEgradation achieved. The metabolization of complex substrates has been invoked to explain different behaviours. A semiempirical model of plastic viscosity with total volatile solids, organic loading rate removed and specific gas production before feeding is proposed. The fluid behaviour of OFMSW sludges where complex substrates exert a determinant role, is outlined by thixotropy and temperature effect.
43
Müller, J. "Disintegration as a key-step in sewage sludge treatment." Water Science and Technology 41, no. 8 (April 1, 2000): 123–30. http://dx.doi.org/10.2166/wst.2000.0151.
Abstract:
Fields of application of the mechanical sewage sludge disintegration are presented. Various methods of mechanical cell disintegration are described and the obtained results are compared. All methods are able to break up the flocs, but only some of them provide enough energy for the disruption of micro-organisms. The possible improvement of the anaerobic degradation process using raw sludge, excess sludge and digested sludge is shown. Excesssludge proves to be the most suitable. The use of disintegrated sludge as a carbon source for the denitrification is explained as a second field of application. External carbon sources can be substituted and the amount of sewage sludge to be disposed of is reduced at the same time. Foamingin digesters caused by filamentous micro-organisms can be reduced by disintegration of these sludges. Adsorbed gas bubbles are released and the settling properties of the sludge are improved. Another field of application is the solution of organic components of the sludge solids. The increased concentration of nitrogen and phosphorous in the supernatant causes recovery processes to be operated at a higher cost efficiency. A comparison of effort and advantages shows that disintegration is especially useful if there are problems in the sludge treatment process of the WTP.
44
Gülec, S. B., T. T. Onay, and A. Erdincler. "Determination of the remaining stabilization potential of landfilled solid waste by sludge addition." Water Science and Technology 42, no. 9 (November 1, 2000): 269–76. http://dx.doi.org/10.2166/wst.2000.0223.
Abstract:
Ultimate disposal of wastewater sludges is one of the most concerning steps of sludge management. As an alternative disposal, reuse of sludge as a soil conditioner or fertilizer has had some success. Another alternative is the addition of sludge to the solid waste landfills. Many researchers have studied the effects of sludge addition to the solid waste stabilization in landfills. However, part of the researchers found positive effects, while others found either negative effects or no effects at all. This study investigates the remaining stabilization potential of the solid waste retrieved from an operating landfill by sludge addition. Determination of the remaining stabilization potential of landfilled solid waste is an important issue in solid waste management. In this study, the further stabilization of landfilled solid waste is achieved by the addition of anaerobically digested sludge to the solid waste with different sludge to waste ratios. Four 10-litre laboratory-scale batch digesters operated under constant temperature of 34°C are used in the experiments. One of the digesters was the control unit operated without any sludge addition. The other three digesters had different sludge to waste ratios; 1:9, 1:6, 1:4 (on wet basis) respectively, in order to find the optimum ratio for the solid waste stabilization. The comparison of gas production and quality and other indicator parameters provided an opportunity to determine the remaining stabilization potential and its significance. The results are translated in terms of conventional landfill practices, as well as emerging technologies for innovative sludge management.
45
Wilson, Susan C., Victoria Burnett, Keith S. Waterhouse, and Kevin C. Jones. "Volatile organic compounds in digested United Kingdom sewage sludges." Environmental Science & Technology 28, no. 2 (February 1994): 259–66. http://dx.doi.org/10.1021/es00051a012.
46
Batista, Jacimaria R., and Hyunju Jeong. "Prediction of Struvite Formation Potential in EBPR Digested Sludges." Proceedings of the Water Environment Federation 2006, no. 7 (January 1, 2006): 5185–96. http://dx.doi.org/10.2175/193864706783763372.
47
Winter, P., and S. C. Duckham. "Analaysis of volatile odour compounds in digested sewage sludge and aged sewage sludge cake." Water Science and Technology 41, no. 6 (March 1, 2000): 73–80. http://dx.doi.org/10.2166/wst.2000.0095.
Abstract:
A number of malodorous compounds were identified in digested sludge and the corresponding sludge cakes. The major components included a number of sulfides. The levels of these compounds were monitored in order to investigate the influence of the sludge treatment process and length of cake storage on the malodour of treated sewage sludge. Two sewage treatment works (STWs) were surveyed. One of the works (Site B) produced very malodorous sludge cake, whilst the other produced a much less odorous cake (Site A). The analysis consisted of purge and trap sampling of liquefied samples followed by gas chromatography-mass spectrometry (GC-MS). Afteran initial screening of samples, by full mass scan GC-MS analysis, targetcompounds were identified for quantification. Sulfide levels inthe majority of the liquid digested sludges were significantly lower than that in sludge cakes. Large differences in the level of sulfides were found in stockpiled sludge cakes. The majority of malodorous sludge cakes had higher sulfide levels than less odorous sludge cakes. The most abundant compounds were dimethylsulfide, dimethyldisulfide and dimethyltrisulfide. Thehighest sulfide levels were found during the first month of stockpiling. Whenthe odour threshold concentration of these compounds was taken into account and odour unit values were calculated, dimethyltrisulfide was found to have a proportionally greater impact on odour than any of the other compounds studied. The use of sulfide levels as indicators of malodour formation and possible strategies for reducing odour in stockpiled sludge cake are discussed.
48
Yang, Y., Y. Q. Zhao, A. O. Babatunde, and P. Kearney. "Two strategies for phosphorus removal from reject water of municipal wastewater treatment plant using alum sludge." Water Science and Technology 60, no. 12 (December 1, 2009): 3181–88. http://dx.doi.org/10.2166/wst.2009.609.
Abstract:
In view of the well recognized need of reject water treatment in MWWTP (municipal wastewater treatment plant), this paper outlines two strategies for P removal from reject water using alum sludge, which is produced as by-product in drinking water treatment plant when aluminium sulphate is used for flocculating raw waters. One strategy is the use of the alum sludge in liquid form for co-conditioning and dewatering with the anaerobically digested activated sludge in MWWTP. The other strategy involves the use of the dewatered alum sludge cakes in a fixed bed for P immobilization from the reject water that refers to the mixture of the supernatant of the sludge thickening process and the supernatant of the anaerobically digested sludge. Experimental trials have demonstrated that the alum sludge can efficiently reduce P level in reject water. The co-conditioning strategy could reduce P from 597–675 mg P/L to 0.14–3.20 mg P/L in the supernatant of the sewage sludge while the organic polymer dosage for the conditioning of the mixed sludges would also be significantly reduced. The second strategy of reject water filtration with alum sludge bed has shown a good performance of P reduction. The alum sludge has P-adsorption capacity of 31 mg-P/g-sludge, which was tested under filtration velocity of 1.0 m/h. The two strategies highlight the beneficial utilization of alum sludge in wastewater treatment process in MWWTP, thus converting the alum sludge as a useful material, rather than a waste for landfill.
49
Beauchesne, I., S. Barnabé, D. G. Cooper, and J. A. Nicell. "Plasticizers and related toxic degradation products in wastewater sludges." Water Science and Technology 57, no. 3 (February 1, 2008): 367–74. http://dx.doi.org/10.2166/wst.2008.001.
Abstract:
Plasticizers can persist during the treatment of wastewaters in sewage treatment plants (STPs) and can be discharged in effluents and/or accumulated in sewage sludges. For example, di-2-ethylhexyl phthalate (DEHP) is a common plasticizer that is now considered a priority pollutant and is known to accumulate in sludges. This may add constraints to the exploitation of the beneficial uses of sludges that contain significant quantities of plasticizers. Recently, it was demonstrated in studies with pure cultures that the biodegradation of plasticizers including DEHP and di-ethylhexyl adipate (DEHA) generates toxic metabolites including 2-ethylhexanoic acid, 2-ethylhexanol, and 2-ethylhexanal. However, the environmental impacts and fate of the degradation products arising from plasticizers are unknown. Therefore, this work investigated the concentrations of DEHP and DEHA and their metabolites in the sludges from several STPs in Quebec, Canada. DEHP and DEHA were found in concentrations ranging from 15 to 346 mg kg−1 and 4 to 743 mg kg−1, respectively, in primary, secondary, digested, dewatered or dried sludges. Metabolites were detected in almost all sludges, except those that had undergone a drying process at high temperature. It is concluded that sludges can represent significant sources of plasticizers and their toxic metabolites in the environment.
50
Merzari, Fabio, Jillian Goldfarb, Gianni Andreottola, Tanja Mimmo, Maurizio Volpe, and Luca Fiori. "Hydrothermal Carbonization as a Strategy for Sewage Sludge Management: Influence of Process Withdrawal Point on Hydrochar Properties." Energies 13, no. 11 (June 5, 2020): 2890. http://dx.doi.org/10.3390/en13112890.
Abstract:
Conventional activated sludge systems, still widely used to treat wastewater, produce large amounts of solid waste that is commonly landfilled or incinerated. This study addresses the potential use of Hydrothermal Carbonization (HTC) to valorize sewage sludge residues examining the properties of hydrochars depending on HTC process conditions and sewage sludge withdrawal point. With increasing HTC severity (process residence time and temperature), solid yield, total Chemical Oxygen Demand (COD) and solid pH decrease while ash content increases. Hydrochars produced from primary (thickened) and secondary (digested and dewatered) sludge show peculiar distinct properties. Hydrochars produced from thickened sludge show good fuel properties in terms of Higher Heating Value (HHV) and reduced ash content. However, relatively high volatile matter and O:C and H:C ratios result in thermal reactivity significantly higher than typical coals. Both series of carbonized secondary sludges show neutral pH, low COD, enhanced phosphorous content and low heavy metals concentration: as a whole, they show properties compatible with their use as soil amendments.