Nitrification, a key step in biological nitrogen removal processes, is the oxidation of ammonia into nitrate performed by ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) under aerobic condition. Researchers have focused on factors affecting the performance of nitrification for decades, but the inorganic carbon limitation on nitrification had been neglected. However, the increase in nitrogen in wastewater has increased the need to evaluate and improve our understanding of this limitation. In a previous research, the hypothesis that different inorganic carbon concentrations would enrich different AOB populations has been examined. In this study, the focus was on the effect of inorganic carbon concentration on NOB, which has a close relationship with AOB. Two 5L lab–scale continuous–flow stirred tank reactors (CSTR) were operated to evaluate the nitrification performance and microbial ecology of nitrifier populations acclimated under inorganic carbon sufficient (high–IC) and limited (low–IC) conditions for approximately 700 days. During the operation period, both bioreactors were able to maintain satisfactory nitrification efficiency higher than 95% at an influent ammonium concentration of 250 mg–N/L. Nitrate was the major end product and no significant nitrite accumulation was observed. To evaluate the effects of inorganic carbon on NOB community structures, cloning/sequencing and real–time PCR were applied to target and quantify the two common NOB genera, Nitrospira and Nitrobacter, as no molecular probe targeting all known NOB is available presently. The results showed that these two genera were both found in the two reactors. Nitrospira was the dominant NOB population in the high–IC bioreactor, while Nitrobacter was dominant in the low–IC one after one year acclimation. Kinetic analysis revealed that NOB enriched in the two reactors have different kinetic performances. However, IC concentration did not show a significant impact on the nitrite oxidizing kinetics of NOB in the batch tests.

Floodplain lakes are wetlands which receive flood waters from nearby rivers or other sources. Water samples were taken from floodplain lakes near the Illinois River, the Mississippi River, and the Cache River in Southern Illinois. Fluorescence in situ hybridization (FISH), spectrophotometry, and gene probes were used to investigate the effect of nutrient and chemical concentrations on the abundance of nitrifying bacteria; specifically ammonia-oxidizing Nitrosococcus and Nitrosomonadales and nitrite-oxidizing Nitrospira and Nitrobacter. Nitrosococcus was the dominant ammonia-oxidizing bacteria at each river system. Nitrospira and Nitrobacter had similar average abundances. Nitrosococcus abundances showed a significant positive correlation with nitrate (NO3-) (R2= 0.247, P=0.05, 95% confidence R2≥0.199) and a positive trend with nitrite (NO2-) (R2= 0.194, P=0.10, 90% confidence R2≥0.125). Nitrosomonadales abundance positively correlated with temperature (R2= 0.530, P=0.05, 95% confidence R2≥0.510). Nitrospira abundances positively correlated with ammonium (NH4+) (R2= 0.265, P=0.05, 95% confidence R2≥0.199), NO2- (R2= 0.372, P=0.05, 95% confidence R2≥0.199), and NO3- (R2= 0.482, P=0.05, 95% confidence R2≥0.199). None of the target bacterial abundances significantly correlated with pH or dissolved inorganic phosphate.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20009号 / 農博第2193号 / 新制||農||1045(附属図書館) / 学位論文||H28||N5018(農学部図書室) / 33105 / 京都大学大学院農学研究科応用生命科学専攻 / (主査)教授 小川 順, 教授 阪井 康能, 教授 栗原 達夫 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

Due to the adverse effects of ammonia on the environment, many governments, including Canada, have imposed new regulations to reduce the discharge of ammonia wastewater effluent into natural receiving waters, which has resulted in the upgrade of ammonia removal at water resource recovery facilities (WRRFs) across the world. There is therefore a need to investigate present urban/peri-urban and rural challenges associated with municipal total ammonia (TAN) removal. In particular, there is a need to further advance and optimize technologies such as the moving bed biofilm reactor (MBBR) to meet these critical challenges. The first objective of this thesis is to validate an elevated loaded strategy for partial nitritation (PN) MBBR as an application for mainstream urban and peri-urban municipal wastewater treatment and to elucidate the mechanism of nitrite-oxidation suppression of this system. The second objective is to identify practical storage strategies for nitrifying MBBR units as rural municipal wastewater upgrade systems (lagoon systems), optimizing the TAN removal performance during seasonal discharge periods. In the context of the present climate change crisis and sustainable development requirements, there is an increased need for efficient TAN removal from urban and peri-urban municipal wastewaters. The application of the energy and cost-efficient partial nitritation/anammox (PN/A) technology to mainstream urban and peri-urban municipal wastewater can prove challenging because of limited ability to achieve the stable PN. Hence, there is a need for the validation of the present strategies for achieving effective and stable PN in the mainstream portion of conventional urban and peri urban WRRFs. The 45 days operation of a laboratory-scale, elevated loaded PN MBBR with average surface area loading rate (SALR) of 5.2 ± 0.1 g TAN/m²·d and a hydraulic retention time of 2h showed a successful and stable nitrite accumulation. The average surface area removal rate (SARR) of 2.3 ± 0.2 g TAN/m²·d (theoretical performance objective of 2.7 g TAN/m²·d), TAN removal efficiency of 43.1 ± 3.4% (theoretical performance objective of 53%) and NO₂- / (NO₂- + NO₃-) ratio of 82.4 ± 4.8% (theoretical performance objective of 100%) meets the necessary requirement to support subsequent cost-efficient anammox process. Biofilm analyses of the laboratory-scale, elevated loaded PN MBBR indicated that the attached biofilm was thick and dense, stable biofilm that did not show and biofilm loss or washout. Biofilm cell viability analyses was indicative of an active biofilm. The ratio of AmoA gene targets of the ammonia oxidizing bacteria (AOB) in the MBBR biofilm to the targeted gene region of the Nitrospira nitrite oxidizing bacteria (NOB) population demonstrates that NOB activity suppression of this technology was the dominant mechanism of nitrite-oxidation in the elevated loaded PN MBBR system. In North America, the TAN removal performance of waste stabilization ponds (also termed wastewater treatment lagoon systems), which are widely applied as rural WRRFs, is often not stable due to seasonal temperature variations. Nitrifying MBBR as an upgrade TAN removal unit has been successfully applied to improve TAN removal during winter. However, re-seeding the nitrifying MBBR biofilm during each seasonal operation period is not sustainable. There is therefore an urgent need for optimizing storage strategies of nitrifying MBBR carriers when used as TAN removal upgrade systems of rural WRRFs. The study of storage strategies for nitrifying MBBR as lagoon upgrading systems indicated the batch storage of the nitrifying MBBR biofilms with intermittent aeration could be an effective storage strategy for short-term (12 weeks) storage. Carriers stored in continuous flow aerated condition was shown to be the second most suitable storage method for nitrifying MBBR carriers for systems exposed to less than 12 weeks of storage. Carriers stored in dry condition, batch aerated conditions without flow, and continuous flow aerated condition for long-term (over 18 weeks) failed to achieve full nitrification following 18 days of operation conditions. Carriers stored in dry condition did not successfully achieve full nitrification for short-term and long-term storage and may not be applied to store full nitrification MBBR carriers. The study suggested that, compared to re-seeding start up strategy of the lagoon upgrading nitrifying MBBR biofilm, the use of the appropriate storage strategies, such as batch aerated conditions without flow, has the potential to shorten the start-up time and save energy during the non-discharge periods.

Understanding how nitrifiers react when exposed to low DO conditions could provide a greater understanding of low DO operations in full-scale biological wastewater treatment. Previous methods to observe nitrifier oxygen kinetics do exist in literature, however they are inefficient and labor intensive. Other more efficient methods require the use of selective inhibitors, which alter the characteristics of the biomass. This study developed a time and labor efficient respirometric method to distinctly measure oxygen half-saturation coefficients for both ammonia oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) without the use of selective inhibitors. By eliminating the use of inhibitory substances, representative biomass characteristics were maintained throughout the tests. The developed method, called the declining DO method, consisted of using a high-speed dissolved oxygen (DO) probe to measure relative oxygen uptake rates (OUR) within a batch reactor when varying substrates (ammonia and nitrite) were present in excess within the system. A forward model was developed based on Monod kinetics to simultaneously fit Monod curves to the experimental OUR data. These curves were fit by solving for optimum oxygen kinetic parameters representing endogenous respiration, NOB, and AOB. An inverse model using Markov chain Monte Carlo analysis was applied to the results found in the forward model to provide statistical validation of the proposed respirometric method. A separate method, called the substrate utilization rate test, was conducted in parallel with the declining DO tests to compare and verify oxygen half-saturation coefficient results. Parallel tests were conducted using biomass samples from three different Hampton Roads Sanitation District (HRSD) full-scale facilities. Operating conditions between the three HRSD facilities were considered when performing parallel testing, including averages for DO, solids retention time (SRT), and floc size. Average floc size was found to have a significant effect on the observed oxygen half-saturation values. Observed trends for the KO values estimated using the two methods remained consistent throughout all tests, where KO,NOB was always lower than KO,AOB. The comparison of the two methods highlighted some faults associated with the substrate utilization rate test, which is commonly used in literature to observe nitrifier oxygen kinetics. The declining DO method appeared to be more resistant to potential experimental error and required less than half the time compared to the substrate utilization rate test. The development of the declining DO method without the use of selective inhibitors provided a more time and labor efficient technique for estimating apparent KO values for NOB and AOB without sacrificing biomass characteristics representative of the full-scale treatment process. Biomass samples collected from variable treatment process conditions yielded consistent parallel test results, providing further evidence that the proposed declining DO method can be a robust and reliable technique for distinctly measuring apparent oxygen half-saturation values for NOB and AOB. / Master of Science / Wastewater treatment operations utilizing biological nitrogen removal (BNR) require a continuous supply of oxygen for aerobic processes. Energy costs associated with aeration generally accounts for at least 50% of the total energy consumption at conventional activated sludge wastewater treatment facilities. Operating aerobic zones at low average dissolved oxygen (DO) concentrations could be an effective way to significantly reduce aeration costs as well as material costs associated with BNR treatment processes. This study developed a method to measure oxygen kinetics for the two groups of autotrophic bacteria responsible for performing nitrogen removal. The method consisted of measuring relative oxygen uptake rates (OUR) within a batch reactor when varying substrates were available. This method is unique from previously developed techniques in that the use of selective inhibitors was not included, meaning the characteristics of the wastewater were largely unchanged and therefore better represent biomass conditions within the full-scale process. The results of the proposed method were verified using an alternate method for estimating oxygen kinetics. These two methods were conducted in parallel using biomass samples from several full-scale Hampton Roads Sanitation District wastewater treatment facilities utilizing a variety of process designs and operating conditions. Consistent results obtained between the two methods suggested the proposed method is an effective technique for distinctly measuring nitrifier oxygen kinetics.

No description available.

Deammonification is a widely used technology for side stream treatment with rich ammonium streams at relatively high temperatures, such as, the reject water coming from dewatering units in treatment of digested sludge and industrial wastewaters. The deammonification process has lower operational costs than conventional systems, consumes less energy, enables the increase of biogas production and it is easy to implement. However, this technology has not yet been applied in full- scale mainstream treatment due to its restrictions in coping with high C/N ratios, low temperatures, and the need for post-treatment processes. These conditions are allegedly negative to the growth and performance of anammox bacteria affecting the bacterial groups’ behavior in the process. This master thesis project aimed to evaluate the feasibility of using deammonification to remove nitrogen from mainstream wastewater, which was studied by monitoring the bacterial activity in a pilot scale reactor. The different bacterial groups involved (AOB, NOB, heterotrophs, and denitrifiers) were monitored by weekly measuring their activity in batch activity tests. The results allowed the evaluation of different operational scenarios and their impact by following up on the changes in the bacterial competition. The study was conducted for six months in a single-stage IFAS (integrated fixed-film activated sludge) pilot-scale reactor located in Stockholm and fed with pretreated (with a UASB) municipal wastewater. The different operational scenarios involved changes in temperature, aeration patterns, DO concentration, SRT, and HRT. The adjustment of these features was done in the interest of promoting AOB and anammox bacterial growth, leading to an improvement of the deammonification efficiency in future studies. However, the chosen operational conditions were to enhance bacterial competition and facilitate its visualization, not to maximize nitrogen removal. Thus, the most suitable scenario found during this study included DO concentration of 1.5 mg/L with 10 aeration-20 non-aeration pattern and ensured nitrogen removal rates within normal values while allowing the monitoring of all the bacterial groups. TN removal reached a value above 50% and NH4-N above 95%, whereas nitrogen Removal Rate (NRR) increased to 30g/N/m3-d and the system had an overall nitrogen removal efficiency of 75%. Nevertheless, it was proven that in the right environment, the necessary bacterial groups can be selectively accumulated and successfully perform deammonification and reduce nitrogen levels in mainstream wastewater. / Deammonifikation är en välanvänd teknik för rening av sidoströmmar med höga ammoniumkoncentrationer vid relativt hög temperatur, som till exempel rejektvatten från avvattning av rötslam eller industriellt avloppsvatten. Deammonifikationsprocessen har lägre driftkostnad än konventionella reningsprocesser, förbrukar mindre energi samt möjliggör högre biogasproduktion samtidigt som processen är enkel att implementera. Reningstekniken har dock ännu inte tillämpats i fullskala för rening av huvudströmmen på grund av den höga C/N-kvoten och de låga vattentemperaturerna i kommunalt avloppsvatten samt behovet av efterbehandling. Detta anses ha en negativ inverkan på anammoxbakteriernas tillväxthastighet och funktion vilket påverkar bakteriegruppens beteende i processen. Syftet med detta examensarbete var att utvärdera om det är praktiskt genomförbart att använda deammonifikation för att rena kväve från kommunalt avloppsvatten, vilket följdes upp genom att studera bakterieaktiviteten i en pilotskalereaktor. De involverade bakteriegrupperna (AOB, NOB, heterotrofer och denitrifierare) övervakades genom att mäta den mikrobiella aktiviteten varje vecka med hjälp av batch-tester. Resultaten användes till att utvärdera olika driftstrategier och deras effekt genom att följa förändringarna i mikrobiell aktivitet hos de konkurrerande bakteriegrupperna. Studien genomfördes i Stockholm under sex månader i en enstegs-IFAS-pilotskalereaktor (integrerad process med biofilm på fast bärarmaterial och aktivslam) som matades med kommunalt avloppsvatten som förbehandlats i en UASB-reaktor. De olika driftstrategierna omfattade olika temperaturer, luftningsstrategier, syrekoncentrationer, slamåldrar och hydrauliska uppehållstider. Syftet med driftstrategierna var att främja AOB- och anammoxbakteriers tillväxt för att i framtida studier kunna erhålla en förbättrad deammonifikationsprocess. Syftet i denna studie var dock i första hand att förbättra den bakteriella konkurrensen och göra den lättare att mäta, inte att uppnå bästa möjliga kväverening. Den driftstrategi som gav bäst resultat i denna studie innebar att hålla en syrehalt på 1,5 mg/l med 10 minuter luftning följt av 20 minuter utan luftning vilket säkerställde en normal kväveavskiljning och samtidigt möjliggjorde övervakning av samtliga fyra bakteriegrupper. Totalkväveavskiljningen var över 50 % och ammoniumavskiljningen över 95 % medan kvävereningsaktiviteten ökade till 30 g N/m3-d och systemet hade en övergripande effektivitet på 75 %. Studien visade att under rätt förutsättningar kan de nödvändiga bakteriegrupperna selekteras fram och deammonifikation av kommunalt avloppsvatten kan utföras på ett framgångsrikt sätt.

Protecting the quality and quantity of our water resources requires advanced treatment technologies capable of removing nutrients from wastewater. This research work investigated the capability of one such technology, a hollow-fiber membrane-aerated biofilm reactor (HFMBR), to achieve completely autotrophic nitrogen removal from a wastewater with high nitrogen content. Because the extent of oxygenation is a key parameter for controlling the metabolic processes that occur in a wastewater treatment system, the first part of the research investigated oxygen transfer characteristics of the HFMBR in clean water conditions and with actively growing biofilm. A mechanistic model for oxygen concentration and flux as a function of length along the non-porous membrane fibers that comprise the HFMBR was developed based on material properties and physical dimensions. This model reflects the diffusion mechanism of non-porous membranes; namely that oxygen follows a sorption-dissolution-diffusion mechanism. This is in contrast to microporous membranes in which oxygen is in the gas phase in the fiber pores up to the membrane surface, resulting in higher biofilm pore liquid dissolved oxygen concentrations. Compared to offgas oxygen analysis from the HFMBR while in operation with biofilm growing, the model overpredicted mass transfer by a factor of approximately 1.3. This was in contrast to empirical mass transfer coefficient-based methods, which were determined using either bulk aqueous phase dissolved oxygen (DO) concentration or the DO concentration at the membrane-liquid interface, measured with oxygen microsensors. The mass transfer coefficient determined with the DO measured at the interface was the best predictor of actual oxygen transfer under biofilm conditions, while the bulk liquid coefficient underpredicted by a factor of 3. The mechanistic model exhibited sensitivity to parameters such as the initial lumen oxygen concentration (at the entry to the fiber) and the diffusion coefficient and partitioning coefficients of oxygen in the silicone membrane material. The mechanistic model has several advantages over empirical-based methods. Namely, it does not require experimental determination of KL, it is relatively simple to solve without the use of advanced mathematical software, and it is based upon selection of the membrane-biofilm interfacial DO concentration. The last of these is of particular importance when designing and operating HFMBR systems with redox (aerobic/anoxic/anaerobic) stratification, because the DO concentration will determine the nature of the microenvironments, the microorganisms present, and the metabolisms that occur. During the second phase of the research, the coupling of two autotrophic metabolisms, partial nitrification to nitrite (nitritation) and anaerobic ammonium oxidation, was demonstrated in a single HFMBR. The system successfully treated a high-strength nitrogen wastewater intended to mimic a urine stream from such sources as extended space missions. For the last 250 days of operation, operating with an average oxygen to ammonia flux (J_O₂/J_NH₄⁺) of 3.0 resulted in an average nitrogen removal of 74%, with no external organic carbon added. Control of nitrite-oxidizing bacteria (NOB) presented a challenge that was addressed by maintaining the J_O₂/J_NH₄⁺ below the stoichiometric threshold for complete nitrification to nitrate (4.57 g O₂ / g NH₄⁺). The DO-limiting condition resulted in formation of harmful gaseous emissions of nitrogen oxides (NO, N2O), which could not be prevented by short-term control strategies. Controlling JO2/JNH4+ prevented NOB proliferation long enough to allow an anaerobic ammoniaoxidizing bacteria (AnaerAOB) population to develop and be retained for >250 days. Addition of a supplemental nutrient solution may have contributed to the growth of AnaerAOB by overcoming a possible micronutrient deficiency. Disappearance of the gaseous nitrogen oxide emissions coincided with the onset of anaerobic ammonium oxidation, demonstrating a benefit of coupling these two autotrophic metabolisms in one reactor. Obvious differences in biofilm density were evident across the biofilm depth, with a region of low density in the middle of the biofilm, suggesting that low cell density or exocellular polymeric substances were primarily present in this region, Microbial community analysis using fluorescence in situ hybridization (FISH) did not reveal consistent trends with respect to length along the fibers, but radial stratification of aerobic ammonia-oxidizing bacteria (AerAOB), NOB, and AnaerAOB were visible in biofilm section samples. AerAOB were largely found in the first 25% of the biofilm near the membrane, AnaerAOB were found in the outer 30%, and NOB were found most often in the mid-depth region of the biofilm. This community structure demonstrates the importance of oxygen availability as a determinant of how microbial groups spatially distribute within an HFMBR biofilm. The combination of these two aspects of the research, predictive oxygen transfer capability and the effect of oxygen control on performance and populations, provides a foundation for future application of HFMBR technology to a broad range of wastewaters and treatment scenarios. / Ph. D.

Thesis (PhD (Chemical Engineering))--Cape Peninsula University of Technology, 2019 / Simultaneous nitrification and aerobic denitrification (SNaD) is a preferred method for single stage total nitrogen (TN) removal, which was recently proposed to improve wastewater treatment plant design. However, SNaD processes are prone to inhibition by toxicant loading with free cyanide (CN-) possessing the highest inhibitory effect on such processes, rendering these processes ineffective. Despite the best efforts of regulators to limit toxicant disposal into municipal wastewater sewage systems (MWSSs), free cyanide (CN-) still enters MWSSs through various pathways; hence, it has been suggested that CN- resistant or tolerant microorganisms be utilized for processes such as SNaD. To mitigate toxicant loading, organisms in SNaD have been observed to adopt a multiphase growth strategy to sequentially degrade CN- during primary growth and subsequently degrade TN during the secondary growth phase. However, CN- degrading microorganisms are not widely used for SNaD in MWSSs due to the inadequate application of suitable microorganisms (Chromobacterium violaceum, Pseudomonas aeruginosa, Thiobacillus denitrificans, Rhodospirillum palustris, Klebsiella pneumoniae, and Alcaligenes faecalis) commonly used in single-stage SNaD. The use of CN- degrading or resistant microorganisms for SNaD is a cost-effective method compared to the use of other methods of CN- removal prior to TN removal, as they involve multi-stage systems (as currently observed in MWSSs). The use of CN- degrading microorganisms, particularly when used as a consortium, presents a promising and sustainable resolution to mitigate inhibitory effects of CN- in SNaD. However, SNaD is known to be completely inhibited by CN- thus it is imperative to also study some thermodynamic parameters of SNaD under high CN- conditions to see the feasibility of the process. The Gibbs free energy is significant to understand the feasibility of SNaD, it is also vital to study Gibbs free energy to determine whether or not the biological reaction is plausible. The relationship between the rate of nitrification and Gibbs free energy was also investigated. The attained results showed that up to 37.55 mg CN-/L did not have an effect on SNaD. The consortia degraded CN- and achieved SNaD, with degradation efficiency of 92.9 and 97.7% while the degradation rate of 0.0234 and 0.139 mg/L/hr for ammonium-nitrogen (NH4-N) and CN- respectively. Moreover, all the free Gibbs energy was describing the individual processes were found to be negative, with the lowest Gibbs free energy being -756.4 and -1830.9 Kcal/mol for nitritation and nitratation in the first 48 h of the biological, reaction respectively. Additionally, a linear relationship between the rate of NH4-N and nitrite-nitrogen (NO2-N) degradation with their respective Gibbs free energy was observed. Linear model was also used to predict the relationship between NH4-N, NO2-N degradation and Gibbs free energy. These results obtained showed a good correlation between the models and the experimental data with correlation efficiency being 0.94 and 0.93 for nitritation, and nitratation, respectively. From the results found it can be deduced that SNaD is plausible under high cyanide conditions when cyanide degrading or tolerant microorganisms are employed. This can be a sustainable solution to SNaD inhibition by CN- compounds during wastewater treatment. Furthermore, a single strain was purified from the consortium and identified as Acinetobacter courvalinii. This bacterial strain was found to be able to perform sequential CN- degradation, and SNaD; an ability associated with multiphase growth strategy of the microorganism when provided with multiple nitrogenous sources, i.e. CN- and TN. The effect of CN- on nitrification and aerobic denitrification including enzyme expression, activity and protein functionality of Acinetobacter courvalinii was investigated. It was found that CN- concentration of up to 5.8 mg CN-/L did not affect the growth of Acinetobacter courvalinii. In cultures whereby the A. courvalinii isolate was used, degradation rates of CN- and NH4-N were found to be 2.2 mg CN-/L/h and 0.40 mg NH4-N/L/h, respectively. Moreover, the effect of CN- on NH4-N, nitrate-nitrogen (NO3-N) and NO2-N oxidizing enzymes was investigated, with findings indicating CN- did not affect the expression and activity of ammonia monooxygenase (AMO), but affected the activity of nitrate reductase (NaR) and nitrite reductase (NiR). Nevertheless, a slow decrease in NO2-N was observed after the addition of CN- thus confirming the activity of NaR and the activation of the denitrification pathway by the CN-. Moreover, five models’ (Monod, Moser, Rate law, Haldane, and Andrew’s model) ability to predict SNaD under CN- conditions, indicated that only Rate law, Haldane and Andrew’s models, were suited to predict both SNaD and CN- degradation. Due to low degradation rates of NH4-N and CN-, optimization of SNaD was essential. Therefore, response surface methodology was used to optimize the SNaD under CN- conditions. The physiological parameters that were considered for optimization were temperature and pH; with the result showing that the optimum for pH and temperature was 6.5 and 36.5oC respectively, with NH4-N and CN- degradation efficiency of 50 and 80.2%, respectively. Furthermore, the degradation kinetics of NH4-N and CN- were also studied under the optimum conditions in batch culture reactors, and the results showed that up to 70.6% and 97.3% of NH4-N and CN- were simultaneously degraded with degradation rates of 0.66 and 0.41 mg/L/h, respectively. The predictive ability of RSM was further compared with cybernetic models, and cybernetic models were found to better predict SNaD under CN- conditions. These results exhibited a promising solution in the management of inhibition effected of CN- towards SNaD at an industrial scale.

Partial Nitritation/Anammox process (deammonification process), by which occurs oxidation of ammonium to nitrogen gas by autotrophic bacteria in anaerobic conditions, considered to be cost-effective and environmentally friendly method of nitrogen removal. Present research work focuses on achieving a high nitrogen removal degree, thanks to Anammox bacteria, while providing the best performance of the ongoing process. Integrated fixed-film activated sludge (IFAS) reactor was supplied with the main stream of the wastewater after UASB reactor, characterized by low concentration of nitrogen and organic matter. The bacteria ability to accommodate, were tested in the biofilm and in the activated sludge, depending on the different stages in which the process were being conducted. Batch test, such as Specific Anammox Activity (SAA), Nitrate Uptake Rate (NUR) and Oxygen Uptake Rate (OUR), were used for the evaluation of activity of various groups of bacteria. On the basis of laboratory analysis verified the values obtained from the batch tests. It was determined that a high degree of nitrogen removal (92% of NH4-N) was achieved thanks to the dominant activity of the Anammox bacteria, with low participation of other groups of bacteria. It was also proved, that Anammox bacteria activity were overwhelming in the biofilm. Dominant role of Ammonium Oxidizing Bacteria (AOB) was associated with high activity of Anammox bacteria, which together satisfyingly out-competed Nitrite Oxidizing Bacteria (NOB) and heterotrophic bacteria. It has been shown that Anammox bacteria quickly adapt to the new conditions and they are able to assume a dominant role, even in the case of inoculation of the reactor with the sludge from SBR. This allows conclude, that in the case of operational problems, the reactor can be supplied from another source, in order not to inhibit the process.