Sequencing batch reactor (SBR) systems were used for the development of a system and operating procedures for the high production of polyhydroxyalkanoates (PHAs) by wastewater treatment (activated sludge) bacterial cultures. It was found that unbalanced growth conditions stimulated massive PHA production in activated sludge biomass. Operating conditions had a significant effect on PHA production and the composition of the accumulated copolymer when either laboratory prepared mixtures of organics or a high acetic acid industrial wastewater were used as the organic substrate mixture. Fully aerobic (AE) conditions with nitrogen (N) and phosphorus (P) limitations were the optimum conditions for PHA production when the laboratory prepared mixtures of orgnics were used, while fully AE with the combinations of N, P, and potassium (K) limitations were better for PHA production using a high acetic acid industrial wastewater as the substrate. One nutrient limitation or partial limitation of either N or P as used for commercial production using pure cultures did not promote massive PHA production in activated sludge biomass compared to the combination of nutrient limitations. A maximum cellular PHA accumulation of 70%TSS was obtained under fully AE conditions with multiple alternating periods of growth and N&P limitations. Microaerophilic/aerobic (MAA/AE) or anaerobic/aerobic (AN/AE) cycling promoted less PHA production compared to fully AE conditions. The relative amounts of the PHA copolymers formed, i.e., polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) were different under different operating conditions, even though the types and amounts of volatile fatty acids (VFAs) in the feed were the same. It was determined that high total phosphorus (TP) content inside the bacterial cells had a significant detrimental impact on PHA production by activated sludge biomass. A two-stage bioprocess was a better approach for obtaining activated sludge PHA accumulation because a growth phase was necessary to grow the bacterial population that contains minimal TP before starting the subsequent PHA accumulation phase. Seeding sludge obtained from a conventional fully aerobic wastewater treatment system was more suitable than seed obtained from a biological phosphorus removal (BPR) system because bacterial populations from BPR systems tended to convert organic substrates to intracellular carbohydrate content rather than PHA under nutrient limitation conditions. The molecular weights and melting point temperatures of PHAs produced by the mixed culture of activated sludge biomass were comparable to those obtained from pure cultures and have the potential to be used for commercial applications. The results of this study indicate that activated sludge biomass has considerable potential for PHA production for commercial purposes, and likely could do so utilizing wastewater sources of organics. In particular organic rich, nutrient limited wastewaters have potential for efficient PHA production. / Ph. D.

Digitized by Kansas Correctional Industries

The specific research work described in this thesis forms part of a much larger research project that was funded by the Technology Programme of the UK Government. This larger project considered improving the design and efficiency of membrane bioreactor (MBR) plant by using modelling, simulation and laboratory methods. This research work uses phenomenological mechanistic models based on MBR filtration and biochemical processes to measure the effectiveness of alternative behavioural models based upon input-output system identification methods. Both model types are calibrated and validated using similar plant layouts and data sets derived for this purpose. Results prove that although both approaches have their advantages, they also have specific disadvantages as well. In conclusion, the MBR plant designer and/or operator who wishes to use good quality, calibrated models to gain a better understanding of their process, should carefully consider which model type is selected based upon on what their initial modelling objectives are (e.g. using either a physically mechanistic model or an input-output behaviourial model). Each situation usually proves unique. In this regard, this research work creates a "Model Conceptualisation Procedure" for a typical MBR which can be used by future researchers as a theoretical framework which underpins any newly created model type. There has been insufficient work completed to date on using a times series input-output approach in the model development of a wastewater treatment plant, so only general conclusions can be made from this research work. However, it can be stated that this novel approach seems to be applicable for a membrane filtration model if care it taken to select appropriate input-output model structures, such as those suggested in the "Model Conceptualisation Procedure". In the case of the development of a MBR biological model, it is thought that a conventional Activated Sludge model produced by the IWA could be coupled to a input-output model structure as suggested by this report to give a hybrid model structure that may have the advantages of both model types. Further research work is needed in this area. Future work that should follow on from this research study should focus on whether these input-output models could be used for predictive control purposes, whether an integrated model could be created, and whether a benchmark could be created for the three main MBR configurations.

O principal impacto ambiental do processo de beneficiamento da casca de coco verde é a geração de resíduo líquido com elevada carga orgânica. Este trabalho teve como objetivo aplicar o sistema convencional de lodos ativados para o tratamento biológico do líquido gerado no beneficiamento da casca de coco verde, além de utilizar o teste de taxa de consumo de oxigênio (TCO) para avaliar a toxicidade do efluente ao lodo aeróbio. O reator de escala laboratorial foi inoculado com lodo proveniente de uma estação de tratamento de esgoto em escala plena. Inicialmente o sistema foi alimentado com efluente sintético contendo sacarose e nutrientes para posterior adição progressiva do resíduo líquido proveniente da reciclagem da casca de coco verde. Para o ensaio de respirometria, as composições testadas foram 25, 50, 75 e 100% de resíduo líquido em termos de carga orgânica e o teste se baseou na medição manual da TCO ao longo do tempo. Para cada composição de efluente se verificou o valor máximo de TCO, o nível de toxicidade devido ao líquido da casca de coco verde (LCCV) e a indicação de inibição permanente. O parâmetro usado nos cálculos de toxicidade e de inibição permanente foi a taxa de consumo de oxigênio específica (TCOe) máxima. Para o monitoramento do sistema de fluxo contínuo, foram empregados os parâmetros pH, índice volumétrico de lodo (IVL), oxigênio dissolvido (OD), demanda química de oxigênio (DQO), taninos totais e sólidos suspensos. O reator foi operado com carga orgânica volumétrica (COV) de 0,8 a 2,9 gDQO/L.d e tempo de detenção hidráulica (TDH) de 26,7 d. Devido à presença natural de leveduras no resíduo líquido, os testes de respirometria foram realizados com o efluente tanto esterilizado quanto in natura. Como os resultados preliminares de respirometria não foram conclusivos, optou-se por começar a adaptação do reator de fluxo contínuo com a menor porcentagem testada: 25% de resíduo líquido. Nos testes adicionais de respirometria não houve toxicidade ao lodo e a TCOe foi diretamente proporcional à concentração de resíduo líquido. A remoção média de DQO obtida durante a operação (LCCV a 100%) foi de 81% com amostra filtrada e 82% com amostra bruta. Houve diminuição significativa da concentração de taninos, de 5332 para 1206 mg/L, em média. No início da operação ocorreu o decaimento da concentração de oxigênio dissolvido (OD) no reator para valores menores que 1 mg/L em decorrência do aumento da concentração de biomassa, mas esta situação não afetou a remoção de matéria orgânica e nem a sedimentabilidade do lodo. A remoção de matéria orgânica obtida com o tratamento em escala laboratorial do LCCV mostra que o sistema convencional de lodos ativados pode ser aplicado como alternativa no tratamento biológico dos resíduos líquidos do beneficiamento da casca de coco verde, porém a demanda elevada de oxigênio pode ser um entrave na operação em escala plena. / The main disadvantage of coconut recycling is the highly pollutant wastewater generated during the process. The objectives of this study were to treat the coconut husk liquor (CHL) using a conventional activated sludge system (AS) and to use the oxygen uptake rate (OUR) test for determining the initial effluent composition of reactor feeding and for wastewater toxicity assessment. The laboratory-scale reactor was inoculated with sludge from a full-scale sewage treatment plant. Firtly the system was fed with synthetic effluent containing saccarose and nutrients which was substituted by CHL. For the OUR test the substrate compositions were 25, 50, 75 and 100% of CHL. For each substrate composition, it was verified the maximum OUR value, the toxicity level and permanent inhibition caused by CHL. The maximal specific oxygen uptake rate (SOUR) was the parameter applied for the toxicity assessment and permanent inhibition calculation. The lab-scale reactor was monitored on the basis of pH, sludge volume index, dissolved oxygen, chemical oxygen demand (COD), total tannins and suspended solids. The respirometry assays were carried out with sterilized and natural effluent because of yeast contamination in CRW. Because of the lack of conclusive results in the first respirometry test, it was chosen the lower composition for reactor adaptation beginning: CRW 25%. In the additional OUR tests it was not detected toxicity and the SOUR values were as higher as CRW concentration. After initializing the reactor adaptation with CRW 25%, the percentage changed to 30% and than increased by 10% each 2 or 3 days until the operation beginning. The mean COD removal values were 81% (filtered sample) and 82% (raw sample). The mean tannin concentration decreased from 5332 to 1206 mg/L. The organic removal and sludge settleability were not affected by the DO concentration decrease to less than 1 mg/L due to biomass increase. The organic removal obtained in the lab-scale AS treatment shows that this system can be an alternative for CHL biological treatment, even though the high oxygen demand could be a disadvantage at full-scale treatment.

Typescript, etc. / Digitized by Kansas Correctional Industries

Digitized by Kansas Correctional Industries

O principal impacto ambiental do processo de beneficiamento da casca de coco verde é a geração de resíduo líquido com elevada carga orgânica. Este trabalho teve como objetivo aplicar o sistema convencional de lodos ativados para o tratamento biológico do líquido gerado no beneficiamento da casca de coco verde, além de utilizar o teste de taxa de consumo de oxigênio (TCO) para avaliar a toxicidade do efluente ao lodo aeróbio. O reator de escala laboratorial foi inoculado com lodo proveniente de uma estação de tratamento de esgoto em escala plena. Inicialmente o sistema foi alimentado com efluente sintético contendo sacarose e nutrientes para posterior adição progressiva do resíduo líquido proveniente da reciclagem da casca de coco verde. Para o ensaio de respirometria, as composições testadas foram 25, 50, 75 e 100% de resíduo líquido em termos de carga orgânica e o teste se baseou na medição manual da TCO ao longo do tempo. Para cada composição de efluente se verificou o valor máximo de TCO, o nível de toxicidade devido ao líquido da casca de coco verde (LCCV) e a indicação de inibição permanente. O parâmetro usado nos cálculos de toxicidade e de inibição permanente foi a taxa de consumo de oxigênio específica (TCOe) máxima. Para o monitoramento do sistema de fluxo contínuo, foram empregados os parâmetros pH, índice volumétrico de lodo (IVL), oxigênio dissolvido (OD), demanda química de oxigênio (DQO), taninos totais e sólidos suspensos. O reator foi operado com carga orgânica volumétrica (COV) de 0,8 a 2,9 gDQO/L.d e tempo de detenção hidráulica (TDH) de 26,7 d. Devido à presença natural de leveduras no resíduo líquido, os testes de respirometria foram realizados com o efluente tanto esterilizado quanto in natura. Como os resultados preliminares de respirometria não foram conclusivos, optou-se por começar a adaptação do reator de fluxo contínuo com a menor porcentagem testada: 25% de resíduo líquido. Nos testes adicionais de respirometria não houve toxicidade ao lodo e a TCOe foi diretamente proporcional à concentração de resíduo líquido. A remoção média de DQO obtida durante a operação (LCCV a 100%) foi de 81% com amostra filtrada e 82% com amostra bruta. Houve diminuição significativa da concentração de taninos, de 5332 para 1206 mg/L, em média. No início da operação ocorreu o decaimento da concentração de oxigênio dissolvido (OD) no reator para valores menores que 1 mg/L em decorrência do aumento da concentração de biomassa, mas esta situação não afetou a remoção de matéria orgânica e nem a sedimentabilidade do lodo. A remoção de matéria orgânica obtida com o tratamento em escala laboratorial do LCCV mostra que o sistema convencional de lodos ativados pode ser aplicado como alternativa no tratamento biológico dos resíduos líquidos do beneficiamento da casca de coco verde, porém a demanda elevada de oxigênio pode ser um entrave na operação em escala plena. / The main disadvantage of coconut recycling is the highly pollutant wastewater generated during the process. The objectives of this study were to treat the coconut husk liquor (CHL) using a conventional activated sludge system (AS) and to use the oxygen uptake rate (OUR) test for determining the initial effluent composition of reactor feeding and for wastewater toxicity assessment. The laboratory-scale reactor was inoculated with sludge from a full-scale sewage treatment plant. Firtly the system was fed with synthetic effluent containing saccarose and nutrients which was substituted by CHL. For the OUR test the substrate compositions were 25, 50, 75 and 100% of CHL. For each substrate composition, it was verified the maximum OUR value, the toxicity level and permanent inhibition caused by CHL. The maximal specific oxygen uptake rate (SOUR) was the parameter applied for the toxicity assessment and permanent inhibition calculation. The lab-scale reactor was monitored on the basis of pH, sludge volume index, dissolved oxygen, chemical oxygen demand (COD), total tannins and suspended solids. The respirometry assays were carried out with sterilized and natural effluent because of yeast contamination in CRW. Because of the lack of conclusive results in the first respirometry test, it was chosen the lower composition for reactor adaptation beginning: CRW 25%. In the additional OUR tests it was not detected toxicity and the SOUR values were as higher as CRW concentration. After initializing the reactor adaptation with CRW 25%, the percentage changed to 30% and than increased by 10% each 2 or 3 days until the operation beginning. The mean COD removal values were 81% (filtered sample) and 82% (raw sample). The mean tannin concentration decreased from 5332 to 1206 mg/L. The organic removal and sludge settleability were not affected by the DO concentration decrease to less than 1 mg/L due to biomass increase. The organic removal obtained in the lab-scale AS treatment shows that this system can be an alternative for CHL biological treatment, even though the high oxygen demand could be a disadvantage at full-scale treatment.

No description available.

With water scarcity as a pressing issue in Saudi Arabia and other Middle Eastern countries, the treatment and reuse of municipal wastewater is increasingly being used as an alternative water source to supplement country water needs. Standards are in place to ensure a safe treated wastewater quality, however they do not regulate pathogenic bacteria and emerging contaminants. Information is lacking on the levels of risk to public health associated with these factors, the efficiency of conventional treatment strategies in removing them, and on wastewater treatment in Saudi Arabia in general. In this study, a municipal wastewater treatment plant in Saudi Arabia is investigated to assess the efficiency of conventional treatment in meeting regulations and removing pathogens and emerging contaminants. The study found pathogenic bacterial genera, antibiotic resistance genes and antibiotic resistant bacteria, many of which were multi-resistant in plant discharges. It was found that although the treatments are able to meet traditional quality guidelines, there remains a risk from the discussed contaminants with wastewater reuse. A deeper understanding of this risk, and suggestions for more thorough guidelines and monitoring are needed.

Pretreatment of waste activated sludge (WAS) and the subsequent near-critical water gasification (NCWG) is a potential avenue to convert WAS into value added products. Part one of the research investigated thermal and thermochemical pretreatments. No difference was observed in the percentage of sludge liquefied beyond 10min between 200°C to 300°C. It was found that pretreated activated sludge supernatant (PASS) doubled the gas yield compared to untreated sludge when gasified. The order of effectiveness for sludge treatment was thermo-alkali > thermal > thermo-acid for hydrogen production in NCWG. Part two investigated NCWG parameters to identify optimal conditions. High gasification yields were obtained using a commercial catalyst (Raney nickel), with hydrogen content of 65-75% of the gas phase products. Thermo-alkali treated PASS was found to perform well at subcritical temperatures with 25% higher yields than thermally treated PASS. Increased catalyst loading had little additional effect on gas yields above 0.075g.