Chlorine is the most widely used disinfectant for drinking water treatment. Chlorine canreact with natural organic matter (NOM) in water sources resulting in the formation of potentially carcinogenic disinfection by-products (DBPs). The most common DBPs measured in chlorinated drinking water distribution systems are trihalomethanes (THMs) and haloacetic acids (HAAs). In 2005, the City of Kamloops, British Columbia upgraded the drinking water treatment system to ultrafiltration membrane treatment. The objective of this study was to determine the extent to which upgrades to a drinking water treatment system, specifically, implementation of an ultrafiltration treatment process, impacted DBP formation within a distribution system. This study used a two-phase research approach. Phase I of the study was a distribution system monitoring program that collected water samples and physical and chemical information using data loggers at five sampling sites within the distribution system. Phase II of the study used bench-scale simulations that modeled DBP formation using a flow-through reactor system, the material-specific simulated distribution system (MS-SDS), constructed of pipe material resurrected from the City of Kamloops distribution system. Phase I results suggested that implementation of the ultrafiltration treatment process and accompanying treatment system upgrade was not effective at reducing the concentration of DBPs delivered to consumers. Concentrations of THMs remained relatively constant at sampling sites, while concentrations of HAAs increased following implementation of the ultrafiltration treatment process. The increase in HAA formation was likely due to an increase in retention time of the water within the distribution system following implementation of the ultrafiltration treatment process, rather than due to the treatment process itself. The results of this study are consistent with previous work on South Thompson River water DBP precursors, which suggested that THM and HAA precursors of this source water are small and hydrophilic, and therefore cannot be removed by ultrafiltration processes. Phase II results showed that the MS-SDS was more representative of distribution system c onditions than traditional glass bottles to estimate DBP formation. It is recommended that the MS-SDS be used in parallel with a simultaneous distribution system monitoring program to estimate distribution system retention times from THM and HAA concentrations. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

An enthusiastic global campaign on intervention in water in the Lower Income Countries (LICs) was launched by the UN at the International Conference on Water and the Environment (ICEW), in Rio de Janerio, in January of 1992. In June of the same year, in Dublin, a plan of action was devised and a commitment to the water related goals highlighted in Rio de Janerio was made. Close to fifteen years on, there is little to show by way of success in the intended countries. Over 1.1 billion people in the LICs lack safe water. The direct impact of this is a higher risk of waterborne diseases. The waterborne diseases claim 42,000 lives every week in the LICs. By any standards this is a serious depletion of the human capital stock. Looked at in light of the fact that these countries still heavily rely on labour in production, amplifies the need to preserve health. The inherent danger posed by the poor quality water‐ as can be drawn from the above statistics‐ seems to suggest that improving the quality of water would go a long way in improving and preserving societal health in the LICs. By implication this would improve the productivity of the workers. Other benefits include cost mitigation, improved investor confidence as well as increased tourists’ confidence‐ all of which are vital for LICs’ growth prospects. It begs the question of why these countries have not improved their water quality. With specific reference made to Uganda, this research is bent on answering this question. In Uganda, there is consensus among scientists that the ground and open water sources are degraded to dangerous levels. Water quality parameters like turbidity, coliform count, and colour are all above the WHO minimum specifications for potable water and are on the rise in the country. This is indicative of water quality deterioration and it heightens the risk of waterborne diseases to the users. The waterborne burden of disease in Uganda is on the rise with a high fatality rate of 440 lives every week. The need to improve water quality in the country has been acknowledged. However, attempts to address the problem have only been undertaken on a small scale, most notable of these being the PuR home water treatment vii program. There is evidence in the country that the water quality would have apparent benefits. Strong correlations have been found between improved health in HIV patients and improved water quality in the country. In the economics of health, improving societal health inherently improves workers’ performance and productivity, leading to higher growth of the economy. There is an economic imperative therefore, as to why countries like Uganda should improve their water quality. In spite of this, even the country’s most urbanized setting‐ Kampala‐ lacks potable water. This study therefore investigates why, in a time when not only the global agenda is more supportive than ever and when the country’s water resources have been found to be risky to use, Uganda has not improved water quality. Kampala is used as the model district for this study. The district accounts for three quarters of users of treated water in the country. The problem is investigated by assessing the efficiency case of such a project (a water quality improving project) in the country; the methodology employed to this end is the Cost Benefit Analysis (CBA). The methodology compares the costs and benefits of a project, in monetary terms, in the same analysis, over its useful life. In the application of CBA one allows for the time value of money by using the discount rate to make the costs and benefits of the project occurring in different years comparable. In principle, the methodology is simple to apply‐ only that issues arise in the quantification of benefits and the determination of the discount rate. Benefits of the Kampala water quality, improving project include non‐market values and for this reason a non‐market valuation technique, the Contingent Valuation Method (CVM), was employed in their quantification. The CVM technique estimates the benefits by measuring the individuals’ willingness to pay for the improved scenario‐ in this case the scenario was one with a water quality‐improving project. The application of the CVM across many disciplines has invited a lot of criticism over the reliability of its estimates as a measure of value. A panel assembled by the North Oceanic and Atmospheric Administration (NOAA) to investigate the reliability of the CVM resolved that as long as the CVM was well conducted, the generated results would reliably predict non‐market values. The Kampala CVM, for the benefits’ quantification, was conducted with the NOAA guidelines in mind. The final value of the project’s benefits was the WTP predicted for the viii median respondent namely Ushs 385.07/= per cubic meter of water. The discount rate was deemed to be the social opportunity cost of capital in the country, viz 12 percent, this being that rate of return foregone by investing in another sector. The project’s costs were arrived at through liaison with water engineers and consulting past data from Uganda’s Water suppliers. From this, the project’s fixed costs were predicted to be Ushs 1451/= per cubic meter of water and the operation and maintenance costs predicted to be Ushs 591.7/= per cubic meter of water. The project’s useful life was deemed to be the average life of a Ugandan, namely 52 years; this choice reflecting the belief that the benefits would last over the users’ whole life. The results of the Kampala water quality‐improving project indicate that the project would not be feasible. It did not matter what discount rate one employed, the project’s operating and maintenance (OM) costs exceed the benefits. The results offer an indication as to why water quality has not been improved in Uganda‐ because the paying population is unwilling to pay for the entire cost of the project. This deduction is not to suggest that the users do not recognize the benefits of the project. The unpleasant truth is that the users’ incomes are typically stretched so thin by other demands that a decision to make more deductions from these incomes is not an inviting one. However, there is a need to improve water quality in LICs like Uganda, as can be deduced from the analysis of the risks of not doing so and benefits of doing so. Accordingly, such projects have to be funded by mechanism that does not require the users to cover the whole cost, but only part of such a cost, with the remainder from other sources like NGOs and foreign aid.

The purpose of this study was to quantify the effects of land use on water quality in Ladner Slough, and in the major drainages feeding Ladner Slough. Water samples were collected monthly during the winter of 1976 up until the month of April, 1977. Samples were also collected in August 1976 and August 1977. Soil and sediment samples were collected twice throughout the sampling period in order to aid in determining the net effect of various land uses on water quality. Sampling sites were located on Ladner Slough, Cohilukthan Slough, Crescent Slough, and Deas Slough. In that context, they were located within various different land use areas, and within transition zones between land use areas. Concentrations of metals, nutrients, and major cations in water samples were determined. Analogous determinations were made on the soil and sediment samples taken. The results of numerous statistical analyses suggested that iron and total nitrogen were the water quality parameters that are most sensitive to land use in the Ladner area. Some water quality parameter magnitudes in every slough were found to exceed guideline objectives for domestic use in one or more months throughout the study period. Sloughs draining or adjoining urban zones were observed to exhibit generally the highest concentrations of metals. A site near the sanitary landfill area, on the periphery of Burns Bog, also exhibited consistently high metal concentrations. High nutrient concentrations were most often found in conjunction with agricultural land, and probably resulted from point sources. The highest concentrations of major cations were found in the slough which was closest to the Strait of Georgia. Soil and sediment data did not correlate closely with water quality data. Relatively high concentrations of lead were found in the sediment from Ladner Slough. This was thought to result from the heavy marine traffic on that slough, and could represent a potential sink for that metal. The water quality in Ladner Slough did not differ significantly from the water quality of Deas Slough. This implies that the Fraser River may flush both of the above sloughs periodically. The effects of land use on water quality in the Ladner area are discernable, and often pronounced. Moreover, some water quality problems were found to exist. This report recommends that a surface water and groundwater monitoring network be established in the area in order to provide a greater data base, and to better define specific deleterious activities. Emphasis should be placed on nutrients draining from agricultural land, and metals draining from both urban land, and the sanitary landfill area on the periphery of Burns Bog. / Land and Food Systems, Faculty of / Graduate

M.Tech. / South Africa is a water scarce country. The characteristic water pollution problems associated with both developing and developed economies are evident. Indicator organisms have been enumerated from samples collected from the Blesbok Spruit (Gauteng Province) over one year. Standard membrane filtration techniques were used followed by cultivation of E. coli and enterococcus on selective agars. Rainfall data was collected to enable a determination of differences, between “wet” and “dry” sampling runs. Descriptive statistics applied to the data include the calculation of the geometric mean for each sampling run and the geometric mean per sampling site in both wet and dry conditions. The Mann- Whitney Rank Sum Test and Kruskal-Wallis One way Analysis of Variance (ANOVA) were used to compare data sets. The capacity of the Blesbok Spruit, containing wetland areas, to assimilate the microbiological load was more effective than that of the Renoster Spruit (Free State Province) which does not contain distinctive wetland areas. The risk of infection has been determined by comparing the levels of E. coli and enterococcus to a set of site-specific guidelines. The water is not suitable for drinking or domestic purposes and full contact recreation will pose a risk of infection to users. The lower Blesbok Spruit has the poorest water quality and this water is unsuitable for livestock watering being only suitable for the irrigation of crops. The effects of diffuse pollution on the health related microbiological water quality need to be considered in the management of this sub-catchment.

This minor-dissertation established the long-term (July 2002 to June 2006) as well as present day (July 2005 to June 2006) water quality conditions of the Hex River and its tributaries the Dorp-, Paardekraal- , Klipgat- and Klipfontein Spruit, upstream of the Bospoort Dam. The Hex River is situated in the North-West Province, in close proximity of the town Rustenburg. The Hex River falls within the associated Hex River catchment. Various anthropogenic activities impact negatively on the water quality of the Hex River. These impacts include agriculture, livestock production, industrial effluent, mining activities, and processing as well as residential impacts including treated and untreated sewage from the town of Rustenburg as well as informal settlements in the Hex River catchment. The various land uses for the Hex River include domestic use by informal settlements in the area, including mining concessions, livestock watering as well as irrigation and the aquatic environment of the Hex River catchment and the receiving water body the Bospoort Dam. The Hex River, therefore, not only has a effect on the environment but also on the social and economic aspects in the region. Owing to the severity of these impacts it was deemed necessary to determine the long-term water quality trends of the Hex River as well as the prevailing water quality conditions. The primary tributaries of the Hex River were included in the study to determine the source of possible pollution influx. In order to achieve the aim of the study a literature review was conducted on chemical, physical and biological water quality as well as legislative requirements controlling water quality management. A proper understanding of the various impacts as well as land uses in the area is essential in demarcating possible pollution sources. The assessment of the long-term water quality data was conducted to determine the historical water quality trends of the Hex River and associated tributaries and the deterioration in water quality over a four year period. The most recent water quality data were compared against the Target Water Quality Guideline Ranges (DWAF, 1996) for domestic use, irrigation, livestock watering as well as aquatic ecosystems. The long-term water quality trends showed a significant mine water, industrial effluent and sewage impact on the Hex River after the confluence with the tributaries. The assessment of the current water quality situation indicated non-compliance towards the Target Water Quality Guideline Ranges (TWQGR) as stipulated by the Department of Water Affairs and Forestry (DWAF, 1996a-d), rendering the water unfit for domestic use, irrigation and livestock watering. The sources feeding the tributaries iii contain water of inferior quality with a direct associated environmental risk. However, at present the risk potential is contained in the system but with a specific environmental event, such as high rainfall over a short period of time, could be released with a significant environmental impact and decrease in aquatic biodiversity. / Dr. J.M. Meeuwis

Growing populations, urbanization, environmental awareness with resultant regulations and water scarcity have resulted in a search for alternative water sources. Municipal wastewater reclamation and reuse is a necessity in these conditions because it is a water source that is available throughout the year. It can reduce the demand for source water and could be treated at lower costs to the required water quality requirements of the intended use. South Africa especially the Gauteng Province is subjected to the above mentioned stressors but lacks a holistic approach to wastewater reclamation and reuse as a practical and viable solution. Furthermore, the lack of characterization parameters as well as advanced wastewater treatment methods and the viability assessments of the municipal wastewater generated in the South Gauteng catchment, has led to loss of potential water resource in the province. Therefore the current research was initiated as a baseline study to investigate the feasibility of municipal wastewater reclamation and reuse in the South Gauteng catchment. The specific objectives were to 1) assess the worldwide practices of wastewater reuse, 2) apply influent and effluent data analysis and make recommendations on the type of reuse application available for the Southern Gauteng municipal wastewater treatment effluent and to 3) assess the viability of tertiary treatment technologies as best fit options available for different reuse options required for the study area. To achieve the above mentioned objectives a literature review was undertaken to assess worldwide water reuse practices and how they can be used in the study area to utilize the generated wastewater effluent. Influent and effluent data of four wastewater treatment plants (WWTPs) in the Sedibeng district municipality (SDM), three in the Emfuleni local municipality and one in the Midvaal local municipality, was used to assess the viability of water reuse. Available worldwide aggregate, nutrient, ionic and microbiological water reuse standards and criteria for potable, agricultural and industrial use were used to characterize the Sedibeng WWTPs for water reclamation. Wastewater reclamation and reuse is broadly defined as collecting treated or untreated wastewater and using it for a purpose different from what it was used for previously. Recycling, on the other hand, is using water, for the same purpose repeatedly (DWA, 2013a). Water reuse is practiced in countries such as the Western United States, Australia, Singapore, Namibia, Mediterranean countries and Japan for potable use, irrigation and industrial purposes. South Africa, having laid the foundation of wastewater reuse in Namibia, currently practices direct potable reuse (DPR) in the Beaufort West municipality as well as internal water recycling in the power, steel, petrochemical, paper and pulp industry. Water reuse standards and criteria are set based on regional differences of water availability, public health protection, monitoring feasibility, industry types and the reuse purpose. Risk assessment that includes among others a multi-barrier approach, water quality criteria objectives and acceptance determines treatment technology selection. Tertiary treatment technology such as ultrafiltration, reverse osmosis and advanced oxidation processes especially UV/H2O2 are used in water reclamation plants after preliminary treatment of secondary effluent. The four SDM WWTPs effluent, which was over 220 ML/d, the results show, mostly use activated sludge process and have water quality determinants complying with the design criteria for advanced treatment in water reuse. This effluent meets the Namibian Goreangab and Beaufort West Water Reclamation Plant (WRP) multi-barrier influent design criteria for DPR in most aggregate, nutrient and ionic parameters except microbiological parameters. Parameters such as chemical oxygen demand (COD), dissolved solids and ammonia and alkalinity were non-compliant for which this could signify incomplete activated sludge process. This shows the importance of secondary treatment as one of the barriers in the multi barrier approach. Even though membrane treatment of this effluent to improve these parameters and microbiological quality is possible effective secondary treatment as one of the barriers is important to prevent downstream membrane fouling. Depending on this water quality the water will be suitable for indirect potable reuse (IPR) with blending, industrial cooling, heat exchange and dust suppression as recommended uses. Municipal effluent, which could reduce potable water demand, is currently not used in the study area’s power generation and steel making industries Eskom’s Lethabo power station and ArcelorMittal respectively. This is even though, advanced water treatment processes such as reverse osmosis, exist for both organization’s internal wastewater recycling. The reclaimed municipal effluent can be introduced to moderate water quality processes such as cooling systems, heat removal, waste handling and washing in both industries in the study area. Public-private partnerships (PPPs) with water intensive user industries incorporating municipal secondary effluent in current and future infrastructure plans to find viable solutions as part of their water use licensing conditions. These PPPs would include the national Department Water and Sanitation (DWS), Sedibeng district municipality, Eskom, ArcelorMittal and Rand Water the bulk water utility in the study area. An in depth study of water reuse public perception, cost of water reuse, establishing purpose specific reuse guidelines and water quality monitoring and management plan for study area is recommended before implementation. Monitoring, which is one of the barriers in risk abatement, should include for the study area emerging pathogens, inorganic and organic contaminants of concern such as endocrine disrupting chemicals (EDCs). / Dissertation (MSc)--University of Pretoria, 2016. / Centre for Wildlife Management / Unrestricted

A degradação da qualidade de água no Brasil é um problema sério que afeta grande parte dos rios e lagos. O objetivo desse trabalho é discutir quais mecanismos podem ser usados para a melhora da qualidade das águas tendo em vista a garantia dos seus usos. A legislação brasileira prevê que o sistema de gestão de recursos hídricos deve definir os usos pretendidos para as águas das bacias hidrográficas. Nos casos em que a qualidade das águas precisa ser melhorada para garantir os usos pretendidos, o sistema de gestão de recursos hídricos deve estabelecer etapas progressivas, em que, para cada etapa, são definidas metas de qualidade de água específicas. Utilizando como exemplo o sistema de gestão de qualidade de água de diferentes países, essa dissertação analisa o sistema brasileiro, a definição de metas e a sua relação com o sistema de gestão de recursos hídricos, conforme as definições previstas na Resolução CONAMA 357/05, e identifica os desafios e estratégias para superá-los. Também demonstra que, para que haja mudanças efetivas no cenário de qualidade das águas, será necessário para o país um planejamento estratégico, com prioridades definidas de acordo com as especificidades locais, os investimentos necessários e os aspectos econômicos, enfatizando-se o planejamento e o controle dos serviços de saneamento. / Water quality degradation is a serious problem that affects large extensions of rivers and lakes. The purpose of this thesis is to discuss which mechanism can be used to improve water quality in order to guarantee designated uses. The Brazilian water law establishes that the water resource management system must define the designated uses for the watershed. In cases where water quality must be improved to guarantee such uses, the water resource management system establishes a step-by-step system in which, for each step, specific water quality targets are defined. Using as an example the water quality management system of different countries, this thesis analyses the Brazilian system, the target definitions and its relations with the water resource management system, as defined by CONAMA Resolution 357/05, and identifies the challenges and the strategic seams to surpass them. It also demonstrates that, in order to get an effective change in the water quality scenario, it will be necessary for the country to work on strategic planning, with priorities based not only on specific local characteristics, but also on financial needs and economical aspects, with special emphasis on regulation and control of wastewater systems.

A área de estudo se encontra no Município do Guarujá (SP), no litoral do Estado de São Paulo, possuindo uma população de 306.683 habitantes (IBGE, 2014). E por suas praias possuírem grande importância turística, durante períodos de alta temporada essa população aumenta, ultrapassando 900.000 habitantes. Por consequência do aglomerado populacional, milhões de litros de esgotos são gerados diariamente e precisam de uma destinação adequada. A forma escolhida para eliminar boa parte desses esgotos é lançando-os no mar através de emissário submarino, opção estratégica por afastá-lo para longe das praias. Porém, esses esgotos lançados podem interferir negativamente na qualidade das águas costeiras, na flora e na fauna, e nas características físico-químicas das águas da região, além dos riscos à saúde de banhistas caso retornem às praias. Também ocorrem problemas por falta de investimento em infraestrutura, lançamentos de esgotos em rios e córregos da área, interferindo na sua qualidade. A pesquisa consistiu na análise da qualidade ambiental das praias e águas costeiras do Guarujá, através da avaliação da qualidade ambiental da região. Foram consideradas três fontes de poluentes: Emissário Submarino de Esgotos do Guarujá, sete canais artificiais e três rios localizados na praia do Perequê. Dados pretéritos e simulações numéricas hidrodinâmicas e de dispersão foram utilizados na avalição dos níveis de contaminação por esgotos. Os dados pretéritos foram extraídos de relatórios anuais publicados pela CETESB, referentes aos anos de 2008 a 2012, e de estudos realizados pela SABESP (2012). Os resultados do estudo indicaram que as fontes modeladas interferem na qualidade das águas da região. No caso do Emissário Submarino do Guarujá, as interferências com concentrações acima dos limites de balneabilidade ocorrem longe das praias, porém baixas concentrações de esgoto acabam chegando às praias. Já os canais e rios proporcionam grandes riscos à qualidade das praias, lançando suas águas diretamente nessas, inviabilizando seu uso para realização de atividades de contato primário, e expondo os banhistas a riscos de saúde. / The study area is located in the city of Guaruja (SP), on the coast of São Paulo State, having a population of 306,683 inhabitants (IBGE, 2014). And for its beaches having great tourist importance, during periods of high season this population increases, exceeding 900,000 inhabitants. As a result of the agglomeration, millions of liters of sewage are generated daily and need a proper disposal. The form chosen to eliminate many of these drains is cast them into the sea through marine outfall, strategic option for distancing them away from the beaches. However, these cast sewage may negatively impact on the quality of coastal waters, flora and fauna, and the physicochemical characteristics of the water in the region and risks to the health of bathers case return to the beaches. Also there are problems due to lack of investment in infrastructure, sewage spills into rivers and streams of the area, impacting their quality. The research consisted in the analysis of environmental quality of beaches and coastal waters of Guaruja, by evaluating the environmental quality of the area. We considered three sources of pollutants: submarine outfall sewage of Guaruja, seven artificial channels and three rivers located on the beach Perequê. Historical data and hydrodynamic and dispersion numerical simulations were used for evaluation of sewage contamination levels. The historical data were extracted from annual reports published by CETESB, for the years 2008-2012, and studies by SABESP (2012). The results of the study indicated that the sources modeled interfere with the quality of the waters. In the case of Guaruja Submarine Emissary, interference with concentrations above the bathing limits occur away from the beaches, but low sewage concentration end up coming to the beaches. On the other hand, the channels and rivers provide great risks to the quality of beaches, throwing the contaminated water directly in those waters, preventing its use for primary contact activities, and exposing bathers to health risks.

As population increases, the number of water bodies meeting water quality standards tends to decrease. The 1972 Clean Water Act (CWA) addresses the issues of point and nonpoint source pollution by requiring states to compose lists of waters that do not meet water quality standards and develop Total Maximum Daily Loads (TMDL) for those waters. This requirement of the CWA remained inactive until EPA and states suffered lawsuits from environmental groups and concerned citizens. The result prompted a flurry to develop TMDLs in compliance with consent decrees. A variety of methods and models serve as tools to calculate existing loads, load reductions and allocations. The purpose of this study is threefold 1) to examine two methods of TMDL development, Flow Duration (FD) used in Kansas and Hydrologic Simulation Program-Fortran (HSPF) used in Virginia; 2) to compare results of both methods in the same watershed of Virginia; and, 3) to evaluate stakeholder involvement in the TMDL process. A variety of stakeholders such as agencies, towns and industry, agribusiness, and concerned citizen/environmentalists are faced with meeting TMDL reductions and allocations. It is important that the TMDL process and implications are understood by all stakeholders. / Master of Public and International Affairs

Orientador: Maria Célia Portella / Coorientador: Wilson Wasielesky Junior / Banca: Lúcia Helena Sipaúba Tavares / Banca: Rodrigo Schveitzer / Banca: Rosângela Kiyoko Jomori Bonichelli / Banca: Antônio Fernando Monteiro Camargo / Resumo: Com o aumento da demanda mundial de pescado surge uma tendência de intensificação dos sistemas produtivos de criação de organismos aquáticos. Entre os sistemas intensivos de aquicultura, o sistema de bioflocos vem ganhando cada vez mais espaço por ser um sistema relativamente mais simples do que o sistema de recirculação de água e capaz de otimizar a utilização dos recursos hídricos. Apesar do sistema de bioflocos ser atualmente bastante estudado na carcinicultura marinha e na fase engorda de tilápia, a adoção dessa tecnologia na larvicultura de peixes de água doce ainda é um assunto novo e pouco avaliado. O objetivo deste trabalho foi avaliar o efeito de diferentes variáveis de manejo na larvicultura de tilápia-do-nilo neste sistema de criação. Foram realizados quatro experimentos que avaliaram: o tempo de maturação do sistema de bioflocos antes do povoamento das larvas; a utilização de substrato artificial e a adição diária de melaço; a densidade de estocagem das larvas; e diferentes fontes de carbono e relações entre carbono e nitrogênio. Em síntese, o sistema de bioflocos foi eficiente para a produção de juvenis de tilápia em sistemas estático sem a renovação de água, promovendo boa taxa de crescimento e sobrevivência das larvas e melhor aproveitamento da ração (conversão alimentar aparente mais eficiente). A utilização de um inóculo de água contendo bioflocos já estabelecido permite a dispensa de preparo prévio dos tanques de criação anteriormente ao povoamento das larvas, otimizando desta forma as unidades de produção (tanques e viveiros) da piscicultura. A utilização de substratos artificiais não promoveu nenhum beneficio na manutenção dos parâmetros de qualidade de água e no desempenho das larvas criadas no sistema de bioflocos. A adição diária de melaço nos tanques proporcionou melhores... / Abstract: There is a tendency of intensification of aquaculture production systems with the increase in global fish demand. Amongst the intensive aquaculture systems, the biofloc system has been gaining more importance because it is a relatively simple system comparing to the recirculation aquaculture system (RAS), and enables to optimize the use of water resources. The biofloc system is currently widely studied and applied in marine shrimp culture and in tilapia grow out, but the adoption of this technology in larviculture of freshwater fish is still a new subject and scarcely evaluated. The aim of this study was to evaluate different aspects for utilization of this technology during the larviculture of Nile tilapia. Four experiments were performed to evaluate the following issues: time of maturation of the biofloc system before the larvae stocking; use of artificial substrate; daily molasses addition; stocking density; different carbon sources and C/N ratio. In synthesis, the biofloc system was quite efficient for the production of juvenile tilapia in static systems without water exchange, promoting good growth rate and survival of larvae and a better use of the aquafeeds (feed convention ratio more efficient). Using an inoculant containing biofloc water already established dispenses the preparation of tanks prior to larval stocking, optimizing the production units (tanks and ponds) of fish farming. The use of artificial substrates did not promote any benefit in maintenance of the water quality parameters and performance of larvae reared in the biofloc system. The daily molasses addition in tanks improved the larval survival rates. The estimated maximum stocking density that can be used in this low-scale system is up to four larvae per liter. Different organic carbon sources can be used to promote the development of heterotrophic bacteria important for maintenance of this system. Further work should be carried out to assess the use of this ... / Doutor