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The subject of water scarcity and the rate of water consumption has become popular topics over the last few decades. It is possible that society may consume or contaminate much of the remaining readily available water if there is not a paradigm shift. This deep rooted concern has prompted investigations to identify alternative water use and treatment methods. Within this report, information is presented from the use of innovative water harvesting and on-site sewage treatment and disposal systems (OSTDS) at Florida’s Showcase Green Envirohome (FSGE.net), while also addressing low impact development (LID) practices. FSGE is a residential home that demonstrates methods that use less water and reduce pollution. Population increases have more than just an effect on the volume of water demanded. Adverse impacts on surface and groundwater quality are partially attributed to current design and operation of OSTDS. Nutrient loading from wastewater treatment systems may be a concern where numerous OSTDS are located within nutrient sensitive environments. Groundwater nitrate concentrations have been shown to exceed drinking water standards by factors of three or greater surrounding soil adsorption systems (Postma et al., 1992, Katz, 2010). As a contribution to efforts to reduce water use and improve water quality, this study investigates the viability and effectiveness of a residential integrated stormwater, graywater, and wastewater treatment system (ISGWTS) installed and operating for over a year at FSGE. ii Within this report is a continuation of results published previously that consisted of preCertificate of Occupancy (pre-CO) data and an optimization model at the Florida’s Showcase Green Envirohome (FSGE) in Indialantic, Florida (Rivera, 2010). This current report contains 12 months of post-CO data, along with data from bench scale models of the on-site septic treatment and disposal system (OSTDS). There are two main objectives of the study. The first objective is to quantify the performance of the passive treatment Bold & GoldTM reactive filter bed (FDOH classified “innovative system”) for nutrient removal. The second objective was to monitor the water quality of the combined graywater/stormwater cistern for non-potable use and assess the components (green roof, gutters, graywater piping). The performance of the passive innovative system is compared to past studies. Also a bench scale model that is constructed at the University of Central Florida (UCF) Stormwater Management Academy Research and Testing Lab (SMART Lab) is operated to provide data for two different retention times. Complex physical, biological, and chemical theories are applied to the analysis of wastewater treatment performance. The data from the OSTDS and stormwater/graywater cistern are assessed using statistical methods. The results of the OSTDS are compared to FDOH regulatory requirements for “Secondary Treatment Standards”, and “Advanced Secondary Treatment Standards” with promising results. The bench scale results verify that both nitrogen and phosphorus removal are occurring within the filter media and most likely the removals are due to iii biological activity as well as physiochemical sorption. The flow into the OSTDS has been reduced with the use of separate gray water system to only 29 gallons per person per day (gpcd). After the FSGE certificate of occupancy and for one year using the Bold & Gold Biosorption Activated Media (BAM), the TSS, BOD5, and CBOD5 are below the required 10 mg/L for the FDOH classified Advanced Secondary Treatment Systems. The effluent for the conventional drain field TSS, BOD5, and CBOD5 are above 10 mg/L (29.6, 35.7, and 29.0 mg/L). The effluent total nitrogen and total phosphorus for the innovative system are 29.7 mg/L and 4.1 mg/L, which are not low enough for the 20 mg/L nitrogen requirements, but are below the 10 mg/L phosphorus requirements. The conventional drain field has an effluent total nitrogen concentration of 70.1 mg/L and an effluent total phosphorus concentration of 10.6 mg/L, which both fail to meet FDOH Advanced Secondary Treatment requirements. The high nitrogen in the effluent can be attributed to high influent concentrations (about 3 times the average at about 150 mg/L). Longer residence times are shown to produce a removal greater than 90%. Also, nitrate average levels were below the 10 mg/L standard. The combined stormwater/graywater cistern is analyzed against irrigation standards. The graywater is filtered and disinfected with ozone to provide safe water for reuse. Nutrient concentrations are measured to compare with regulatory standards. For irrigation standards, salinity in the form of sodium, calcium, and magnesium are measured. Although high sodium adsorption ratio (SAR) and electrical conductivity (EC) values were recorded, their adverse iv impact on the vegetation has not been observed. . The only observed effect within the home to date is scale formation in the toilet. The use of potable water in FSGE is reduced to 41 gpcd using the integrated stormwater and graywater system. A minor volume of backup artesian well water was added to the cistern during the one year home occupancy phase. Based on less use of potable water and at the current potable water cost rate, the integrated stormwater and graywater system at FSGE will save the typical homeowner about $215 per year. If irrigation were used more often from the cistern, the cost savings in reduced potable water used for irrigation would increase the savings. The treatment cost for B&G BAM over a 40 year period of time based on a flow of 29 gpcd (as measured at FSGE) and for 4 persons is $2.07 per thousand gallons treated. The yearly cost of treatment is about $87.65. There is a reduction in potable water use estimated at 64% of the sewage flow (or 18.5 gpcd) which equates to about 27 thousand gallons in one year. The current average cost of potable water is $4.40 per thousand gallons. Based on reduced potable water usage, the savings per year are about $118.84. Thus the yearly savings in potable water cost ($118.84) offsets the cost of OSTDS treatment at FSGE for nutrient control ($87.65) using the data collected at FSGE. This comparison does not include the inflation cost of water over time. There is also an environmental preservation intangible cost (not quantifiable from this study) from reduced surface runoff and reduced pollutant discharges.

M. Tech. (Department of Biotechnology, Faculty of Applied and Computer Sciences) Vaal University of Technology. / Pollution of aquatic systems by wastewater containing pathogens, heavy metals and high concentrations of nutrients is of great concern due the ecological risks they impose. The toxic effects of metals may occur even at low concentrations because of potential bio magnification in the food chain. Excessive nutrients cause algal blooms which depletes oxygen and prevents sunlight from penetrating into the water, thereby killing fish and other aquatic organisms. This study investigated the pollutant removal efficiency of a riparian wetland located in Sebokeng, Emfuleni local municipality, South Africa. The study was carried out to assess the water quality of a wetland located downstream of the Sebokeng wastewater treatment plant by monitoring and analysing the physico-chemical parameters which included pH, temperature, electrical conductivity, nutrient levels (nitrates, phosphates, nitrites) and heavy metals. The water samples were collected from the effluent discharge of the treatment plant, upstream and downstream of the wetland. Plant uptake of heavy metals in a riparian wetland, nitrification as well as denitrification processes have been historically recorded as the main processes that contribute to the high removal of pollutants in a wetland. The contaminant concentrations of the influent and the effluent were used to estimate the wetland efficiency in improving the water quality that passes through it and its potential effects on improving the quality of irrigation waters. The heavy metals of interest included Al, Cd, Cr, Cu, Fe, Pb, Mn and Zn. Most heavy metals within the wetland occurred at low concentrations (lower than detectable limits and within the discharge limits for irrigation purposes). The results indicate that the average removal efficiencies for Electrical Conductivity (EC), Total coliforms (TC), E. coli, BOD5, COD, TSS, carbonate hardness, aluminium, iron, manganese, copper, nitrite, nitrate, sulfate and ortho-phosphate were 43 %, 51%, 85%, 60%, 61%, 61%, 21%, 67%, 52%, 51%, 83%, 56%, 89%, 49% and 54% respectively. The study showed that this wetland can provide up to 89% removal efficiency of pollutants. Of particular significance was the high pathogen and nutrient removal efficiency. A t-test was performed in order to determine the statistical significance of the wetland pollutant removal efficiencies. All p-values calculated were well below 0.05 and the removal efficiencies are therefore considered statistically significant. For this particular ecosystem the findings show that there is no great concern about metal pollution since most of the metals tested for were below the minimum limit for irrigation stipulated by the South African water regulation department (DWAF 1996a). Therefore, the wetland effluent water qualifies for both agriculture and landscape irrigation. Future considerations in choosing to use wetlands as a polishing facility for wastewater treatment systems are highlighted in the study.

In this study, we aim to employ Chlorella vulgaris algae for removal of nutrients in wastewater and collect the produced algae by ferrate after treatment. The growth of algae was conducted in F/2 synthetic medium and in actual domestic wastewater. The removals of nitrogen and phosphorous by algae were then investigated for low and high nutrient concentrations using wastewater after biological treatment in both batch and continuous experiments. Results showed that specific growth rates in the exponential phase were 0.23 and 0.35 day-1 for F/2 medium and domestic wastewater, respectively, proving the suitability of wastewater for algae growth. The removal efficiency of ammonia, nitrate, and phosphate were 89 - 93, 64 - 76, and 69 – 88%, respectively. In the algae collection test, pH 8 is the optimal pH to remove algae and ferrate had higher algae removal ability than alum under each optimal condition with removal efficiency of 84 - 97% at dosage of 12 mg Fe/L. These results suggest that microalgae is a potential alternative for removing of nutrients in wastewater treatment due to the high uptake capacity of nitrogen and phosphorous and the effective collection of algae after treatment by ferrate. / Mục tiêu của nghiên cứu này là đánh giá hiệu quả xử lý chất dinh dưỡng bằng tảo Chlorella vulgaris trong môi trường nước thải sinh hoạt, thông qua khả năng xử lý N và P từ nguồn nước khi tảo tăng trưởng và khả năng keo tụ để thu hồi tảo bằng ferrate. Tốc độ tăng trưởng đặc thù µ trong môi trường F/2 và nước thải sinh hoạt lần lượt là 0,23 ngày-1 và 0,35 ngày-1. Hiệu suất xử lý ammoni, nitrát và phốt phát- lần lượt đạt 89 - 93%, 64 - 76% và 69 - 88%. Kết quả thí nghiệm keo tụ thu hồi tảo cho thấy pH = 8 là thích hợp nhất để loại bỏ tảo bằng ferrate và việc sử dụng ferrate cho hiệu quả tách tảo tốt hơn phèn nhôm với lượng sử dụng ít hơn. Ở hàm lượng 12 mgFe/L, hiệu quả tách tảo đạt cao nhất từ 84 - 97%. Nghiên cứu cho thấy tiềm năng thay thế công nghệ sinh học truyền thống bằng công nghệ vi tảo trong loại bỏ các chất dinh dưỡng và khả năng thu hồi tảo hiệu quả bằng cách sử dụng ferrate.

Mariculture has currently brought greatly valuable products in many fields simultaneously released a large amount of wastewater contributing to water pollutions on account of its organic and inorganic constituents. Nowadays, with the development of environmental engineering, more and more approaches, especially friendly-environmental and highly effective wastewater biological methods, are being applied to tackle pollutions and minimize adverse effects of treatments to reach the sustainable development. This report focuses on the study of proliferation combined with elimination of polluting substances of marine algae species Tetraselmis suiscica, Tetraselmis sp., Platymonas sp. in aquaculture wastewater sampled from Can Gio District, Ho Chi Minh City, Vietnam with levels of concentration during 14 days under normal marine algae culture conditions, and compared to that in Daigo’s IMK media. The results shown that, the algae species all grew rapidly simultaneously gave high nutrients removal yields (COD, N, P) and created a considerable amount of biomass within a short period of culture. Particularly, Platomonas sp. and Tetraselmis suiscica could proliferate aswell as give high treatment yields of organic substances (COD), PO43-, NO3-, NH4+ and Total Nitrogen in concentrated wastewater. To sum up, this study showed the potential of using microalgae to reduce COD, nitrogen and phosphorus in mariculture wastewater. / Ngành nuôi trồng thủy hải sản trong những nằm gần đây đã mang lại nhiều sản phẩm có giá trị trong nhiều lĩnh vực đồng thời thải ra một lượng lớn nước thải gây ô nhiễm nguồn nước bởi các thành phần vô cơ và hữu cơ có trong nước thải. Ngày nay, với sự phát triển của kỹ thuật môi trường, ngày càng nhiều cách tiếp cận, đặc biệt là các phương pháp sinh học hiệu quả cao và thân thiện với môi trường đang được ứng dụng để xử lý ô nhiễm và giảm thiểu hậu quả bất lợi sau xử lý, nhằm hướng tới sự phát triển bền vững. Bài báo cáo tập trung nghiên cứu khả năng sinh trưởng và phát triển của ba loài vi tảo biển Tetraselmis suiscica, Tetraselmis sp., Platymonas sp. kết hợp với việc loại bỏ các hợp chất gây ô nhiễm có trong nước thải từ ao nuôi tôm của huyện Cần Giờ, Việt Nam và so sánh đối chiếu với môi trường dinh dưỡng Daigo’s IMK trong 14 ngày nuôi trồng. Kết quả cho thấy những vi tảo sinh trưởng rất nhanh nhờ vào việc sử dụng các chất ô nhiễm trong nước thải, đặc biệt hiệu suất xử lý COD, PO43-, NO3-, NH4+ và nitơ tổng của Platomonas sp. và Tetraselmis suiscica rất cao thậm chí trong môi trường nước thải đậm đặc. Do đó, chúng tôi kết luận, vi tảo có tiềm năng rất lớn trong việc giảm nồng độ chất hữu cơ, phốt pho và nitơ trong nước thải nuôi trồng thủy hải sản.

Enhanced biological phosphorus removal (EBPR) was researched from the performance of a modified University of Cape Town (UCT), anaerobic-anoxic/nitrifying-aerobic process. The work focussed on high P influent where milk was compared to carbohydrates as exogenous added carbon and typical settled sewage. The results confirmed that at equal COD load in the influent (minimum COD:P (250:5) ratio for EBPR), milk always provided sufficient soluble substrate than the carbohydrate mix, but also improved the EBPR performance. The laboratory scale treated 10L/day where 2 parallel treatment trains for milk and an equivalent carbohydrate mix as supplement to compare and study the P sequestration from hypothesised P ligands in milk and easily assimilable carbon (AOM) after fermentation for biological P uptake. The aerobic bioreactors used submerged flat sheet membranes (AeMBR) to improve the effluent quality and reduce the suspended solid residues. The results suggested extra benefits from adding calcium chloride (CaCl2) (200 ml at 250 mM/day or 200 mg/L treated) to form P complexes both in the anaerobic and aerobic zones (100 ml CaCl2 250mM/zone/day). To complete P removal a calcium phosphate (CaPO4) further treatment stage (post membrane final effluent (F.E.)) was added for nucleation. The combination of, A2O-N, exogenous carbon and calcium addition improved the performance of the EBPR, and enabled the laboratory units to achieve less than the 1 mg/L P required by the EU Directive. The process was tested at higher than normal P loads (maximum 100 mg/L) (domestic wastewater influent 15 mg/L). Experiments with influent P load ≤ 50mg/L, with 1% milk as AOM were compared to the carbohydrate mix and could remove soluble P to less than 1mg/L above 97% and less than 2 mg/L more than 99% of the in the time respectively. With an influent P load of 60mg/L (maximum 100 mg/L), the soluble P in the F.E. with milk was below 5 mg/L and below 8 mg/L with carbohydrates mix. The results showed that most of the phosphorus was retained by the sludge during the anoxic-aerobic phases. The remaining phosphate in the F.E. was able to pass through AeMBR pore size (0.4 μm) and needed to be chelated by the nucleation process. The results indicated this A2O-N modifications achieved stable nutrient removal and also offered the potential for more sustainable phosphorus recovery. The EBPR without AOM was 25% less efficient compared to milk and never achieved the E.U standard of 1mg/L in final effluent. The flat sheet membrane always achieved a NTU final effluent below 1 and the TOC always greater than 90% removal or less than the EU 125 standard regardless of the feeding COD/P ratio.

Tendo em vista a crescente problemática quanto à eutrofização de corpos dágua em países em desenvolvimento, devido ao lançamento de esgoto mesmo que tratado em nível secundário, o processo de lodo ativado vem sendo estudo e aprimorado para efetuar a remoção conjunta de matéria orgânica, nitrogênio e o fósforo, nutrientes limitantes para ocorrência da eutrofização. Neste contexto, o presente trabalho pretende contribuir com informações quanto à remoção biológica de nutrientes de esgoto sanitário através de estudo em escala piloto em um sistema cíclico de lodo ativado. Este sistema, operado em regime de bateladas sequenciais, difere da configuração habitual, pois possui três compartimentos internos, zonas 1, 2 e 3 que apresentam condições anaeróbias/anóxicas, anóxicas e aeróbias respectivamente, além do retorno de lodo da zona 3 para zona 1 durante o período de reação, sob vazão de 20% da vazão afluente a unidade. Cada batelada possui duração de 4 horas, distribuídas em 4 etapas de 1h cada, sendo elas o enchimento com aeração, reação, sedimentação e descarga. Com essas características o sistema cíclico de lodo ativado do presente estudo, demonstrou no tratamento de esgoto sanitário, elevada eficiência na remoção de matéria orgânica, sempre acima de 90%, além da boa eficiência de remoção nitrogênio através do processo de nitrificação e desnitrificação, cuja concentração média de amônia e nitrato no efluente final foram respectivamente de 2,8 e 11,4 mgN.L-1 para idade de lodo de 25 dias e quando operado com 12 dias de idade, o efluente apresentou concentração de 6,6 e 12,4 mgN.L-1. Também foram determinadas via respirometria as taxas máximas de crescimento (n,max) para bactérias nitrificantes e nitratantes, os valores obtidos foram respectivos, de 0,45 d-1 e 0,37 d-1 para idade de lodo de 12 dias, resultados próximos a literatura. A remoção biológica de fósforo foi obtida com melhor resultado na segunda etapa, superando 95% de eficiência, produzindo efluente final com teor de fósforo total inferior a 0,5 mgP.L-1. / Given the growing problem regarding the eutrophication of water bodies in developing countries, due to discharge of sewage treated even at the secondary level, the activated sludge process has been enhanced to study and perform the joint removal of organic matter, nitrogen and phosphorus, the limiting nutrient for the occurrence of eutrophication. In this context, this work aims to contribute information for biological nutrient removal from wastewater by pilot scale study in a cyclic activated sludge system. This system operated in sequential batch system differs from typical configuration because it has three internal compartments, zones 1, 2 and 3 show that anaerobic / anoxic, aerobic and anoxic respectively, beyond the conditions of return sludge from zone 3 to zone 1 during the reaction, flow rate under 20% of the influent flow unit. Each batch has a duration of 4 hours, distributed into 4 stages each 1H, they aeration and filling, reaction, settling and discharge. With these characteristics the cyclic activated sludge system of the present study showed for the treatment of sewage, high efficiency in the removal of organic matter, always above 90%, besides the good efficiency of nitrogen removal by nitrification and denitrification, which average concentration of ammonia and nitrate in the final effluent were respectively 2.8 and 11.4 mgN.L-1 for sludge age of 25 days, when operated at 12 days of age, the effluent showed a concentration of 6.6 to 12 4 mgN.L-1. Were also determined via respirometry maximum growth rates (n, max) for nitrifying bacteria and nitratantes, the respective value obtained were, 0.45 d-1 and 0.37 d-1 for sludge age of 12 days, results Nearby literature. Biological phosphorus removal was obtained with better results in the second stage, surpassing 95% efficiency, producing the final content of the effluent below 0.5 mgP.L-1 total phosphorus.

Tendo em vista a crescente problemática quanto à eutrofização de corpos dágua em países em desenvolvimento, devido ao lançamento de esgoto mesmo que tratado em nível secundário, o processo de lodo ativado vem sendo estudo e aprimorado para efetuar a remoção conjunta de matéria orgânica, nitrogênio e o fósforo, nutrientes limitantes para ocorrência da eutrofização. Neste contexto, o presente trabalho pretende contribuir com informações quanto à remoção biológica de nutrientes de esgoto sanitário através de estudo em escala piloto em um sistema cíclico de lodo ativado. Este sistema, operado em regime de bateladas sequenciais, difere da configuração habitual, pois possui três compartimentos internos, zonas 1, 2 e 3 que apresentam condições anaeróbias/anóxicas, anóxicas e aeróbias respectivamente, além do retorno de lodo da zona 3 para zona 1 durante o período de reação, sob vazão de 20% da vazão afluente a unidade. Cada batelada possui duração de 4 horas, distribuídas em 4 etapas de 1h cada, sendo elas o enchimento com aeração, reação, sedimentação e descarga. Com essas características o sistema cíclico de lodo ativado do presente estudo, demonstrou no tratamento de esgoto sanitário, elevada eficiência na remoção de matéria orgânica, sempre acima de 90%, além da boa eficiência de remoção nitrogênio através do processo de nitrificação e desnitrificação, cuja concentração média de amônia e nitrato no efluente final foram respectivamente de 2,8 e 11,4 mgN.L-1 para idade de lodo de 25 dias e quando operado com 12 dias de idade, o efluente apresentou concentração de 6,6 e 12,4 mgN.L-1. Também foram determinadas via respirometria as taxas máximas de crescimento (n,max) para bactérias nitrificantes e nitratantes, os valores obtidos foram respectivos, de 0,45 d-1 e 0,37 d-1 para idade de lodo de 12 dias, resultados próximos a literatura. A remoção biológica de fósforo foi obtida com melhor resultado na segunda etapa, superando 95% de eficiência, produzindo efluente final com teor de fósforo total inferior a 0,5 mgP.L-1. / Given the growing problem regarding the eutrophication of water bodies in developing countries, due to discharge of sewage treated even at the secondary level, the activated sludge process has been enhanced to study and perform the joint removal of organic matter, nitrogen and phosphorus, the limiting nutrient for the occurrence of eutrophication. In this context, this work aims to contribute information for biological nutrient removal from wastewater by pilot scale study in a cyclic activated sludge system. This system operated in sequential batch system differs from typical configuration because it has three internal compartments, zones 1, 2 and 3 show that anaerobic / anoxic, aerobic and anoxic respectively, beyond the conditions of return sludge from zone 3 to zone 1 during the reaction, flow rate under 20% of the influent flow unit. Each batch has a duration of 4 hours, distributed into 4 stages each 1H, they aeration and filling, reaction, settling and discharge. With these characteristics the cyclic activated sludge system of the present study showed for the treatment of sewage, high efficiency in the removal of organic matter, always above 90%, besides the good efficiency of nitrogen removal by nitrification and denitrification, which average concentration of ammonia and nitrate in the final effluent were respectively 2.8 and 11.4 mgN.L-1 for sludge age of 25 days, when operated at 12 days of age, the effluent showed a concentration of 6.6 to 12 4 mgN.L-1. Were also determined via respirometry maximum growth rates (n, max) for nitrifying bacteria and nitratantes, the respective value obtained were, 0.45 d-1 and 0.37 d-1 for sludge age of 12 days, results Nearby literature. Biological phosphorus removal was obtained with better results in the second stage, surpassing 95% efficiency, producing the final content of the effluent below 0.5 mgP.L-1 total phosphorus.

The microbial aggregates (flocs) formed during secondary biological treatment of wastewater shield microbes from exposure to ultraviolet (UV) light, and decrease the efficiency of disinfection, causing the tailing phenomena. This thesis investigates whether the formation of compact cores within flocs induces higher levels of UV resistance. Moreover, it investigates the effect of secondary treatment conditions on the physicochemical properties of flocs’, effluent quality, and UV disinfection performance. Compact cores were isolated from the flocs using hydrodynamic shearing. The UV dose response curves (DRC) were constructed for flocs and cores, and the 53-63 μm cores showed 0.5 log less disinfectability, compared to flocs of similar size. Based on a structural model developed for the UV disinfection of flocs, floc disinfection kinetics was sensitive to the core’s relative volume, their density, and viability. The UV disinfection and floc properties of a conventional activated sludge (CAS) system, and a biological nutrient removal (BNR-UCT) system, including both biological nitrogen and phosphorus removal, was compared. The 32-53 μm flocs and the final effluent from the BNR-UCT reactor showed 0.5 log and 1 log improvement in UV disinfectability, respectively, compared to those from the CAS reactor. The BNR-UCT flocs were more irregular in structure, and accumulated polyphosphates through enhanced biological phosphorus removal. Polyphosphates were found to be capable of producing hydroxyl radicals under UV irradiation, causing the photoreactive disinfection of microorganisms embedded within the BNR-UCT flocs, accelerating their UV disinfection. Comparing the UV disinfection performance and floc properties at various operating conditions showed that increasing the operating temperature from 12 ºC to 22 ºC, improved the UV disinfection of effluent by 0.5 log. P-Starved condition, i.e. COD:N:P of 100:10:0.03, decreased the average floc size and sphericity, both by 50%. Despite the higher effluent turbidity of the P-Starved reactor, the final effluent’s UV disinfection improved by at least 1 log compared to the P-Normal and P-Limited conditions. The improvement in the floc and effluent disinfectability were accompanied by a decrease in floc sphericity and a decrease in the number of larger flocs in the effluent, respectively.

The microbial aggregates (flocs) formed during secondary biological treatment of wastewater shield microbes from exposure to ultraviolet (UV) light, and decrease the efficiency of disinfection, causing the tailing phenomena. This thesis investigates whether the formation of compact cores within flocs induces higher levels of UV resistance. Moreover, it investigates the effect of secondary treatment conditions on the physicochemical properties of flocs’, effluent quality, and UV disinfection performance. Compact cores were isolated from the flocs using hydrodynamic shearing. The UV dose response curves (DRC) were constructed for flocs and cores, and the 53-63 μm cores showed 0.5 log less disinfectability, compared to flocs of similar size. Based on a structural model developed for the UV disinfection of flocs, floc disinfection kinetics was sensitive to the core’s relative volume, their density, and viability. The UV disinfection and floc properties of a conventional activated sludge (CAS) system, and a biological nutrient removal (BNR-UCT) system, including both biological nitrogen and phosphorus removal, was compared. The 32-53 μm flocs and the final effluent from the BNR-UCT reactor showed 0.5 log and 1 log improvement in UV disinfectability, respectively, compared to those from the CAS reactor. The BNR-UCT flocs were more irregular in structure, and accumulated polyphosphates through enhanced biological phosphorus removal. Polyphosphates were found to be capable of producing hydroxyl radicals under UV irradiation, causing the photoreactive disinfection of microorganisms embedded within the BNR-UCT flocs, accelerating their UV disinfection. Comparing the UV disinfection performance and floc properties at various operating conditions showed that increasing the operating temperature from 12 ºC to 22 ºC, improved the UV disinfection of effluent by 0.5 log. P-Starved condition, i.e. COD:N:P of 100:10:0.03, decreased the average floc size and sphericity, both by 50%. Despite the higher effluent turbidity of the P-Starved reactor, the final effluent’s UV disinfection improved by at least 1 log compared to the P-Normal and P-Limited conditions. The improvement in the floc and effluent disinfectability were accompanied by a decrease in floc sphericity and a decrease in the number of larger flocs in the effluent, respectively.