The effects of the initial C/N ratio on the composting of sewage sludge and cotton residues are not reported in the literature. Understanding the main composting control parameters is essential for a good stabilization of these wastes. Therefore, this study sought to evaluate different initial C/N ratios for the composting of sewage sludge and cotton waste, aiming to find the ranges with the best performance for the process and quality of the final organic compost. In this sense, five mixtures of sewage sludge (S) and cotton residues (C) were prepared and composted with three replications for each treatment in a completely randomized design. Physicochemical parameters were evaluated during composting and in the final organic compounds. A Multivariate Principal Component Analysis (PCA) was applied to evaluate the agronomic quality of organic compounds. The thermal behavior of the mixtures presented differences. The treatments 90C10S, 80C20S and 67C33S showed the highest EXI² index (3566.64, 3448.39 and 2738.89), longer duration of thermophilic phase (12 and 13 days) and better potential for maximum degradation (A) of organic matter (67.5, 61.2 and 65.6%C). The final compounds of 90C10S and 80C20S showed higher pH values (7.9 and 7.5) and higher CEC (123.6 and 114.0 meq/100 g OM). PCA showed similarity in the agronomic quality of organic compounds for 90C10S, 80C20S and 67C33S. The treatment 28C72S (initial C/N ratio of 16.6) presented final pH of 5.3 and did not meet the minimum limit required by Brazilian regulations. Initial C/N relations between 24.9 and 35.2 showed better stabilization of waste and final organic compound with better agronomic quality. GRAPHICAL ABSTRACT

R E S U M O Em função do déficit de abastecimento de água em zonas rurais surge o Programa de Formação e Mobilização para a Convivência com o semiárido: Um Milhão de Cisternas (P1MC), responsável pela implantação de cisternas que proporcionaram o acesso à água potável em dezenas de municípios do semiárido brasileiro. Riachão das Neves - BA é um desses municípios e uma de suas comunidades, Riacho do Pintor, foi beneficiada pelas ações do P1MC. Nesse contexto, o trabalho desenvolvido buscou avaliar a qualidade da água armazenada nas cisternas de Riacho do Pintor e conhecer as técnicas de manejo empregadas pelos seus usuários. Em laboratório, foram mensuradas pH, temperatura, cloro residual livre, cor aparente, turbidez, alcalinidade, condutividade elétrica, coliformes totais e Escherichia coli. Os resultados obtidos foram comparados com o padrão de potabilidade brasileiro, estabelecido pela Portaria 888/2021 do Ministério da Saúde e, em 95% dos casos analisados, constatou-se o descumprimento do padrão. Ademais, em campo, verificaram-se problemas relacionados à limpeza dos reservatórios e ao tratamento da água armazenada para o consumo (principal destinação da água das cisternas), tornando recomendada a implementação de medidas educativas que propiciem a conservação da água de chuva e impulsionem a efetividade de cisternas domiciliares no semiárido brasileiro. Palavras-chave: Abastecimento de água potável; P1MC; Riachão das Neves; Padrão de potabilidade. Evaluation of water quality and management of domestic cisterns in rural community of western Bahia (Brazil) ABSTRACT Public policies aimed at basic sanitation in Brazil were, historically, implemented unevenly. In a scenario characterized by the prioritization of urban areas, there is a service deficit in rural areas that permeates even the supply of drinking water. In this context, the implementation of alternative technologies, which result in advances for the sanitation sector in rural areas, becomes suggestive. Thus, the Training and Mobilization Program for Coexistence with the Semiarid: One Million Cisterns (P1MC) was created, responsible for the implementation of cisterns that provided access to drinking water in dozens of municipalities in the Brazilian semiarid region. Riachão das Neves - BA is one of these municipalities and one of its communities, Riacho do Pintor, benefited from the P1MC actions. In this context, the work developed sought to evaluate the quality of the water stored in the cisterns of Riacho do Pintor and to know the management techniques used by its users. In the laboratory, pH, temperature, free residual chlorine, apparent color, turbidity, alkalinity, electrical conductivity, total coliforms and Escherichia coli were measured. The results obtained were compared with the Brazilian potability standard, established by Ordinance 888/2021 of the Ministry of Health and, in 95% of the cases analyzed, non-compliance with the standard was found. Furthermore, in the field, there were problems related to the cleaning of the reservoirs and the treatment of the water stored for consumption (the main destination of the water from the cisterns), making it recommended to implement educational measures that promote the conservation of rainwater and promote the effectiveness of household cisterns in the Brazilian semiarid region. Keywords: Drinking water supply; P1MC; Riachão das Neves; Potability standard.