Dissertations / Theses on the topic 'Sewage sludge anaerobically digested'

Thesis (Ph.D.)--University of Delaware, 2008.
Principal faculty advisors: Steven K. Dentel, Dept. of Civil & Environmental Engineering; and Diane S. Herson, Dept. of Biological Sciences. Includes bibliographical references.

A study of the anaerobically digested sludge form a full-scale biological phosphorus removal (BPR) plant (York River Wastewater Treatment Plant, York River, Va.) was conducted to determine the effects of BPR on sludge characteristics and conditioning requirements. Data collected from the plant indicated that both the total and soluble phosphorus (P) concentrations in the anaerobically digested sludge increased dramatically with the initiation of BPR. Accompanying this increase in total P was an increase in the total concentrations of magnesium and potassium content of the sludge, supporting the observations that these ions are coâ transported with P during the accumulation and release of P by P accumulating organisms. The majority of the phosphate present in the pre- and post- BPR anaerobically digested sludges was bound by calcium, magnesium, and iron phosphorus precipitates including hydroxyapatite, struvite, and vivianite. Calcium phosphorus precipitates were the most prevalent in both sludges, but the percentage of magnesium phosphorus precipitates increased with the onset of BPR. Cationic organic polymer conditioning dosages needed to achieve acceptable sludge dewatering rates for the post-BPR sludge were similar to those required by the pre-BPR sludge. The cationic organic polymer used to condition these sludges was ineffective in removing excess phosphate; therefore, the addition of either one or both of the inorganic chemicals ferric chloride and calcium hydroxide was required to remove soluble phosphorus. Conditioning with either ferric chloride or calcium hydroxide alone was not effective in achieving acceptable dewatering rates; however, when used together the chemicals produced acceptable dewatering rates and soluble P removal from the post-BPR sludge.
Master of Science

In designated nutrient-sensitive areas, phosphorus must be removed from sewage before it is discharged to the receiving water body. Phosphorus-rich sludge is generated, which is usually digested anaerobically prior to disposal. This research investigated the effect of phosphorus enrichment on metal and phosphorus fractionation in anaerobically digested sludge. The use of two complementary sequential chemical extraction procedures to measure phosphorus and metal fractionation, was a key focus of the research. The fractionation procedures were tested by sequentially extracting inorganic compounds (phosphates, sulphides and carbonates) which showed that the operationally defined metal and phosphorus fractions were not always representative of precise metal phases. Species were tentatively assigned to metal and phosphorus fractions using model compound results. Laboratory-scale batch anaerobic digestion experiments were performed, in which model compounds were used to simulate conditions of soluble and insoluble phosphorus enrichment. Soluble phosphorus at concentrations of 500 mg/l or greater was found to retard volatile solids removal and methane production in the laboratory digesters. Soluble phosphorus enrichment facilitated precipitation of calcium, magnesium and manganese but increased trace metal solubility, particularly that of chromium. Enrichment of digesters with Na2HP04 and MgCb caused struvite to precipitate in digesters containing 1000 mg/l of additional phosphorus. FeP04 enrichment of digested sludge showed that ferric iron was reduced to ferrous iron, releasing soluble phosphorus into the digester. Most of the phosphorus was reprecipitated as ferrous phosphate, causing co-precipitation of magnesium, manganese and cobalt. By contrast, A1P04 added to the digesters was stable in the sludge. Full-scale CPR sludge digestion (Fe2(S04)3 dosing) caused soluble phosphorus in the digester to decrease below 0.05 mg/l. Phosphorus remained associated with iron in the sludge fraction but soluble calcium and magnesium concentrations in the full-scale digester increased as a result of CPR sludge digestion. Comparison of laboratory and full-scale results showed that the fate of iron-precipitated phosphorus in digested sludge was primarily dependent pn the molar ratio of Fe:P in the sludge. Full-scale BPR sludge digestion showed high concentrations of soluble phosphorus in the digester and some struvite precipitation, although phosphorus was precipitated primarily as calcium phosphate, as was found to occur in the laboratory digesters simulating BPR sludge digestion.

The significant increase in the sewage sludge production in treatment plants makes anaerobic digestion more important as a stabilization process. However hydrolysis is the rate-limiting step of anaerobic digestion because of the semirigid structure of the microbial cells. Pretreatment of waste activated sludge (WAS) leads to disruption of cell walls and release of extracellular and intracellular materials. Therefore biodegradability of sludge will be improved in terms of more biogas production and sludge minimization. Among the pretreatment methods, alkaline, thermal and thermochemical pretreatments are effectual ones. Considering the effect of thermal pretreatment, microwave technology in which the sample reaches to elevated temperatures very rapidly is a very new pretreatment method. However no previous research has been conducted to test the effectiveness of microwave (MW) irradiation combined with alkaline pretreatment. Since both of these techniques seem to be highly effective, their combination can act synergistically and even more efficient method can be obtained. Therefore the main objective of this study was to investigate the effect of combination of a chemical method (alkaline pretreatment) and a physical method (microwave irradiation) in improving anaerobic digestion of WAS. In the first part of the study, alkaline and MW pretreatment methods were examined separately, then their combinations were investigated for the first time in the literature in terms of COD solubilization, turbidity and CST. Highest SCOD was achieved with the combined method of MW+pH-12. In the second part, based on the results obtained in the first part, alkaline pretreatments of pH-10 and pH-12
MW pretreatment alone and combined pretreatments of MW+pH-10 and MW+pH-12 pretreated WAS samples were anaerobically digested in small scale batch anaerobic reactors. In correlation with the highest protein and carbohydrate releases with MW+pH-12, highest total gas and methane productions were achieved with MW+pH-12 pretreatment reactor with 16.3% and 18.9% improvements over control reactor, respectively. Finally the performance of MW+pH-12 pretreatment was examined with 2L anaerobic semi-continuous reactors. 43.5% and 53.2% improvements were obtained in daily total gas and methane productions. TS, VS and TCOD reductions were improved by 24.9%, 35.4% and 30.3%, respectively. Pretreated digested sludge had 22% improved dewaterability than non-pretreated digested sludge. Higher SCOD and NH3-N concentrations were measured in the effluent of pretreated digested sludge
however, PO4-P concentration did not vary so much. Heavy metal concentrations of all digested sludges met Soil Pollution Control Regulation Standards. Finally a simple cost calculation was done for a MW+pH-12 pretreatment of WAS for a fictitious WWTP. Results showed that, WWTP can move into profit in 5.5 years.

Inactivation of bacteriophages MS-2 and PRD1, and poliovirus type 1 were measured in Pima Clay Loam and Brazito Sandy Loam soils amended with anaerobically digested sewage sludge. Inactivation was determined at 15°C, 27°C, and 40°C with soils maintained at 30% moisture, and amended soils exposed to evaporation. No inactivation of PRD1 was observed within 30 days and 16 days at 15°C and 27°C respectively with little inactivation after 7 days at 40°C. Inactivation of MS-2 and poliovirus was approximately 2 fold greater at 27°C compared to 16°C. At 40°C neither virus was recovered 24 hours after sludge amendment. Evaporation to less than 5% soil moisture resulted in rapid loss of titer for all three viruses regardless of temperature. Survival of MS-2 and poliovirus 1 in sludge amended fields (15°C) was longer than comparable laboratory studies. None of the viruses were recovered in fields amended during the summer (33°C) after 7 days. A method was also developed to remove cell culture toxic components from these soils.

This thesis presented the dewatering performance improvement of anaerobically digested sludge with novel application and assessment of conditioning aids. The effectiveness of sludge conditioning was evaluated by batch experiments using a series of 250-mL jar test beakers. The optimal dosage was found at 15–20 g/kg chitosan with enhanced dewaterability and rheological behaviour. The dual-chemical conditioning results indicate a higher rate of water removal at the expense of dry solids content compared to single conditioning.

Before being discharged in a water body, municipal wastewater undergoes filtration, sedimentation, biological oxidation, and nutrient abatement in a wastewater treatment plant (WWTP); typically, the resulting sewage sludge is anaerobically digested for biomethane production. The sludge management practices currently involve landfill disposal and energy-intensive treatments, such as incineration or co-incineration, while agricultural soil applications and composting account for a minor amount. From a sustainability point of view, landfill disposal and incineration of sludge are not efficient in terms of energy consumption or waste material recovery. Thus, scientific research led to the development of innovative technologies aiming to decrease the sewage sludge volume and odour issues and to promote the valorization of the feedstock. In particular, the process described in this thesis, devised by HBI Srl., combines hydrothermal carbonization (HTC) of sewage sludge with hydrochar gasification. The HTC products are hydrochar and HTC liquor; the former can be used for energy production and carbon capture and storage, while the latter can increase the methanogenic sludge potential. Hydrochar then undergoes gasification in an upstream (counter-current) fixed-bed reactor, resulting in syngas and ash production. Once purified from fly ash by a cyclone, the produced syngas is nowadays burned in a torch. Future applications might involve heat and power cogeneration and the production of useful platform chemicals. Since the water excess is recirculated back to the WWTP, the only process by-product is the gasification ash, which can be potentially valorized as a fertilizer additive thanks to its significantly high content of phosphorous and relatively low content of heavy metals. Lastly, CHNS, SEM-EDX, TGA were performed on digested sewage sludge and hydrochar samples, confirming the potential of this promising sludge valorization technology.

The objective of this research was to assess specific side-stream processes for biodegradation and precipitation of dissolved nutrients in dewatering centrate and support the seamless integration of an anaerobic digester (AD) into a biological nutrient removal wastewater treatment plant (WWTP). Anaerobic digestion processes release reactive and non-reactive dissolved nutrients which are returned to the mainstream treatment process in the dewatering centrate. Conventional side-stream treatment processes are typically designed for removal of reactive nutrients (ie, nitrate/nitrite, ammonia and orthophosphate). However, many WWTPs with low total nitrogen and total phosphorus criteria will also be impacted by the non-reactive, difficult-to-degrade nutrient forms such as polyphosphates (poly-P), dissolved organic phosphorus (DOP) and dissolved organic nitrogen (DON). In this study, characterization was made of a conventional suspended growth deammonification treatment (Anammox) process for transforming poly-P, DOP and DON in two types of dewatering centrate. The first centrate feed studied was from the full-scale Annacis Island WWTP (AIWWTP), Canada. The second centrate feed was from a lab-scale AD fed waste sludge from the existing City of Kelowna Wastewater Treatment Facility (KWTF), Canada. The Anammox process showed similar treatment characteristics for both the KWTF and AIWWTP centrates with excellent DON removal and poor non-reactive dissolved phosphorus (NRDP) removal. A statistical comparison of the DOP and poly-P through the Anammox process suggests that DOP has a higher biodegradation potential. Utilization of a post-Anammox, poly aluminum chloride chemical dosing, optimized based on zeta potential, was able to achieve the objective of precipitating residual DON and NRDP and producing an effluent with lower dissolved nutrients than the pre-digestion KWTF dewatering centrate scenario. Additional testing was conducted on final effluent to characterize the dissolved phosphorus and determine an optimal coagulant dose. The testing suggests that the dissolved phosphorus in effluent could be associated with colloidal dissolved organic matter (DOM). Furthermore, coagulant batch dosing experiments using poly aluminium chloride (PACL) and poly epichlorohydrin amine (polyepiamine) provides strong support for the use of zeta potential measurements as a way to optimize coagulant dose.
Applied Science, Faculty of
Engineering, School of (Okanagan)
Graduate

Water resources in Florida have been severely degraded by eutrophic conditions, resulting toxic algae blooms, which negatively affect health and tourism. Eutrophication, or excessive amount of phosphorus (P) and nitrogen (N) in water, overstimulates the production of aquatic plants, depletes dissolved oxygen, and deteriorates the aquatic environment. However, phosphorus is a non-renewable resource essential for all living organisms. In fact, more than half of the total demand for P globally is to supply the food industry, which has concerningly accelerated the depletion rates of phosphate reserves. In many wastewater treatment plants (WWTPs), the enhanced biological phosphorus removal (EBPR) approach has been employed to achieve high phosphorus removals from wastewater through phosphate-accumulating organisms (PAOs). However, during either anaerobic or aerobic digestion of EBPR sludge, stored polyphosphates are released and carried into the sidestream, which is typically returned to the headworks of the main treatment facility, thereby recycling phosphorus back into the system. This treatment train is highly inefficient because nutrients rather are recirculated rather than recovered. Struvite (MgNH4PO4•6H2O) is precipitated in oversaturated aqueous solutions with equal molar concentrations of magnesium, ammonium, and phosphate. The controlled crystallization of struvite may be applied to remove phosphorus and some ammonium from sidestreams, which is the liquid portion of the digester effluent. Struvite can be employed as a sustainable slow-release fertilizer due to its low solubility in water. This offers the opportunity of marketing the struvite produced under controlled conditions and creating a revenue for the utility. The specific research objectives of this thesis are (1) to investigate different possible operating conditions under which anaerobically digested sludge from EBPR facilities might be treated through struvite precipitation; (2) to quantify the removal of N and P from sidestreams from anaerobically digested EBPR sludge via struvite precipitation and assess the composition of the precipitate obtained; and (3) to generate a cost analysis to assess the trade-offs between the capital and operation and maintenance (O&M) costs of struvite production and the benefits such as reduced chemical use and production of a slow-release fertilizer. The main parameters affecting struvite precipitation are the Mg2+ to PO43- molar ratio, pH, temperature, mixing speed, hydraulic retention time (HRT), and the seed quantity added to promote nucleation. Different operating conditions within these parameters were batch-tested as part of this study using sidestream from the pilot-scale anaerobic digester (AD) fed from Falkenburg Advanced Wastewater Treatment Plant (FAWWTP) EBPR sludge. Additionally, the effect of temperature and pH were investigated using Visual MINTEQ simulations. Analysis of Variance (ANOVA) was employed to investigate the variance within the removals from the centrate obtained for phosphate, ammonium, magnesium, and calcium. The chemical composition of the solids collected after employing the selected operating conditions was analyzed by powder X-ray diffraction (PXRD). The results for the batch tests performed as part of this thesis were quantified in terms of the removals of phosphate, ammonium, magnesium, and calcium from the centrate. The greatest amount of phosphate removal was achieved by operating the struvite reactor at 4.0 mmol of Mg2+ per mmole of PO43-. The other molar ratios tested were 1.0, 2.0, and 3.0. Visual inspection of the data showed significant variability in removals of ammonium, calcium, and magnesium, which are likely to be correlated with the highly variable influent concentrations into the struvite reactor. In this case, ANOVA will require larger data sets to accurately analyze variance in the results. The statistical results given by ANOVA for the pH suggests that the main species to contribute with struvite being precipitated are statistically stable within the tested pH values of 8.5, 9.0, and 9.5. The results obtained by the simulation using Visual MINTEQ indicated that maximum saturation as function of pH takes place at a pH between 9.5 and 10.0. The ANOVA for the mixing speed showed that significant amounts of ammonium were removed at higher mixing speeds. This is likely due ammonium being volatilized, which is enhanced by turbulence. Magnesium and phosphate showed lower removals at higher mixing speeds, suggesting that too high mixing speeds will promote struvite seed dissolution. ANOVA identified NH4+ and Ca2+ as the species significantly impacted by modifying the HRT from 8 to 20 minutes. This suggests that prolonged HRT promotes inorganic nitrogen species to volatilize. It is likely that at higher HRT, tricalcium phosphates (TCP) or other favored calcium species coprecipitated together with struvite. Regarding the added struvite seed for nucleation, the greatest removals of ammonium, magnesium, and, phosphate were observed when 1g/L of struvite seed was added. The results also indicated that adding 5 and 10 g/L was an excessive amount of seed, which ended up contributing significantly to more nutrients into the centrate rather than precipitating them. The results also suggested that the struvite crystals formed in the sidestream by secondary nucleation, since removals close to zero were reached after adding no seed. The optimum temperature identified by the simulation in Visual MINTEQ was 21°C. Operating the struvite reactor under the optimal conditions identified in the batch tests, resulted in an average of 99% total P (TP) and 17% total N (TN) removals. The precipitate molar composition for [Mg2+:NH4+:PO43-] was equal to [2:2:1] based on the concentrations that disappeared from the aqueous solution, suggesting that other minerals coprecipitated with struvite. Visual MINTEQ predicted that together with struvite, CaHPO4 and CaHPO4•2H2O will also precipitate under the tested conditions. However, given the obtained ratio it is likely that other unpredicted species by Visual MINTEQ, such as magnesium carbonates or magnesium hydroxide coprecipitated with struvite. PXRD analysis also revealed that the sample was likely contaminated struvite, although the specific contaminants were not identified. A cost analysis was performed to distinguish the economic feasibility of incorporating a struvite harvesting system to treat the anaerobically digested sidestream from the Biosolids Management Facility (BMF) within the Northwest Regional Water Reclamation Facility (NWRWRF). Three different scenarios were evaluated; in Scenario (1) Ostara® Nutrient Recovery Technologies Inc. (Ostara®) evaluated the production of struvite from anaerobically digested EBPR sidestream using a fluidized reactor. In Scenario (2), Ostara® evaluated the production of struvite in a fluidized bed reactor by employing Waste Activated Sludge Stripping to Remove Internal Phosphorus (WASSTRIP™) in a mixture of post-anaerobic digestion centrate and pre-digester thickener liquor. Scenario (3) was addressed by Schwing Bioset Inc. (SBI) for a continuously-stirred reactor followed by a struvite harvesting system. Scenario (2) offers the highest TP and TN recoveries through WASSTRIP™ release due to the additional mass of phosphorus that is sent to the phosphorus recovery process. Therefore, although Scenario (2) has the highest total capital costs ($5M) it also has the shortest payback period (18 years). Scenarios (1) and Scenario (3) have similar payback periods (22-23 years) but very different total capital costs. The annual savings by producing struvite in Scenario (3) is $40K, which is about 30% less than producing struvite in Scenario (1). This is probably because the only savings considered under Scenario (3) were the lower alum usage and the fertilizer revenue; however, the savings by producing class A biosolids, were not accounted for. Consequently, the reduced total capital cost of $960K and the annual payment amount per interest period close to $80K, positioned Scenario (3) as the more feasible one, considering 20 years as the expected life of the asset at a 5% interest rate.

This thesis reports on investigations that have contributed to an advancement in the applied and fundamental understanding on how the nature, related storage and processing of digested sewage sludge can influence polymer conditioning and dewatering. The work concentrated more specifically on evaluating the impact of thermal hydrolysis as a pre-treatment to anaerobic digestion (AD) of mainly secondary sewage sludges (Advanced AD, AAD plants) in comparison with conventional mesophilic AD (CMAD) on conditioning and dewatering of the digestate, as this knowledge seemed to be lacking for an AAD technology that is increasingly being implemented. An additional contribution to knowledge from this study relates to the evaluation of how polymer conditioning and dewatering of digested sludges could be monitored using rheometric measurements. It was concluded that digested sludge biofloc characteristics (size, shear viscosity and organic matter composition) affected the most the conditioning and dewatering results but these varied depending on the process conditions i.e. AAD versus CMAD and digestate handling conditions. The reduction in particle size and shear viscosity (η[0.1 s-1]) per g Total Solids as well as the increased solubilization of protein, organically bound nitrogen and chemical oxygen demand of the digestates which contributed to the increased conditioning requirements affected also the dewatering rate and the strength of the flocs produced after conditioning. The changes in the digested sludge biofloc characteristics were detected by rheometric measurements which were well correlated with changes in organic matter composition and polymer conditioning requirements (r of 0.9 and 0.8). It was proposed that the variations in η[0.1 s-1] and organic matter content such as soluble protein could be used to predict polymer dose requirements to achieve good filterability (R2 of 0.7; significance F and p < 0.05). Future work is however required in order to consolidate these findings by monitoring conditioning, dewatering and η[0.1 s-1] of the digestate at full scale.

Biogas, a mixture of methane and carbon dioxide, is produced in the anaerobic digestion of sewage sludge. After anaerobic digestion, the digested sludge is often allowed to degas for one or two days. This gas is seldom utilised, but if the degassing could be accelerated, utilisation would be easier. Ultrasound can be used as a pretreatment method for waste activated sludge. It has a disintegrating effect on the sludge and causes lysis of bacteria in the sludge. It also speeds up the hydrolysis; the limiting step of anaerobic digestion of waste activated sludge. Ultrasound can be used to degas waterbased liquids. Ultrasonic degassing of sewage sludge has not been examined previously. The present study aims to investigate the effect of ultrasound on waste activated sludge as well as the potential of ultrasound to speed up the degassing of digested sludge. A semi-continuous, lab-scale digestion experiment was performed with four reactors: two receiving untreated sludge and two receiving treated sludge. The effect of the sonicator was 420 W and the treatment time was 6 min, which corresponds to an energy input of 8.4 kWh/m³. Total solids (TS) of the waste activated sludge was ~3.5 %. The ultrasonic treatment caused an increase in gas production of 13 %. There was no difference in methane content. The concentration of filterable chemical oxygen demand (fCOD) increased 375 %, or from 2.8 % to 11 % of total COD. In terms of energy loss/gain the increase in gas production resulted in a loss of 2.7 kWh/m³, i.e. more energy is needed to treat the sludge than the potential energy of the increased gas production. However, if the sludge is thickened to a TS >5 %, a net energy gain should be reached. The effect of ultrasound on the degassing of digested sludge was examined in three barrels. The degassing was measured with and without circulation as well as with ultrasonic treatment. The digested sludge had a gas emission rate of 115 L/(m³ day). No direct burst of gas occurred due to ultrasonic treatment. Over two days more gas was emitted from the barrel equipped with ultrasound, probably due to an induced post-digestion. Thus, ultrasonic pretreatment of waste activated sludge increases the biogas yield. It is inconclusive, whether ultrasonic treatment of digested sludge effects the degassing or not.

Biogas is produced when organic material is broken down in oxygen-free (anaerobic) conditions. This process is called anaerobic digestion and is used in most large and medium-sized municipal wastewater treatment plants in Sweden. In the wastewater treatment sewage sludge is obtained, from the mecanical-, biological and chemical treatment step, which contains decomposable organic material. The sludge is pumped into a digester, which is an airtight container. In the digester raw biogas, consisting of methane and carbon dioxide, is produced. The material that comes out of the digester is a nutrient rich residue (digestate) which can be used as a fertilizer or soil conditioner. The purpose of this study was to explore ways to increase the biogas production that takes place at the municipal wastewater treatment plants by either co-digestion of sewage sludge with microalgae from a possible future biological purification steps or to use two digestion stages in series with different operating temperatures, mesophilic (37ºC) followed by a thermophilic digestion (55ºC). The challenges with these methods, which are also taken into consideration in the studies, were changes in the dewaterability of the digestate, system efficiency regarding electricity and heat consumption, the ability to recycle nutrients, changes in the carbon footprint from the treatment plant, change of the pollution level in the digestate and the ability to create a sanitization method for the digestate. The results from the first part showed in both batch digestability tests and continuous anaerobic digestion experiment that microalgae cultivated on wastewater can be a feasible feedstock for anaerobic co-digestion with sewage sludge. Microalgae improved the biogas production in mesophilic conditions but not in thermophilic digestion. In the semi-continous experiment, with the addition of a natural mix of microalgae grown from wastewater to sewage sludge, the specific methane production was enhanced with 39 % for every gram organic matter reduced. The specific methane production for every gram added organic matter to the reactors were 9% lower in the digester where microalgae had been added. When microalgae were added the total digestibility was reduced compared to the reference digestion with only sewage sludge. Filterability tests indicated that the addition of microalgae enhanced the dewaterability of the digested sludge. Heavy metal levels in the microalgae substrate were much higher than in the sludge which could restrict the utilization of the digestate on arable land in a possible future full scale application. The results in the second part showed that the process solution could be a self-sufficient sanitation method. The highest organic loading rates tested in this study were in the range causing an unstable process due to high ammonia levels The thermophilic digestion gave the sludge worse dewaterability. However, a subsequent aeration step could improve the properties again.

The master’s thesis is focused on the issue of solar drying of sewage sludge. The sludge management of wastewater treatment plants is described in the first part of this thesis. This theoretical part also deals with description of drying and dryers used for sludge treatment. The second part of the thesis is focused on the experimental solar drying of sewage sludge and the evaluation of the results.

Thesis (PhD (Food Science))--University of Stellenbosch, 2009.
In the absence of anaerobic granules, anaerobically digested sewage sludge is frequently used to seed industrial upflow anaerobic sludge blanket (UASB) reactors. Because of its flocculent nature, start-up with digested sludge instead of granular sludge proceeds much slower and presents various operational problems. Any manner in which the granulation of digested sludge can be enhanced would benefit UASB reactor start-up and application in developing countries such as South Africa. The main objective of this dissertation was to improve granulation and reduce UASB reactor start-up by using pre-treated digested sludge as seed. The sludge was pre-treated based on the batch granulation-enhancement model of Britz et al. (2002). The main aim of the model was to improve extracellular polymer (ECP) production of lactate-utilising populations by applying short-term controlled organic overloading in a mechanically agitated environment. The batch granulation-enhancement (pre-treatment) process was applied to an ECP-producing digester strain, Propionibacterium jensenii S1. Non-methanogenic aggregates were formed when batch units were incubated on a roller-table instead of a linear-shake platform. Larger, more stable aggregates were obtained in the presence of apricot effluent medium. Preliminary batch granulation-enhancement studies confirmed that using the roller-table as mixing system had a positive influence on batch granulation-enhancement. The roller-table showed the most potential for handling larger volumes in comparison to a linear-shake waterbath and linear-shake platform. The addition of 450 mg.L-1 Fe2+ at the start of the study also influenced aggregate numbers positively. These studies revealed that pre-treatment results varied depending on the seed sludge source. A denaturing gradient gel electrophoresis (DGGE) method was applied for the detection of Archaea in digested sludges and UASB granules. In addition, a methanogenic marker containing methanogens important to the granulation process was constructed to aid identification. The positive influence of DMSO and “touchdown” PCR on the elimination of artifactual double bands in DGGE fingerprints were also demonstrated. Results revealed that only one of the four digested sludges tested contained Methanosaeta concilii (critical to granular nuclei formation) while it was present in all the UASB granules regardless of substrate type. Four digested sludges were obtained from stable secondary digesters. DGGE indicated the presence of M. concilii in all sludges. The Athlone 4Sb-sludge was the only sludge which exhibited measurable methanogenic activity during substrate dependent activity testing. The ST-sludge showed the highest increase in volatile suspended solids (VSS) particles ≥0.25 mm2. Laboratory-scale UASB reactor start-up was done with both sludges and start-up proceeded better in the Athlone 4Sb-reactor. Athlone 4Sb-sludge batches were pre-treated in a rolling-batch reactor in the presence of either lactate or sucrose and used to seed lab-scale UASB reactors B (sucrose seed) and C (lactate seed). Start-up efficiencies were compared to a control (Reactor A). Overall Reactor B was more efficient that the control. At the end of the study the Reactor B sludge had a higher methanogenic activity than the control reactor. It also had the highest increase in VSS ≥1.0 mm2. Pre-treatment of digested sludge in the presence of sucrose, therefore, aided granulation and reduced UASB reactor start-up time.

The master´s thesis deals with the problem of sewage sludge from wastewater treatment plants and their subsequent incineration. Main aim is compare some possibilities of the energy use of mechanically dewatered sewage sludge and sewage sludge with previous anaerobic pre-treatment for various levels of drying sludge.

Ecosystem restoration, and satisfactory revegetation of strip-mined areas provides an amiable complement to the disposal of treated sewage sludge. Although surface mining is often the most economical method for removing mineral resources, its detrimental impacts on the land surface landscape and ecological environment is and will continue to be a concern. The problem of reclaiming lands disturbed by mining activities is extremely important, as is the sustainability of these reclaimed lands. Stringent regulations, in combination with aie cost of commercial fertilizers, make the search for fertilizer substitutes and alternate soil amendments vital. The use of anaerobically digested de-watered sewage sludge as both a fertilizer source and a soil organic matter amendment in mine reclamation can provide the solution to two pressing and use-related problems: the disposal of treated sewage sludge in a beneficial re-use function and the reclamation and revegetation of mine spoils. Sewage sludges can be regarded as a recyclable source of nutrients and organic matter, and can aid in revegetation and initiation of a sustainable soil humus complex. The purpose of this symposium submission is to review the current state of knowledge on the use of sewage sludges for revegetation and reclamation of surface/strip mines and mine spoils. The long-term sustainability of reclamation efforts utilizing sludges will be detailed by assessing related research projects and operational trials. Results of a joint GVRD/UBC investigation of the use of sewage sludge as an organic forest fertilizer will be presented. Potential environmental impacts are reviewed including effects on vegetation, soil properties, water quality and animal health.