Este estudo procurou investigar a utilização de polímeros para condicionamento de lodo de ETE para desidratação em filtro prensa de placa e verificar as eventuais vantagens em relação ao condicionamento com cal e cloreto férrico. Para isso foram realizadas pesquisa bibliográfica, consulta a fornecedores de polímeros e de equipamentos e trabalhos experimentais em laboratório e em escala piloto com lodo gerado nos digestores anaeróbios da ETE Barueri da SABESP que mostrava interesse em fazer o condicionamento do lodo com polímeros. Atualmente, na ETE Barueri o condicionamento de lodo é feito com cal e cloreto férrico, com dosagens em torno de 25% e 10% respectivamente e a desidratação em filtro prensa de placas, com tempo de ciclo de 4 horas, produz tortas com 40% de teor de sólidos e densidade de 1,20 kg/L. Nos experimentos foram utilizados polímeros catiônicos de alto peso molecular. O equipamento piloto utilizado foi um filtro prensa de placa do tipo membrana diafragma com dez placas de 800 x 800 mm. Nos ensaios do filtro prensa piloto, com a utilização de polímero em pó para o condicionamento de lodo, indicou-se uma redução nos custos de produtos químicos consumidos em relação ao condicionamento com cal e cloreto férrico. O condicionamento com polímero em pó e cloreto férrico, com dosagens respectivamente de 4,83 kg/ton e 6,3%, resultou numa torta com teor de sólidos de 31% e densidade de 1,13 kg/L. Já o condicionamento feito somente com polímero em pó, com dosagem de 5,38 kg/ton, resultou numa torta com teor de sólidos de 30% e densidade de 1,08 kg/L, porém apresentou problemas na soltura das tortas. A utilização de polímeros permitiu trabalhar em taxas iniciais de filtração mais altas, resultando num tempo de filtração em torno de 120 minutos, implicando em tempos de ciclo mais curtos. / This study investigated the utilization of polymers for the conditioning of the sludge generated at Wastewater Treatment Plants (WTP) for dewatering at filter presses, verifying the eventual advantages in comparison with the conditioning with lime and ferric chloride. Specific bibliography was researched, polymer and equipment suppliers were consulted and experimental studies were carried out at the laboratory and in a pilot scale. The sludge was generated at the anaerobic digesters of Barueri WTP operated by SABESP which has shown interest in this method. Currently, at Barueri WTP the sludge conditioning is performed with lime and ferric chloride at dosages around 25% and 10%, respectively. The dewatering is processed by filter presses during a cycle period of 4 hours, producing cakes with 40% of solids and a density of 1,20 kg/L. The experimental studies were carried out with high molecular weight cationic polymers. The pilot equipment consisted of a filter press with a diaphragm membrane with 10 plates measuring 800 x 800 mm each. During the tests at the pilot filter press, when dry polymers for sludge conditioning were utilized, it was verified that the cost of chemical products consumed was reduced in comparison with the conditioning with lime and ferric chloride. The sludge conditioning with dry polymers and ferric chloride at respective dosages of 4,83 kg/ton and 6,3% resulted in cakes with 31% of solids and density of 1,38 kg/L. On the other hand, the sludge conditioned only with dry polymers at a dosage of 5,38 kg/ton resulted in cakes with 30% of solids and density of 1,08 kg/L, but the cake release from the plates was difficult. The utilization of polymers allowed higher initial filtration rates resulting in a 120 minute filtration period with a consequent reduction of the cycle time.

Este estudo procurou investigar a utilização de polímeros para condicionamento de lodo de ETE para desidratação em filtro prensa de placa e verificar as eventuais vantagens em relação ao condicionamento com cal e cloreto férrico. Para isso foram realizadas pesquisa bibliográfica, consulta a fornecedores de polímeros e de equipamentos e trabalhos experimentais em laboratório e em escala piloto com lodo gerado nos digestores anaeróbios da ETE Barueri da SABESP que mostrava interesse em fazer o condicionamento do lodo com polímeros. Atualmente, na ETE Barueri o condicionamento de lodo é feito com cal e cloreto férrico, com dosagens em torno de 25% e 10% respectivamente e a desidratação em filtro prensa de placas, com tempo de ciclo de 4 horas, produz tortas com 40% de teor de sólidos e densidade de 1,20 kg/L. Nos experimentos foram utilizados polímeros catiônicos de alto peso molecular. O equipamento piloto utilizado foi um filtro prensa de placa do tipo membrana diafragma com dez placas de 800 x 800 mm. Nos ensaios do filtro prensa piloto, com a utilização de polímero em pó para o condicionamento de lodo, indicou-se uma redução nos custos de produtos químicos consumidos em relação ao condicionamento com cal e cloreto férrico. O condicionamento com polímero em pó e cloreto férrico, com dosagens respectivamente de 4,83 kg/ton e 6,3%, resultou numa torta com teor de sólidos de 31% e densidade de 1,13 kg/L. Já o condicionamento feito somente com polímero em pó, com dosagem de 5,38 kg/ton, resultou numa torta com teor de sólidos de 30% e densidade de 1,08 kg/L, porém apresentou problemas na soltura das tortas. A utilização de polímeros permitiu trabalhar em taxas iniciais de filtração mais altas, resultando num tempo de filtração em torno de 120 minutos, implicando em tempos de ciclo mais curtos. / This study investigated the utilization of polymers for the conditioning of the sludge generated at Wastewater Treatment Plants (WTP) for dewatering at filter presses, verifying the eventual advantages in comparison with the conditioning with lime and ferric chloride. Specific bibliography was researched, polymer and equipment suppliers were consulted and experimental studies were carried out at the laboratory and in a pilot scale. The sludge was generated at the anaerobic digesters of Barueri WTP operated by SABESP which has shown interest in this method. Currently, at Barueri WTP the sludge conditioning is performed with lime and ferric chloride at dosages around 25% and 10%, respectively. The dewatering is processed by filter presses during a cycle period of 4 hours, producing cakes with 40% of solids and a density of 1,20 kg/L. The experimental studies were carried out with high molecular weight cationic polymers. The pilot equipment consisted of a filter press with a diaphragm membrane with 10 plates measuring 800 x 800 mm each. During the tests at the pilot filter press, when dry polymers for sludge conditioning were utilized, it was verified that the cost of chemical products consumed was reduced in comparison with the conditioning with lime and ferric chloride. The sludge conditioning with dry polymers and ferric chloride at respective dosages of 4,83 kg/ton and 6,3% resulted in cakes with 31% of solids and density of 1,38 kg/L. On the other hand, the sludge conditioned only with dry polymers at a dosage of 5,38 kg/ton resulted in cakes with 30% of solids and density of 1,08 kg/L, but the cake release from the plates was difficult. The utilization of polymers allowed higher initial filtration rates resulting in a 120 minute filtration period with a consequent reduction of the cycle time.

Wastewater treatment plants (WWTP) involve several complex physical, biological and chemical processes. Often these processes exhibit non-linear behavior that is difficult to describe by classical mathematical models. Safer operation and control of a WWTP can be achieved by developing a modeling tool for predicting the plant performance. In the last decade, many studies were realized in wastewater treatment based on intelligent methods which are related to modeling WWTP. These studies are about predictions of WWTP parameters, process control of WWTP, estimating WWTP output parameters characteristics. In many studies, neural network models were used to model chemical and physical attributes in the flow rate. In this Thesis, a data-driven approach for analyzing water quality is introduced. Improvements in the data collection of information system allow collection of large volumes of data. Although improvements in data collection systems have given researchers sufficient information about various systems, they must be used in conjunction with novel data-mining algorithms to build models and recognize patterns in large data sets. Since the mid 1990's, data mining has been successfully used for model extraction and describing various phenomena of interest.

The project involved the study of 12 Victorian municipal wastewater treatment plant discharges. These included lagoon-based plants and those with activated sludge based processes. Permission was obtained from all the relevant water authorities to collect samples of final effluent at point of discharge to the environment, whether that was to a creek, a river, the ocean, or the land. Samples were collected in November 2003, and then again in April and June 2004, and subjected to a number of biological and chemical analyses, including toxicity tests, measurement of hormonal (estrogenic) activity using yeast-based bioassays, and the measurement of specific hormonal concentrations (17-estradiol) using enzyme-linked immunosorbent assays (ELISA). Almost all of the effluents examined showed estrogenic activity, to a greater or lesser extent (no response to 55 ng/L 17β-estradiol equivalents). On the whole, the levels of estrogenic activity observed were to the lower end of the range observed overseas in the northern hemisphere, and comparable with that recently reported in Australia and New Zealand using similar, human-estrogen receptor based assays (no response to ~ 10 ng/L 17β-estradiol equivalents). The reassuring low/no assay response is bolstered by the chemical assessment of estradiol concentrations by ELISA, which returned concentrations of these compounds for the most part in the range 2-5 ng/L. From an aquatic environmental perspective, it is difficult to say with any certainty what the potential risk to aquatic organisms in waters receiving these effluents will be. Typically, in environmental risk assessment one first looks to agreed national or international guideline or trigger values for the type of waters being assessed. In this case, there are as yet no guideline values. Without guideline values to drive the assessment, then one compares a chemical’s concentration in a sample (in this case a WWTP effluent) with data obtained from toxicological experiments in which the concentration known to elicit a specific effect has been determined. In this case, levels of 17β-estradiol were typically between the lowest reported level to induce the production of Female-indicative proteins in male fish (plasma vitellogen; 1 ng/L), and the lowest concentration of known to induce intersex in fish (8 ng/L). Consequently, such levels in a WWTP discharge are likely to be an environmental risk if there is little or no dilution of the discharge by the receiving water, i.e. discharge represents major component of stream flow. In short, to truly assess the risk (hormonal impact) of these WWTP effluents, in vivo testing needs to be undertaken, ideally with a representative native species but failing that with a ‘standard’ species such as the fathead minnow. When this programme began, the ‘watching brief’, being held in Australia on the topic of endocrine disrupting chemicals and their potential effects on aquatic wildlife was considered too passive by many. It still is, by some. Despite the assurance the results may provide (of minimal impact in most cases if there is significant dilution), there is still a need for further extensive on-ground, reassurance research to provide data for higher-level risk assessment by industry and government agencies.

<p>Hedesunda reningsverk är beläget i södra delen av Gävle kommun och hanterar avloppsvatten från Hedesunda samhälle och ett fåtal närbelägna byar. Antalet anslutna personer är strax över 1500. Reningsverket byggdes på 1960-talet och byggdes om i slutet av 1990-talet. Vid ombyggnaden anlades torkbäddar för avvattning av det slam som produceras vid reningsverket. Inledningsvis fungerade dessa torkbäddar bra men sedan 2005 har slammet i bäddarna inte avvattnats i önskad omfattning.</p><p> </p><p>Syftet med detta examensarbete var att utreda hur slamavvattningen i Hedesunda ska se ut i framtiden. Utgångspunkten var att den nuvarande lösningen är otillräcklig och att en förändring är nödvändig. Inledningsvis delades frågeställningen upp i två separata delar: avvattning av slammet och avsättning för avvattnat slam. Fokus låg på ekonomiska och miljömässiga aspekter av slamhantering och en sammanvägning av dessa gjordes där så var möjligt.</p><p> </p><p>Frågan om hur avvattningen bör se ut undersöktes genom att en enkät skickades ut till nio olika företag som levererar avvattningsutrustning. Dessa fick svara på 17 frågor om vilken lösning de ansåg vara bäst lämpad för reningsverket i Hedesunda. Sammanlagt samlades sex olika svar in. Utöver dessa undersöktes även alternativet att restaurera de befintliga torkbäddarna närmare. Detta skedde bland annat genom provtagning och analys av slammet i bäddarna. De olika alternativen för slamavvattning sammanställdes och jämfördes genom att varje undersökt parameter delades in i intervall som gav olika betyg. De tre alternativ som enligt denna undersökning ansågs bäst lämpade var att restaurera de befintliga bäddarna, att anlägga vassbäddar eller att installera en mindre silbandpress.</p><p> </p><p>Då slammet avvattnats återstår frågan kring hur det avvattnade slammet ska hanteras. Detta undersöktes genom att två alternativ studerades närmare. Dessa var att fortsätta med den nuvarande hanteringen som är kompostering och tillverkning av anläggningsjord eller att certifiera slammet genom REVAQ och sprida det på åkermark. Ett försök till att skatta kostnaden för de båda alternativen gjordes, bland annat genom att frågor ställdes till de kommuner/driftbolag som idag är certifierade enligt REVAQ. Kostnaden för certifiering och spridning på jordbruksmark är betydligt mycket högre än kostnaden för kompostering. Certifieringsalternativet innebär dock en större måluppfyllelse i och med att fosfor återförs till produktiv mark.   </p><p> </p><p>Resultatet av studien är ett konkret förslag på hur slamavvattning och avsättning för slam vid Hedesunda reningsverk kan skötas i framtiden. Detta förslag innebär att de nuvarande torkbäddarna restaureras och att möjligheterna att certifiera flera delar av Gästrike Vatten AB:s verksamhet utreds närmare. Att enbart certifiera slam från Hedesunda reningsverk anses ekonomiskt orimligt.</p> / <p>Hedesunda wastewater treatment plant (wwtp) is located in the southern part of Gävle municipality in Sweden. The wwtp treats wastewater from Hedesunda community and a few nearby villages. All in all there are approximately 1500 persons connected to the plant. Hedesunda wwtp was originally built in the 1960’s and was restored in the late 1990’s. At the restoration sludge drying beds were built on the site for sludge dewatering. Initially, these beds worked fine but since 2005 the dewatering result has not been satisfactory.</p><p> </p><p>The objective of this master thesis has been to investigate different alternatives for a more effective sludge handling at Hedesunda wwtp in the future. Initially the sludge handling process was divided into two different parts: sludge dewatering and management of dewatered sludge. The focus has been on economical and environmental aspects of sludge handling and where it’s been possible these factors have been weight together.</p><p> </p><p>The question of how a more effective dewatering of sludge could be achieved was answered by a questionnaire that was sent to different companies that supply dewatering equipment to the Swedish market. Altogether six answers were collected. Besides these answers the option of restoring the existing sludge drying beds was also considered. The latter was done by sampling and analyzing sludge in the existing beds, among other things. The different options for dewatering were compiled and compared in a matrix where every parameter was split up in intervals and assigned grades. Three options that received the highest total grade were considered the best options. These were: restoring the sludge drying beds, reed beds and a small belt filter press.</p><p> </p><p>The matter of how to handle the dewatered sludge was simplified to a study of only two alternatives. These were to continue the present handling or to certify the sludge according to REVAQ and use it as fertilizer. Attempts to estimate the cost for the two alternatives were made. The cost for certification is higher than the cost for composting, but to certify the sludge will lead to a higher target achievement.</p><p> </p><p>The study resulted in concrete suggestions for how the sludge at Hedesunda wwtp can be handled in the future. This suggestion states that the existing sludge drying beds should be restored and that the possibility to certify several wwtp:s within Gästrike Vatten AB should be investigated. It is not considered economically plausible to certify sludge from Hedesunda wwtp alone.</p>

Idag fokuserar företag mer och mer på att energieffektivisera sina verksamheter då det finns både ekonomiska och miljömässiga vinster i detta. För att minska energiförbrukningen i samhället är det bra att börja med dess infrastruktur. För att funktionen hos ett avloppsreningsverk ska vara god samtidigt som energikostnaderna hålls nere är bland annat valet av rätt pumpar och blåsmaskiner för den aktuella driftsituationen av största vikt. Att hitta balansen mellan funktion och energieffektivitet hos en kombination av maskiner är dock ett tidskrävande arbete. Genom två fallstudier och matematisk modellering var syftet med detta examensarbete att bestämma huruvida det är möjligt att grovt uppskatta livscykelkostnaden hos olika kombinationer av pumpar och blåsmaskiner i varierande driftsituationer. En sådan modell skulle hjälpa projektören att uteslutande undersöka de kombinationer av maskiner som är mest troliga att ha den lägsta livscykelkostnaden. Det har visats att det krävs en förmåga att mycket noggrant kunna förutsäga verkningsgraden hos de individuella maskinerna för att det ska vara möjligt att bestämma livscykelkostnaden så pass väl att resultatet är användbart. Sannolikt är det dock inte möjligt att finna en modell som är tillräckligt noggrann. Detta beror huvudsakligen på att mycket små förändringar av verkningsgraden ger en kraftig påverkan av livscykelkostnaden samt att verkningsgraden beror av många faktorer som är svåra att generalisera. Däribland att verkningsgraden inte förändras proportionellt till en varierande belastning på maskinen samtidigt som påverkan inte heller är densamma mellan olika maskinmodeller. Projektet har däremot mynnat ut i en ekvation för det flöde en blåsmaskin behöver generera i en given driftsituation samt ett beräkningsverktyg som underlättar undersökandet av de ingående parametrarnas inverkan på detta flödesbehov och därmed i förlängningen på livscykelkostnaden. Utöver detta slår rapporten fast att det i många fall är möjligt att sänka livscykelkostnaden med hjälp av icke frekvensstyrda maskiner. / Today companies tend to focus more and more on energy efficiency as there are both economical and environmental benefits to be gained. From a society’s point of view a good start to save energy is in its infrastructure. When designing wastewater treatment plants and their pumps and blowers choosing the right machines for the right operational circumstances is crucial to make it all work together and lower the energy cost at the same time. But to weigh the function against the energy efficiency of a combination of machines is a time consuming effort. Through two case studies and mathematical modeling this thesis project aimed to determine whether it is possible to roughly predetermine the life cycle cost of different combinations of pumps and blowers in variable operational circumstances. This would help the process engineers to focus their time and effort on the combinations of machines that are the most probable to have the lowest life cycle cost. The results show that the ability to accurately predetermine the efficiency of the individual machine is crucial to determine the life cycle cost to a usable degree. Unfortunately it doesn't seem feasible to find a model that will be accurate enough to be of practical use. This is due to the fact that slight changes to the efficiency cause great changes to the life cycle cost and that the efficiency depends on several factors that are hard to predict including the fact that it does not change proportionally to a variable load.

Hedesunda reningsverk är beläget i södra delen av Gävle kommun och hanterar avloppsvatten från Hedesunda samhälle och ett fåtal närbelägna byar. Antalet anslutna personer är strax över 1500. Reningsverket byggdes på 1960-talet och byggdes om i slutet av 1990-talet. Vid ombyggnaden anlades torkbäddar för avvattning av det slam som produceras vid reningsverket. Inledningsvis fungerade dessa torkbäddar bra men sedan 2005 har slammet i bäddarna inte avvattnats i önskad omfattning.   Syftet med detta examensarbete var att utreda hur slamavvattningen i Hedesunda ska se ut i framtiden. Utgångspunkten var att den nuvarande lösningen är otillräcklig och att en förändring är nödvändig. Inledningsvis delades frågeställningen upp i två separata delar: avvattning av slammet och avsättning för avvattnat slam. Fokus låg på ekonomiska och miljömässiga aspekter av slamhantering och en sammanvägning av dessa gjordes där så var möjligt.   Frågan om hur avvattningen bör se ut undersöktes genom att en enkät skickades ut till nio olika företag som levererar avvattningsutrustning. Dessa fick svara på 17 frågor om vilken lösning de ansåg vara bäst lämpad för reningsverket i Hedesunda. Sammanlagt samlades sex olika svar in. Utöver dessa undersöktes även alternativet att restaurera de befintliga torkbäddarna närmare. Detta skedde bland annat genom provtagning och analys av slammet i bäddarna. De olika alternativen för slamavvattning sammanställdes och jämfördes genom att varje undersökt parameter delades in i intervall som gav olika betyg. De tre alternativ som enligt denna undersökning ansågs bäst lämpade var att restaurera de befintliga bäddarna, att anlägga vassbäddar eller att installera en mindre silbandpress.   Då slammet avvattnats återstår frågan kring hur det avvattnade slammet ska hanteras. Detta undersöktes genom att två alternativ studerades närmare. Dessa var att fortsätta med den nuvarande hanteringen som är kompostering och tillverkning av anläggningsjord eller att certifiera slammet genom REVAQ och sprida det på åkermark. Ett försök till att skatta kostnaden för de båda alternativen gjordes, bland annat genom att frågor ställdes till de kommuner/driftbolag som idag är certifierade enligt REVAQ. Kostnaden för certifiering och spridning på jordbruksmark är betydligt mycket högre än kostnaden för kompostering. Certifieringsalternativet innebär dock en större måluppfyllelse i och med att fosfor återförs till produktiv mark.      Resultatet av studien är ett konkret förslag på hur slamavvattning och avsättning för slam vid Hedesunda reningsverk kan skötas i framtiden. Detta förslag innebär att de nuvarande torkbäddarna restaureras och att möjligheterna att certifiera flera delar av Gästrike Vatten AB:s verksamhet utreds närmare. Att enbart certifiera slam från Hedesunda reningsverk anses ekonomiskt orimligt. / Hedesunda wastewater treatment plant (wwtp) is located in the southern part of Gävle municipality in Sweden. The wwtp treats wastewater from Hedesunda community and a few nearby villages. All in all there are approximately 1500 persons connected to the plant. Hedesunda wwtp was originally built in the 1960’s and was restored in the late 1990’s. At the restoration sludge drying beds were built on the site for sludge dewatering. Initially, these beds worked fine but since 2005 the dewatering result has not been satisfactory.   The objective of this master thesis has been to investigate different alternatives for a more effective sludge handling at Hedesunda wwtp in the future. Initially the sludge handling process was divided into two different parts: sludge dewatering and management of dewatered sludge. The focus has been on economical and environmental aspects of sludge handling and where it’s been possible these factors have been weight together.   The question of how a more effective dewatering of sludge could be achieved was answered by a questionnaire that was sent to different companies that supply dewatering equipment to the Swedish market. Altogether six answers were collected. Besides these answers the option of restoring the existing sludge drying beds was also considered. The latter was done by sampling and analyzing sludge in the existing beds, among other things. The different options for dewatering were compiled and compared in a matrix where every parameter was split up in intervals and assigned grades. Three options that received the highest total grade were considered the best options. These were: restoring the sludge drying beds, reed beds and a small belt filter press.   The matter of how to handle the dewatered sludge was simplified to a study of only two alternatives. These were to continue the present handling or to certify the sludge according to REVAQ and use it as fertilizer. Attempts to estimate the cost for the two alternatives were made. The cost for certification is higher than the cost for composting, but to certify the sludge will lead to a higher target achievement.   The study resulted in concrete suggestions for how the sludge at Hedesunda wwtp can be handled in the future. This suggestion states that the existing sludge drying beds should be restored and that the possibility to certify several wwtp:s within Gästrike Vatten AB should be investigated. It is not considered economically plausible to certify sludge from Hedesunda wwtp alone.

Most of wastewater treatment plants (WWTP) are operated under low loading both in water quality and water capacity (flow rate) in Taiwan. Because various treatment methods used in WWTP would cause different power consumptions. In general, the flow rate of wastewater treated is proportional to the power consumption. The purpose of this study is simulating water quality and water capacity with a case of municipal wastewater treatment plant, using standard activated sludge method. In this work we will investigate the feasibility of save power using operation and parameters adjustment in wastewater system. A further step is to conduct the save energy in current WWTP under normal wastewater treatment capacity and national effluent standard. Results showed the major save energy was at inflow pump and aeration system of biological treatment stage. Both power consumptions of two were about 60 ~70 % of total power consumption in the plant. Thus we should focus the operating conditions to plan the save energy project, and calculate the total power system and energy consumption of all unit facilities before we are going to improve the energy save in WWTP. Important note is firstly to select units and facilities having high energy consumption for evaluating the possibility of energy save. Secondly is develop and using a good management system to attain the goal of save energy.

In natural waters, high concentrations of ammonia are toxic to fish, and the oxidation of ammonia to nitrate (NO₃-) consumes large quantities of dissolved oxygen. The influent to municipal wastewater treatment plants in the United States typically contains approximately 40 mg/L of ammonia nitrogen (NH₃₋ N). Almost all of this ammonia must be removed in a wastewater treatment process before the effluent is discharged to the natural environment. This dramatic decrease is accomplished by the aerobic biological process of nitrification, in which ammonia is oxidized to nitrate Biological denitrification is an anoxic biological process in which nitrate (NO₃-) is reduced to nitrogen gas (N₂). Denitrification can increase the alkalinity in activated sludge aeration basins and decrease the concentration of filamentous organisms. The staff at the City of Austin Water Utility decided to implement a denitrification system at Walnut Creek Wastewater Treatment Plant to control filamentous organisms and increase the alkalinity within the aeration basins. The denitrification configuration that the staff implemented was unconventional because no structural changes were made to the aeration basins to encourage denitrification. However, the system functioned well and allowed operators to turn off one of the two air blowers, which saves the plant a significant amount of energy. The current operation has occasional problems, where the alkalinity in the aeration basin decreases or the effluent ammonia increases. When the alkalinity decreases to the point where the pH drops to near 6.0, operators are forced to add chemicals to increase the alkalinity. When the effluent ammonia increases to near the permitted concentration (2.0 mg NH₃-N/L),operators are forced to turn back on the second blower which eliminates the anoxic zone. These problems occur most often during the winter, when the wastewater is the coldest. The wastewater temperature at Walnut Creek varies from a high of 30°C during the summer to a low of 18°C during the winter. The goal of this research was the identification of ways to make the operation more robust which would prevent the need for chemical addition and minimize the use of the second blower. Laboratory-scale reactors were operated to assess possible improvements that could be made to the operation and configuration of the denitrification system at Walnut Creek. The data observed in the laboratory scale experiments showed that the population of denitrifying bacteria limits denitrification and is especially important during the winter. Increasing the solids retention time to 20 days appeared to be the best way to increase the population of denitrifying bacteria and improve denitrification. Improvements can also be made by increasing the volume of the anoxic zone. Increasing the volume of wastewater and biomass recycled will most likely not benefit denitrification until other improvements have been made. Recommendations to the City of Austin Water Utility include the following: 1) increase the solids retention time at Walnut Creek, 2) Increase the volume of the anoxic zone, 3) Separate the anoxic zone from the aerobic section of each aeration basin, 4) During the winter, operate the flow equalization basins to reduce the dissolved oxygen entering the anoxic zone, 5) Continually mix some of the effluent from the aeration basins with the primary effluent in the flow equalization basins. / text

Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1990. / Vita. Abstract. Includes bibliographical references (leaves 150-155). Also available via the Internet.