Wastewater microbial flocs can protect microorganisms from inactivation by UV light. This effect is detected as tailing at high UV doses in the UV dose response curve. A double-layer structure composed of an inner compact core surrounded by a loose outer layer was proposed by earlier studies to describe UV resistance of microbial flocs. Due to limited oxygen diffusion into the compact cores, the UV inactivation of compact cores and microbial flocs under anaerobic conditions needed to be addressed. The UV disinfection kinetics under anaerobic culturing condition was nearly identical to that of the aerobic study. Moreover, the role of iron concentration on the differences in the UV inactivation kinetics of flocs and cores was assessed. The increase in UV absorbance of floc material due to iron addition could dominate the UV disinfection kinetics of flocs and cores such that they exhibited similar UV disinfection kinetics.

Wastewater microbial flocs can protect microorganisms from inactivation by UV light. This effect is detected as tailing at high UV doses in the UV dose response curve. A double-layer structure composed of an inner compact core surrounded by a loose outer layer was proposed by earlier studies to describe UV resistance of microbial flocs. Due to limited oxygen diffusion into the compact cores, the UV inactivation of compact cores and microbial flocs under anaerobic conditions needed to be addressed. The UV disinfection kinetics under anaerobic culturing condition was nearly identical to that of the aerobic study. Moreover, the role of iron concentration on the differences in the UV inactivation kinetics of flocs and cores was assessed. The increase in UV absorbance of floc material due to iron addition could dominate the UV disinfection kinetics of flocs and cores such that they exhibited similar UV disinfection kinetics.

Overfishing of natural fisheries is a global issue that is becoming more urgent as the human population increases exponentially. According to the Food and Agriculture Organization of the United Nations, over 70% of the world's seafood species are fully exploited or depleted. This high demand for seafood protein is not going away; and, in fact, an astonishing one out of five people in this world depend on this source of protein. Traditional aquaculture practices use pond and flow-through systems which are often responsible for discharging pollutants into the environment. Furthermore, aquacultural feeds often contain high levels of fish protein, so the demand on wild fisheries is not completely eased. Even though traditional aquaculture has these drawbacks, there is a significant movement towards more sustainable practices. For example, implementing recirculating aquaculture systems (RAS) maximizes the reuse of culture water which decreases water demand and minimizes the levels of pollutants being discharged to the environment. And, alternative proteins (e.g., soy bean) are replacing the fish and seafood proteins in aquaculture diets. Accordingly, the research described in this dissertation focused on maximizing the reuse of freshwater fish effluent to culture marine shrimp. More specifically, by using suspended-growth biological reactors to treat a tilapia effluent waste stream and to generate microbial flocs that could be used to support shrimp culture. This RAS technology will decrease water consumption by increasing the amount of recycled water and will also improve effluent water quality. The biomass generated in the bioreactors could be used to feed shrimp with an alternative source of protein. Treating fish effluent to be reused to culture shrimp while producing this alternative feed, could significantly decrease operational costs and make these operations more sustainable. Understanding which ions are critical for the survival and normal growth of marine shrimp in freshwater effluents is essential. It is also very important to understand how to convert an effluent's organic matter into food for shrimp. Results from studies revealed that the marine shrimp, Litopenaeus vannamei, can be raised in freshwater effluent when supplemented with specific ions and wet microbial flocs fed directly to shrimp can enhance growth in shrimp fed a restricted ration of commercial feed. The treatability of the tilapia effluent using suspended-growth, biological reactors and nutritional analysis of the generated biomass were also reported. Carbon supplementation enhanced reactor performance and microbial floc generation. These microbial flocs also proved to be a superior feed ingredient when dried and incorporated into a pellet feed. / Ph. D.

Submitted by (edna.saturno@ufrpe.br) on 2017-02-13T14:16:14Z No. of bitstreams: 1 Freddy Vogeley de Carvalho.pdf: 463787 bytes, checksum: b80fbb83db5f99c4b734647939d38607 (MD5) / Made available in DSpace on 2017-02-13T14:16:14Z (GMT). No. of bitstreams: 1 Freddy Vogeley de Carvalho.pdf: 463787 bytes, checksum: b80fbb83db5f99c4b734647939d38607 (MD5) Previous issue date: 2010-02-12 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / In the present study compared the growth performance of Litopenaeus vannamei and Farfantepenaeus subtilis in nursery heterotrophic system. The experimental design consisted of two treatments (L. vannamei and F. subtilis) with four replications. The cultivation was carried out during 52 days in tanks like "raceway" (0.9m2 and 300L), with initial stocking density of 222 shrimp/m2 and initial weight of 0.024g and 0.034g for L. vannamei and F. subtilis. The animals were fed a commercial ration (35% crude protein). The formation of heterotrophic environment was induced by adding organic fertilizer (molasses) to adjust the relationship Carbon:Nitrogen (20:1). The physical and chemical parameters of water quality showed no significant differences between treatments. The assessment of growth performance showed significant differences between the species with the highest growth (0.31g/week), higher mean final weight (2.31g) and better-feed conversion factor (0.70) for L. vannamei, compared to F. subtilis with a growth of 0.12g/week, final average weight of 0.88g and feed conversion factor of 1.09. However, F. subtilis had a higher survival (83.50%) than the L. vannamei (63.25%). Despite the best performance obtained by L. vannamei, the results indicate the potential for nursery F. subtilis in heterotrophic systems. / No presente estudo foi comparado o desempenho zootécnico de Litopenaeus vannamei e Farfantepenaeus subtilis em berçário de sistema heterotrófico. O desenho experimental foi constituído por dois tratamentos (L. vannamei e F. subtilis), com quatro repetições. O cultivo foi realizado durante 52 dias em tanques tipo “raceway” (0,9m2 e 300L), com densidade inicial de estocagem de 222 camarões/m2 e peso inicial de 0,024g e 0,034g para L. vannamei e F. subtilis, respectivamente. Os animais foram alimentados com ração comercial (35% proteína bruta). A formação do ambiente heterotrófico foi induzida através da adição de fertilizante orgânico (melaço) para ajuste da relação Carbono:Nitrogênio (20:1). As variáveis físicas e químicas de qualidade da água não apresentaram diferenças significativas entre os tratamentos. A avaliação do desempenho zootécnico apresentou diferenças significativas entre as espécies, com maior crescimento (0,31g/semana), maior peso médio final (2,31g) e melhor fator de conversão alimentar (0,70) para o L. vannamei, quando comparado ao F. subtilis que apresentou crescimento de 0,12g/semana, peso médio final de 0,88g e fator de conversão alimentar de 1,09. Entretanto, o F. subtilis obteve maior sobrevivência (83,50%) que o L. vannamei (63,25%). Apesar do melhor desempenho zootécnico obtido pelo L. vannamei, os resultados indicam potencial para o berçário do F. subtilis em sistemas heterotróficos.

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.