The microbial populations in the Hoechst-Celanese activated sludge were examined. Heterotrophs, denitrifiers, sulfate-reducers, protozoa and filamentous bacteria were enumerated. Variations in microbial populations were compared with influent and effluent constituent concentrations, and with aeration basin characteristics, such as dissolved oxygen and F/M ratio, to determine whether any microbial type could be used by plant operators to monitor process performance. Results indicated that filamentous bacteria may be useful to plant operators for monitoring process performance because an inverse relationship between filamentous bacteria, food-to-microorganism ratio and sludge volume index was suggested by this study. Protozoa may also be useful for operators, although more data is needed. Microthrix parvicella and Type 0041 were the most common filament types. Filament Type 1701 was most prevalent during a period of low dissolved oxygen. A strong relationship between stalked ciliates and effluent quality was mention in the literature, but was not found in this study. Enumeration methods were evaluated. / Master of Science

The performance of fibrous biomass support media (Ringlace) and porous spongelike biomass support media (Captor) was evaluated for enhanced nitrification and denitrification in a pilot-scale Virginia Initiative Project (VIP) biological nutrient removal (BNR) process. Four separate pilot-scale treatment trains were constructed and operated during this research. Three of the four treatment trains were operated with fixed film media (Ringlace/Captor) incorporated in the aerobic zone of the system and are referred to as the Integrated Fixed Film Activated Sludge (IFAS) systems. A fourth treatment train (Control train) was operated without any fixed film media. All experiments in this research were performed using domestic wastewater from Blacksburg, Virginia, and the Virginia Tech campus. Enhanced nitrification was observed in the IFAS system containing porous biomass support media (Captor) that was freely suspended in the mixed liquor of the aerobic zone. Near-complete nitrification was observed in the IFAS system containing Captor media even at total suspended growth MCRTs as low as 5.6 days and a 12°C liquid temperature. Significantly higher nitrification rates were observed in the IFAS system containing Captor media compared to both the IFAS system containing Ringlace media and the control train. However, there was less denitrification in the aerobic zone of the IFAS systems containing Captor media compared to the Ringlace media systems. Enhanced nitrification could not be statistically shown in the IFAS system containing Ringlace media. The overall nitrification rates in the Ringlace media system were about the same as the control train for the MCRTs and temperatures used during this research. However, a significantly greater amount of denitrification was observed in the aerobic zone of the IFAS system containing Ringlace media compared to both the IFAS system containing Captor media and the control system. Microscopic examination of the growth on the fixed film media (Ringlace and Captor) showed that red worms always grew on the Ringlace media, and were detrimental to performance on at least one occasion. Methods for controlling the worms were developed and applied successfully. During certain operating phases, lower sludge productions and observed sludge yields were measured in the IFAS system containing Ringlace media. However, a Statistical difference could not be calculated between the sludge production in the Ringlace media system and the control system. Lower sludge production and observed sludge yield were also observed in the IFAS system containing Captor media, but only two data points were available and a Statistical t-test analysis was not possible. / Master of Science

<p>Slamsvällning orsakar stora problem i avloppsreningsverk med biologisk rening i aktivt slamprocesser. Slamsvällning orsakas av filamentösa (trådformiga) bakterier, som inverkar negativt på slammets sedimenteringsegenskaper.</p><p>Himmerfjärdens vattenreningsverk har drabbats av detta problem som leder till ett stabilt lager av slam på ytan av sedimenteringsbassängen som inte sedimenterar.</p><p>För att lösa detta problem behandlades returslammet från sedimenteringsbassängen med ozon för att minska mängden filamentösa bakterier i returslamflödet. Ozon är en starkt oxiderande gas, som är väl användbar för icke-specifik bekämpning av slamsvällning. När ozon kommer i kontakt med den filamentösa bakteriens cellvägg penetreras det in i cellen, varvid cellen lyserar.</p><p>Ozonbehandlingen resulterade i en förminskning av antalet filamentösa bakterier. Ozonbehandling av returslam förbättrade sedimenteringsegenskaperna hos svällande slam utan att påverka andra viktiga mikrobiologiska processer t.ex. nitrifikation.</p> / <p>Bulking sludge causes major problems in wastewater treatment plants that deal with biological nutrient removal in activated sludge processes. Bulking sludge is caused by filamentous bacteria, which have a negative impact on the sludge settling properties.</p><p>Himmerfjärden wastewater treatment plant suffers from this type of problem with bulking sludge which creates a stable layer at the surface that does not settle in the clarifier.</p><p>In order to solve this problem, on site generated ozone was used to decrease the amount of filamentous bacteria in the return activated sludge flow. Ozone is a strong oxidant is suitable for non-specific bulking control. It stresses the filamentous bacteria causing inactivation through cell wall disintegration.</p><p>The ozone treatment resulted in decreased abundance of filamentous bacteria. Ozone treatment of the recycled activated sludge improves the settling properties of bulking sludge, without interfering with other important microbiological processes e.g. nitrification.</p>

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2017. / For more than a decade, poultry product consumption increased in developed and developing countries, with more than 470 new slaughterhouses being constructed in South Africa (SA). Customer demand for poultry products resulted in a rapidly growing poultry industry, with consequential increases in the quantity of organic solid and liquid waste being produced from the poultry slaughterhouses. Annually, the productivity and profitability within the livestock production sector has increased, an evaluation based on the number of slaughtered and sold animals. Potable water is required for these animals, resulting in the generation of high strength wastewaters. Instantaneous disposal of such wastewaters into the environment is concerning as it results in odour and the spreading of diseases in local rivers and freshwater sources. The generated poultry slaughterhouse wastewater (PSW) contains a high quantity of biodegradable organic, suspended and colloidal matter in the form of proteins, fats, oil and grease (FOG), protein from meat, blood, skin, and feathers, resulting in high Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD), which can contribute to environmental deterioration if not treated adequately before discharge. On average, PSW contains a high concentration of BOD, COD, nitrogen, pathogenic and non-pathogenic viruses, bacteria and parasites, including their eggs. These characteristics make PSW highly polluted with a large quantity of bird carcass debris including FOG. Due to the high concentration of organic matter and suspended solids in the wastewater, it is necessary to pre-treat the PSW prior to sequential anaerobic treatment. Most of the contaminants present in the PSW can be reduced by means of numerous treatment steps, i.e. physical, chemical and biological treatment. For this study, biological treatment methods, physical separation methods, and a membrane bioreactor system, were used to treat PSW. The biological treatment methods used were an anaerobic digester (AD) followed by a single stage nitrification/denitrification reactor and then a third stage in which an ultrafiltration (UF) and Microfiltration (MF) membrane bioreactor (MBR) was used. The AD used was an Expanded Granular sludge Bed Reactor (EGSB) as anaerobic digestion is one of the most effective biological wastewater treatment methods used, as it reduces the organic matter to even produce biogas as a renewable energy source. The basis of anaerobic treatment method relies on suitable bacteria cultivated in the absence of dissolved oxygen, facilitating decomposition of organic matter into a renewable source such as biogas. Similarly, biological nitrification/denitrification processes for the removal of total nitrogen (TN) in wastewater has become one of the most commonly used processes within the wastewater treatment sector. Nitrification and denitrification processes can be performed by some microorganisms within the wastewater in Wastewater Treatment Plants (WWTPs) The PSW used was collected at different times from a local poultry slaughterhouse in the Western Cape (South Africa) and stored in a refrigerator at 4°C until it was fed to the first stage of the treatment which was the EGSB. Before being fed to the EGSB, the PSW was filtered with a sieve to remove feathers and agglomerated FOG to avoid clogging of the tubing. The EGSB was inoculated with 0.747 L anaerobic granular sludge, had a working volume of 2.7 L, an inner diameter of 0.065 m and a height of 0.872 m respectively. Ceramic marbles with an average diameter of 0.0157m were placed at the bottom of the bioreactor as packing for the underdrain and to maintain the granular sludge within the heated section of the bioreactor. The EGSB was fed with three types of PSW: 50% (v/v), 70% (v/v), which was diluted with distilled water. Thereafter once the system stabilised the reactor was fed with undiluted PSW (100%). Each dilution was operated at different Hydraulic Retention Times (HRTs) and Organic Loading Rates (OLRs), with average HRTs used being 62.5, 57.5 and 49.65 h. Furthermore, the average OLRs were 1, 2 and 3 g tCOD/L.day respectively. The performance of the EGSB was determined using tCOD, Total Suspended Solids (TSS) and FOG, with overall averaged removal rates for these constituents being 69%, 98% and 92% respectively. The highest tCOD removal of 93 % (optimal efficiency) was obtained at an average HRT of 57.5 h with a corresponding average OLR of 2 g tCOD/L.day.

<p>This thesis concerns modeling and control of bilinear systems (BLS). BLS are linear but not jointly linear in state and control. In the first part of the thesis, a background to BLS and their applications to modeling and control is given. The second part, and likewise the principal theme of this thesis, is dedicated to theoretical aspects of identification, modeling and control of mainly BLS, but also linear systems. In the last part of the thesis, applications of bilinear and linear modeling and control to the activated sludge process (ASP) are given.</p>

More stringent requirements on nitrogen removal from wastewater are the motivation for this thesis. In order to improve treatment results and enhance cost-efficient operation of wastewater treatment plants, model based control strategies are presented. A Java based simulator for activated sludge processes (JASS) is presented. The graphical user interface, educational experiences and implemented control strategies are discussed. Controlling the addition of an external carbon source is the next topic discussed. A simple model based feedforward controller is derived and evaluated in a simulation study. The controller attenuates process disturbances quickly. Further, two feedforward controllers for adjusting the aeration volume in activated sludge processes are derived. The aim of the volume control strategies was to efficiently dampen the impact of process disturbances without using an excessively high dissolved oxygen concentration. The simulation results are promising and show that the aeration volume may be a feasible control variable. A linearisation method for static input non-linearities is presented. The method gives essentially the same result as the existing standard method, but possesses some implementational advantages. The method is used to linearise the non-linear oxygen transfer function of an activated sludge process in an application study. Multivariable interactions in a process model describing nitrate removal in an activated sludge process are studied using the well known RGA method as well as a relatively novel tool based on Hankel norms. The results of the analysis are compared to conclusions drawn from common process knowledge and are used to design a multivariable control strategy. It was found that process disturbances may be rejected faster using multivariable control. Finally, the operational costs of the denitrification process are investigated and visualised graphically. Cost optimal regions are found by a numerical grid search. Procedures for controlling the denitrification process in a cost-efficient way are described.

Slamsvällning orsakar stora problem i avloppsreningsverk med biologisk rening i aktivt slamprocesser. Slamsvällning orsakas av filamentösa (trådformiga) bakterier, som inverkar negativt på slammets sedimenteringsegenskaper. Himmerfjärdens vattenreningsverk har drabbats av detta problem som leder till ett stabilt lager av slam på ytan av sedimenteringsbassängen som inte sedimenterar. För att lösa detta problem behandlades returslammet från sedimenteringsbassängen med ozon för att minska mängden filamentösa bakterier i returslamflödet. Ozon är en starkt oxiderande gas, som är väl användbar för icke-specifik bekämpning av slamsvällning. När ozon kommer i kontakt med den filamentösa bakteriens cellvägg penetreras det in i cellen, varvid cellen lyserar. Ozonbehandlingen resulterade i en förminskning av antalet filamentösa bakterier. Ozonbehandling av returslam förbättrade sedimenteringsegenskaperna hos svällande slam utan att påverka andra viktiga mikrobiologiska processer t.ex. nitrifikation. / Bulking sludge causes major problems in wastewater treatment plants that deal with biological nutrient removal in activated sludge processes. Bulking sludge is caused by filamentous bacteria, which have a negative impact on the sludge settling properties. Himmerfjärden wastewater treatment plant suffers from this type of problem with bulking sludge which creates a stable layer at the surface that does not settle in the clarifier. In order to solve this problem, on site generated ozone was used to decrease the amount of filamentous bacteria in the return activated sludge flow. Ozone is a strong oxidant is suitable for non-specific bulking control. It stresses the filamentous bacteria causing inactivation through cell wall disintegration. The ozone treatment resulted in decreased abundance of filamentous bacteria. Ozone treatment of the recycled activated sludge improves the settling properties of bulking sludge, without interfering with other important microbiological processes e.g. nitrification.

På Käppalaverket i Stockholm står luftningen av de biologiska bassängerna för omkring en femtedel av verkets totala elenergiförbrukning. I ett försök att minska energikostnaden utvärderades under hösten 2010 nya metoder för luftflödesreglering på verket. Grundtanken var att styra luftflödet efter medelvärdet på utgående ammoniumkoncentration under en längre tid, istället för som idag efter momentana värden. Ett vanligt sätt att styra luftflöden på reningsverk idag är att använda återkoppling från utgående ammoniumkoncentration, vilket syftar till att alltid hålla den utgående koncentrationen vid ett valt börvärde. Lagstiftade gränsvärden på ammonium avser dock normalt medelvärden över en längre tid, såsom kvartal eller år. Istället för att anpassa luftflödet efter den inkommande belastningen är det därför möjligt att hålla luftflödet relativt konstant medan istället den utgående koncentrationen tillåts variera. I denna studie visades en energibesparing kunna erhållas om luftflödets variation reduceras. Två strategier utvärderades i vilka luftflödet respektive syrehalten hölls så konstant som möjligt. Dessa jämfördes med den idag använda styrstrategin på Käppalaverket, i vilken luftflödet anpassas efter den inkommande belastningen genom återkoppling. Studien inkluderade både simuleringar i modellen Benchmark Simulation Model no. 1 och fullskaleförsök på Käppalaverket. I både simuleringar och fullskaleförsök resulterade de två utvärderade strategierna i en lägre luftförbrukning per reningsgrad än den idag använda återkopplingsstrategin. I fullskaleförsöken erhölls en luftflödesreduktion på 11 % då luftflödet hölls konstant och 15 % då syrehalten hölls konstant. Båda strategierna genererade dock en kraftigt varierande utgående ammoniumkoncentration. Variationerna var störst då luftflödet hölls konstant och korrelerade inte med den dygnsbaserade belastningsprofilen. Sammanfattningsvis visade studien att en reducering av luftflödets variation resulterar i en lägre luftförbrukning men också i en ökad instabilitet. En konstant syrehalt gav en större energivinst och även en stabilare ammoniumreduktion än ett konstant luftflöde, varför denna metod har störst potential till vidare implementering i fullskala. / The aeration of the bioreactors is responsible for one fifth of the energy consumption at the Käppala wastewater treatment plant (WWTP) in Stockholm. In this report, new methods for aeration control were evaluated in order to reduce the energy costs at the plant. The main idea was to control the effluent ammonia concentration in terms of mean values instead of momentary values. A quite common approach for aeration control is to use feedback from the effluent ammonia concentration, thus aiming to keep the effluent concentration consistently at a certain set point. However, discharge limits normally refer to mean values over longer periods of time, such as months or years. Instead of adjusting the airflow to the incoming load it is therefore possible the keep the airflow fairly constant while allowing a fluctuating effluent concentration. In this paper, it was shown that by reducing the variation of the airflow, energy could be saved. Two methods were evaluated in which the airflow and oxygen concentration respectively was held constant. These methods were compared to the control strategy used today at the Käppala WWTP, where feedback control adjusts the airflow to the influent load. The study consisted of simulations with the Benchmark simulation model no. 1 (BSM1) as well as full scale experiments at the Käppala WWTP. Both the simulations and full scale experiments showed a reduced aeration per nutrient removal for the evaluated methods. In full scale, the total airflow reduction was 11 % when the airflow was held constant and 15 % when the oxygen concentration was held constant. However, the methods resulted in large variations of the effluent ammonia concentration, which did not correlate to the daily influent load. The variations were especially large when the airflow was held constant. In summary, this study showed that a reduced airflow variation results in lower aeration costs but also less stability. A constant oxygen concentration required less aeration and provided a more stable degree of ammonia removal than a constant airflow. For this reason, aeration control with a constant oxygen concentration has the best potential for further use at the Käppala WWTP.

published_or_final_version / Civil and Structural Engineering / Master / Master of Philosophy

Phylogenetic hybridization and phenotypic fingerprinting were applied to the analysis of bacterial communities in wastewater treatment systems. These approaches were aimed at (i) developing monitoring tools able to foresee operational problems, and (ii) providing the rationale to optimize the operation of bioreactors. The work presented is intended to first describe the community found in two reactors treating pulp and paper mill effluent, and second evaluate the possibilities of these techniques with respect to the development of new monitoring tools. / Phylogenetic membrane hybridization showed that the bacterial communities were dominated by Alpha and Beta Proteobacteria, a structure probably linked to the low F:M ratio. Other important factors determining the community structure were the proportion of COD in the high molecular weight fraction, the sludge age, phosphate addition, and the concentration of specific compounds (alcohols, phenols, volatile fatty acids) in the influent. The community structure partly determined the sludge characteristics demonstrating its potential value in the assessment of reactor performance. The results obtained by phylogenetic membrane hybridization suggest that the probes used in a monitoring tool would not need to be targeted to the species level to provide relevant information. However, they also suggest that the technique is more sensitive to changes in population density as opposed to changes in bacterial metabolism. / Phenotypic fingerprinting measured a smaller difference between the communities of the two reactors studied than what was measured by phylogenetic membrane hybridization. However, differences in heterotrophic activities observed between the two communities were linked to differences in influent composition.