Academic literature on the topic 'Continuous-flow biological treatment'

This paper analyses the steady-state operation of a generalized bioreactor model that encompasses a continuous-flow bioreactor and an idealized continuous-flow membrane bioreactor as limiting cases. A biodegradation of organic materials is modelled using Contois growth kinetics. The bioreactor performance is analysed by finding the steady-state solutions of the model and determining their stability as a function of the dimensionless residence time. We show that an effective recycle parameter improves the performance of the bioreactor at moderate values of the dimensionless residence time. However, at sufficiently large values of the dimensionless residence time, the performance of the bioreactor is independent of the recycle ratio.

A continuous flow double chamber microbial fuel cell (MFC) for wastewater treatment was constructed. Anaerobic activated sludge was used as bacterial source and simulated organic wastewater was used as substrate. Effluent of anode chamber was used directly as influent of the cathode chamber. The aerobic microorganisms could degrade organic matters further. The electricity production and organic wastewater treatment of the MFC were studied. The results show that the wastewater chemical oxygen demand (COD) of the total removal rate was 74.1%~77.45%, the anode chamber in which the removal rate of COD is 32.2%~35.3%, and COD removal efficiency of aerobic biological treatment in the cathode chamber was 60.2%~66.7%. The continuous flow system could improve the removal rate further. The maximum current density of MFC was 1.56 mAm-2, the maximum output power was 24.336 mWm-2.

Increasing the efficiency and capacity of existing wastewater treatment plants can be carried out by using intensive biological processes. One of the currently studied biological solutions consists in using aerobic granular sludge in order to achieve both organics and nutrients removal simultaneously in one tank and with high efficiency. Aerobic granular sludge is currently used at full scale in sequential batch reactors, research for identifying the optimal solutions for continuous flow systems being carried out worldwide. The paper summarizes the results obtained for two continuous flow configurations with aerobic granular sludge, in terms of organics and nutrients removal for synthetic wastewater in laboratory conditions. Both experimental setups led to wastewater treatment efficiencies, with values ranging between 80 and 99% for COD, 85 and 99% for BOD5, 52 and 98% for NH4+ and 5 to 87% for TP.

The focus of this study was to assess the treatment performance and granule progression over time within a continuous flow reactor. A continuous flow airlift reactor was seeded with aerobic granules from a laboratory scale sequencing batch reactor (SBR) and fed with dairy wastewater. Stereomicroscopic investigations showed that the granules maintained their integrity during the experimental period. Laser diffraction investigation showed proof of new granules formation with 100–500 μm diameter after only 2 weeks of operation. The treatment performances were satisfactory and more or less similar to the ones obtained from the SBR. Thus, removal efficiencies of 81–93% and 85–94% were observed for chemical oxygen demand and biological oxygen demand, respectively. The N-NH+4 was nitrified with removal efficiencies of 83–99% while the nitrate produced was simultaneously denitrified – highest nitrate concentration determined in the effluent was 4.2 mg/L. The removal efficiency of total nitrogen was between 52 and 80% depending on influent nitrogen load (39.3–76.2 mg/L). Phosphate removal efficiencies ranged between 65 and above 99% depending on the influent phosphate concentration, which varied between 11.2 and 28.3 mg/L.

This study examines the effect of powdered activated carbon (PAC) addition to activated sludge in the treatment of pulp bleaching effluents which contain a large amount of nonbiodegradable matter. The effect of PAC addition has been studied in both batch and continuous-flow reactors. Isotherms were developed for PAC and biomass adsorption. It was shown that substrate removal by air stripping and biosorption was negligible. The change in substrate concentration occurred mainly by biodegradation. The biological removal data obtained in batch and continuous-flow reactors were fitted to kinetic models. Both batch and continuous-flow experiments revealed that there remained a high amount of nonbiodegradable substrate as expressed by residual COD and Color436. Carbon addition to activated sludge resulted in a high decrease in substrate concentration, particularly for color. However, the results indicated that there was no noticable biological enhancement with PAC addition. The combined PAC and activated sludge process seemed to be a combination of adsorption and biodegradation.

A program of batch, continuous-flow, and field pilot tests have been conducted to measure the extent and stability of nitrification in kraft wastewater. Laboratory batch tests measured the extent and rate of ammonia removal from kraft wastewater. Controlled variables included aerated stabilization basin (ASB) location, temperature, pH, ammonia concentration, black liquor content, bicarbonate content, and presence of acclimated nitrifying bacteria. Findings were that (a) moderate wastewater temperature (22-35°C), pH near 7.3, and black liquor spill control prevented slowing of nitrification, and (b) provision of acclimated nitrifying bacteria (by appropriate recirculation methods) dramatically reduced the residence time needed for nitrification in kraft ASBs. Laboratory-scale, fixed-film, continuous-flow tests were used to investigate dynamic responses to changes in wastewater composition and flow. Results demonstrated that the nitrifying films were not ‘damaged’ by 4- or 24-hour step increases in influent ammonia, but the films could not respond quickly enough to substantially dampen out the effect on effluent quality. A pilot 4-stage rotating biological contactor (RBC) was installed at an ASB to test the nitrification of kraft wastewater under actual process variations. The results during the 11-month run were: (a) the RBC demonstrated capability to consistently and substantially reduce NH4-N concentration below 1 mg/L, (b) about one month was needed to establish effective treatment, and (c) effective treatment was sustained at a maximum hydraulic loading rate of 0.11 m3/day per m2.

Aerobic biological treatment of digested sludge was studied in a continuously operated laboratory set-up. An aerated reactor was filled with thermophilically digested sludge from the Moscow wastewater treatment plant and inoculated with special activated sludge. It was then operated at the chemostat mode at different flow rates. Processes of nitrification and denitrification, as well as dephosphatation, occurred simultaneously during biological aerobic treatment of thermophilically digested sludge. Under optimal conditions, organic matter degradation was 9.6%, the concentrations of ammonium nitrogen and phosphate decreased by 89 and 83%, respectively, while COD decreased by 12%. Dewaterability of digested sludge improved significantly. The processes were found to depend on hydraulic retention time, oxygen regime, and temperature. The optimal conditions were as follows: hydraulic retention time 3–4 days, temperature 30–35 °C, dissolved oxygen levels 0.2–0.5 mg/L at continuous aeration or 0.7–1 mg/L at intermittent aeration. Based on these findings, we propose a new combined technology of wastewater sludge treatment. The technology combines two stages: anaerobic digestion followed by aerobic biological treatment of digested sludge. The proposed technology makes it possible to degrade the sludge with conversion of ∼45% volatile suspended solids to biogas, to improve nitrogen and phosphorus removal in reject water from sludge treatment units, and to achieve removal of malodorous substances after 8–9 days of anaerobic–aerobic sludge treatment.

Many municipalities and industrial plants with small quantities of wastewater are facing challenges with providing economical treatment strategies. They require simply designed and operated processes which give high quality effluent. One such process is the Intermittent Cycle Extended Aeration System (ICEAS R). This is a variant of the activated sludge biological process which allows continuous inflow of raw wastewater and intermittently discharged influent. It provides flow equalization, biological oxidation and sedimentation with decanting of supernatant in a single tank. The process can be operated on any cycle duration based on the required degree of treatment. Each cycle consists of aeration, sedimentation and decantation phases. The aeration phase can be operated on an oxic/anoxic mode for the purpose of nitrification/denitrification and biological phosphorus removal. To date, there are more than 100 plants worldwide and 25 within the U.S.A. that are built and operating successfully. High degrees of BOD, suspended solids and nitrogen removal are obtained with the plants. Most of the small plants require minimal operating personnel, generally one or two, for continuous operation.

Användandet av deponier är en av de vanligaste metoderna för avfallshantering globalt. Trots insatser som gjordes för att förbjuda hushållsavfall i deponier under millennieskiftet, deponier skapade innan restriktionerna är fortfarande en risk för miljön. Under 2014 öppnade SÖRAB en kontinuerlig biologisk reningsanläggning (KBR-anläggning) på Löt Avfallsanläggning för att hantera lakvatten från en gammal deponi som under en tid fylldes med hushållsavfall. Sedan dess har SÖRAB arbetat med att förbättra KBR-anläggningen. Målet med denna studie är att utforma en driftstrategi för KBR-anläggningen för att förbättra kvävereningen vid låga temperaturer. Ett antal laborativa försök genomfördes, såsom den mikrobiella konsortiets livsduglighet i lakvattnet och tillväxten i både rumstemperatur och vid 4°C, bioaugmentation genom att berika den mikrobiella cellkulturen som redan finns i lakvattnet och hur detta förbättrar kvävereningen i jämförelse med tillsatser av den kommersiella bakterieblandningen ClearBlu Environmental och andra externa kolkällor. Resultaten från dessa laborativa försök påvisade komplett nitrifikation i både rumstemperatur och 4°C i berikat lakvatten från KBR-anläggningens L2A bassäng efter fem dagar. Försöket visade även på syresatt denitrifikation. Dessutom påvisades komplett denitrifikation inom fem dagar, vid rumstemperatur i lakvatten från anläggningens L2B bassäng. Under efterföljande pilotförsök påvisades möjligheten till upplivandet av den biologiska kvävereningen genom berikningen av den mikrobiella cellkulturen i lakvattnet. I ett pilotförsök då lakvatten från L2B bassängen berikades, komplett denitrifikation skedde under en anaerob fas på 16 dagar samt nitrifikation och aerob denitrifikation under ett påföljande 17 dagar lång aerob fas. Ett annat pilotförsök då lakvatten från L2A bassängen berikades påvisade både aerob och anaerob nitrifikation, då ammoniumrening skedde i både den syresatta och syrefria fasen. Tillsatsen av nutrient broth (näringsbuljong) kan påverka KBR-anläggningen, vilket kväver vidare studier. Resultatet från detta projekt tydligt påvisar att kvävereningen i KBR-anläggningen kan förbättras genom att berika den redan närvarande mikrobiella kulturen.
Landfilling has been one of the most popular methods of handling waste globally. Despite the efforts made to stop the disposal of household waste during the turn of the millennia, the landfills formed before these restrictions are still at risk for causing harm to the environment. In 2014, SÖRAB opened a continuous-flow biological treatment (KBR) facility in Löt to treat the leachate produced in one of their older landfills, once filled with household waste. Since then, SÖRAB has been working on improving the treatment facility. The aim of this the study is to find a suitable process to enhance the nitrogen removal at low temperature. Several laboratory scale experiments were performed, such as viability of microbial consortia in the leachate and growth at room temperature and at 4°C, testing bioaugmentation by enriching the microbial cell culture in the leachate and their efficiency in removing nitrogen, compared to the commercial cell culture ClearBlu Environmental and carbon source addition. The results displayed complete nitrification at both room temperature and 4°C in bioaugmented, enriched leachate originating from the L2A basin of the KBR facility, after five days. These trials also suggested the occurrence of aerated denitrification. Complete denitrification within five days was seen at room temperature in bioaugmented, enriched leachate from the L2B basin of the same facility. The ensuing pilot scale trials proved the possibility to revive the biological nitrogen removal by microbial cell culture enrichment. In one pilot in which leachate from the L2B basin was enriched, complete denitrification in the anaerobic phase consisting of 16 days occurred, along with some nitrification and aerated denitrification in the 17 day long aerated phase that followed. Another pilot scale trail in which leachate from the L2A basin was enriched, both aerobic and anaerobic nitrification occurred, as ammonium removal occurred in both the aerated and unaerated phases. The addition of nutrient broth might influence the KBR system which needs further study. The results from this project clearly demonstrate that nitrogen removal in the KBR facility could be enhanced using a culture naturally present in the facility.

The objective of this study was to examine excess biological phosphorus removing bacterial populations and their substrate utilization mechanisms. This study was a smaller part of a overall study of temperature effects upon excess biological phosphorus removal. Bacterial populations in both a continuous flow UCT (University of Cape Town) system and batch reactors were examined by direct counting using a well known staining procedure (Neisser staining), and a microscopic counting method developed by Cech and Hartman (1993). Substrate utilization was examined using PHB (Poly-β -Hydroxybutyrate - an internal substrate storage product) analysis by gas chromatography to supplement COD and acetate measurements. The results showed that Poly-P bacterial counts were significantly greater at a 5 day sludge age compared to a 10 day sludge age. It was noted from microscopic observations that the size of the poly-phosphate granules in the bacteria seemed to be a better indicator of system performance than the actual counts. It also was observed that the 'G' bacteria first described by Cech and Hartman (1993) were abundant at the 10 day sludge age but completely absent at the 5 day sludge age. PHB storage occurred in both the anaerobic zone and the first aerobic tank, and PHB utilization was seen in the subsequent aerobic tanks of the UCT system. The formation of PHB in the first aerobic reactor when no substrate was available supports the Mino (1987) model for excess biological phosphorus removal. In batch studies, substrate storage release were demonstrated in the aerobic zone. This explained why when acetate was present in the aerobic zone net phosphorus uptake didn't occur until all the acetate was utilized. When the temperature was lowered in the UCT system nitrification ceased. This resulted in soluble COD breakthrough into the aerobic zone, which stimulated filamentous growth, and eventually caused a lack of PHB formation. All of these factors contributed to a loss of excess biological phosphorus removal at the low temperature.
Master of Science

Dissertação de Mestrado Integrado em Engenharia do Ambiente apresentada à Faculdade de Ciências e Tecnologia
O Reator de Biofilme com Leito Móvel, mais conhecido como MBBR (Moving Bed Biofim Reactor em inglês) e o Reator Integrado de Lamas Ativadas com Biofilme em Leito Móvel, ou IFAS (Integraded Fixed-Film Activated Sludge em inglês) são sistemas biológicos avançados para o tratamento de águas residuais. As vantagens associadas às suas aplicações contribuíram para que muitos cientistas realizassem estudos sobre esses sistemas, uma vez que proporcionam uma operação mais fácil, com elevadas eficiências de remoção de carga orgânica para além de produzirem menos quantidade de lama, sendo uma vantagem a nível económico muito grande pois o despejo das lamas corresponde à maioria dos custos de operação, quando comparados com o sistema de Lamas Ativadas. O IFAS consegue ser facilmente implementado numa estação de tratamento de água que já utilize o sistema LA, sem que sejam necessários custos associados à ampliação do sistema. O MBBR tem como grande vantagem o facto de não necessitar de um sistema de recirculação de lamas.O presente trabalho teve como objetivo a comparação de três reatores, LA, IFAS e o MBBR em termos de eficiência de tratamento, caracterização da biomassa e identificação microbiológica. O sistema experimental consistiu em três reatores independentes que operaram em modo continuo ao longo da experiência. O efluente utilizado foi composto por uma diluição de leite com água, de modo a assemelhar-se o mais possível com um efluente proveniente de uma indústria de lacticínios real. A experiência foi dividida em dois períodos, A e B. Em ambos os períodos foram utilizados as mesmas frações de enchimento, 44.5% no reator MBBR e no reator IFAS. O período A, durou 37 dias e utilizou-se uma diluição de 1:200, já o período B teve uma duração de 25 dias e a diluição passou a ser de 1:100. Com a variação da quantidade de carga orgânica a entrar em cada um dos reatores, foi possível obter os desempenhos e relacionar cada um, face ao aumento da carga orgânica, bem como a variação do consórcio de microrganismos. O IFAS mostrou melhor desempenho, nos parâmetros analisados, em ambos os períodos face ao MBBR e ao LA. As eficiências de remoção de Carência Química de Oxigénio (CQO) no período A foram de 63%, 73% e 71% para LA, IFAS e MBBR respetivamente. O período B obteve melhores eficiências de remoção para os parâmetros analisados, com a exceção do MBBR, que no segundo dia, após o início experiência, sofreu um washout que levou à saída das lamas de dentro do reator para o tanque do efluente tratado, e subsequentemente o biofilme sofreu o fenómeno de dettachement, que fez com que grande parte do biofilme fosse perdido. O aumento da carga orgânica e problemas associados aos difusores de ar podem justificar o problema. As eficiências de remoção do CQO foram 82%, 84% e 79% para o LA, IFAS e MBBR, respetivamente. Durante o período B, o IFAS produziu menos 36.5% de lamas que o LA, enquanto que o MBBR produziu menos 85.5%. Para a caracterização microbiológica, foi utilizada como amostra, a biomassa suspensa. Conclui-se, que durante os períodos analisados não houve indícios de zoogleal bulking ou de filamentous bulking, mas, no entanto, surgiram indícios de pinpoint no reator MBBR, que foram justificados através da caracterização da biomassa e da própria observação microbiológica, uma vez que tanto a quantidade de microrganismos e de biomassa presentes no licor misto diminuíram drasticamente. Os mesoflocos predominaram nos três reatores em ambos os períodos, sendo esses associados a boas condições de sedimentação. As análises dos parâmetros morfológicos da biomassa, em ambos os períodos, permitiu concluir que os flocos de menores dimensões têm uma estrutura menos alongada, são mais densos e têm fronteiras mais suaves, enquanto que os flocos de maiores dimensões têm uma forma mais alongada, são menos densos e as suas fronteiras são mais ásperas. Conclui-se também que os ciliados foram o grupo de protozoários dominante, durante o decorrer da experiência, principalmente no IFAS. Por outro lado, foi possível observar que o reator LA tinha maior concentração de metazoários quando comparado com o MBBR e o IFAS. O MBBR foi o sistema com menor concentração de microrganismos, tendo sido observado ciliados e alguns metazoários de menores dimensões, foi detetado no final do período A, a espécie tardígrados, que está associada a idades de lamas avançadas. As espécies mais comuns de ciliados foram Colpidium sp, Zoothamnium sp, Vorticella micróstoma sp, Aspidisca cicada e Vorticella convallaria sp, e o principal grupo de metazoários foram os rotíferos em que foi possível principalmente as espécies Digononta e Monogononta.
The Moving Bed Biofilm Reactor, MBBR, and the Integrated Fixed-Film Activated Sludge, IFAS, are advanced biological systems for wastewater treatment. The advantages associated with their applications, contributed to many scientists to carry out many investigations on these systems, as they provide an easier operation, with high organic load removal efficiencies in addition to producing less amount of sludge, being a great economical advantage as the sludge disposal corresponds to the majority of the operations costs, when compared with the Activated Sludge, AS. IFAS system can be easily implemented in water treatment plant, that already uses the AS system, without the need of expansion of the system. The greatest advantages of the MBBR system is that it does not need a sludge recycling system.This study aimed to compare three systems, AS, IFAS and MBBR in terms of treatment efficiency, biomass characterization and microbial identification. The experimental system consisted in three independent reactor that operated in a continuous mode throughout the experiment. The effluent used was composed by a dilution of milk with water, in order to resemble a real dairy effluent. The experiment was divided in two periods, A and B. In both periods the same filling fraction were used, 44.5% for MBBR and IFAS reactors. Period A, lasted 37 days and a dilution of 1:200 was used, whereas period B lasted 25 days and the dilution was 1:100. With the variation in the amount of organic load entering each reactor, it was possible to obtain the performances and relate each one, compared to the organic load increase as well as the variation in the microbial consortium.IFAS showed better performance, in the analysed parameters for both periods compared to MBBR and AS. Chemical Oxygen Demand (COD) removal efficiencies in period A were 63%, 73% e 71% for LA, IFAS and MBBR, respectively. Period B obtained higher efficiencies for the analysed parameters, with the exception of MBBR, which suffered a washout in the second day after the begging of the experiment, that led the sludge out of the reactor, to the treated effluent, and subsequently the loss of biofilm provoked by the detachment phenomena. The increase in the organic load and air diffusers problems may justify the problem. The CQO removal efficiencies were 82%, 84% e 79% for AS, IFAS and MBBR, respectively. During period B, IFAS produced less 36.5 % of sludge than AS, whereas MBBR produced less 85.5%.For biomass characterization, the suspended biomass was used as a sample. It is concluded during the analysed periods, there was no evidence of zoogleal bulking or filamentous bulking, but, nevertheless, there was signs of pinpoint in MBBR reactor, which were justified through the biomass characterization and microbiological observation itself, since the quantity of microorganism and biomass presents in the mixed liquor decreased dramatically. The mesoflocs predominated in the three reactors for both periods, this type of flocs is associated with good settling conditions. The analysis of the morphological parameters, in both periods, allowed to conclude that smaller flocs have a less elongated structure, are denser and have smoother edges, while larger flocs have a more elongated shape, are less dense and have rougher edges. It is also concluded that ciliates were the dominant protozoa group, during the experiment, mainly at IFAS. On the other hand, it eas possible to observe that the AS reactor had a higher concentration of metazoan compared to MBBR and IFAS. MBBR was the system with the lowest microorganism concentration, the ciliates and smaller metazoa was observed, the tardigrade specie was detected at the end of period A which is associated with an advanced sludge age. The most common species of ciliate were, Colpidium sp, Zoothamnium sp, Vorticella micróstoma sp, Aspidisca cicada and Vorticella convallaria sp, and the main group of metazoa were the rotifers in which it was possible to visualize mainly the Digononta sp and Monogononta sp.

Atherosclerosis is a cardiovascular disease that occurs within the walls of arteries and can result in a reduction of the lumen diameter. This reduction can cause a decrease in blood flow to the brain which can lead to a stroke event. Carotid angioplasty stenting (CAS) is a minimally invasive surgical treatment for stroke prevention and has been found to show equivalency to the highly invasive open artery repair which is a more commonly used surgical technique (Brott et al. 2010). Development in the design of stent and angioplasty devices is necessary for the continuous improvement of minimally invasive treatments of carotid artery disease. However, a major concern with regard to this treatment is the rupture of the plaque due to the almost instantaneous inflation of the stent device. To further improve the design of these devices a better understanding of the mechanical behaviour and failure of the plaque during minimally invasive treatment in the circumferential direction is required. A limited amount of data exists regarding the mechanical behaviour of atherosclerotic plaques under physiological conditions. Studies undertaken by Maher et al. (2009) and Teng et al. (2009) have tested the tensile properties of the plaque in the circumferential direction but these studies employed unphysiological strain rates which limit the true representation of the global properties of the plaque. This current study aims to biologically and mechanically characterise the whole plaque tissue and to determine if a correlation exists between the mechanical behaviour and the pre-operatively identified biological content of the plaque.