Análise da eficiência de um sistema de baixo custo de tratamento de água residuária para fins de reúso agrícola em comunidades rurais e populações tradicionais
Carregando...
Data
2019-07-15
Autores
Silva, Tamires Lima da
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Estadual Paulista (Unesp)
Resumo
Comunidades rurais e populações tradicionais possuem um déficit de atendimento de serviços de saneamento básico, principalmente coleta e tratamento de esgoto. Em pequenos núcleos rurais e assentamentos de povos tradicionais é comum a prática da agricultura, principalmente para a produção de hortaliças. O tratamento da água residuária proveniente de esgoto doméstico para reúso agrícola pode promover melhorias ambientais, sociais e econômicas. Tecnologias de tratamento de água residuária doméstica (ARD) descentralizadas, de fácil instalação, operacionalidade e baixo custo são as opções mais viáveis para instalação em núcleos rurais e assentamentos de povos tradicionais. O objetivo desta pesquisa foi avaliar a eficiência de um sistema de baixo custo de tratamento de água residuária doméstica composto por leito biológico filtrante (LBF) e reator de desinfecção solar (SODIS) para fins de reúso agrícola em comunidades rurais e populações tradicionais. O sistema de tratamento experimental foi instalado na Faculdade de Ciências Agronômicas-FCA, Unesp, Botucatu-SP. Foram utilizados três leitos biológicos filtrantes (LBF’s) instalados em paralelo. Cada LBF apresentava volume útil de 0,16 m3 e consistia de quatro caixas d’água retangulares de fibra de vidro, ligadas em série, preenchidas com meio suporte brita #0 a uma altura de 30 cm. Durante o período de pesquisa a vazão média do efluente secundário proveniente da Estação de Tratamento de Esgoto da cidade de Botucatu-ETE Lageado liberada nos LBF’s foi de 0,15 m3 d-1. O tempo de detenção hidráulica da ARD em cada LBF foi de aproximadamente 1,06 dia. A eficiência dos LBF’s foi avaliada pela análise dos parâmetros: demanda bioquímica de oxigênio (DBO), demanda química de oxigênio (DQO), sólidos suspensos totais (SST), sólidos totais (ST), sólidos dissolvidos totais (SDT), turbidez, pH, nitrogênio total (N), fósforo (P), potássio (K), condutividade elétrica (CE), coliformes totais, Escherichia coli (E. coli) e ovos de helmintos. A ARD tratada nos LBF’S era direcionada para três reatores SODIS (Solar Disinfection) de coloração preta, que apresentavam base de concreto e formato de tronco cônico invertido, nos quais as lâminas de ARD de 10, 15 e 20 cm foram testadas para verificar qual delas seria mais eficiente na inativação de coliformes fecais (E. coli). As três lâminas ficaram expostas à radiação solar por um período de 10 horas (das 08:00 às 18:00 horas) sendo os parâmetros: radiação solar global, temperatura, pH, DQO e E. coli monitorados. Para avaliar a influência das variações da radiação solar ao longo das estações do ano na eficiência do processo de desinfecção, foram realizadas coletas em dois períodos: de maio a julho de 2018 (período outono-inverno), e de dezembro de 2018 a março de 2019 (período primavera-verão). Os LBF’s apresentaram eficiência média de remoção de 50,9%, 86,2%, 95,8%, 41,6%, 97,8% para DBO, DQO, SST, ST e turbidez, respectivamente. A ARD tratada pelos LBF’s e direcionada aos reatores SODIS, após quatro horas de exposição à radiação solar, nos dois períodos testados, apresentou qualidade em acordo com a diretriz estabelecida pela Organização Mundial de Saúde (OMS) para irrigação irrestrita (coliformes fecais ≤ 1.000 NMP 100 mL-1). Na comparação das lâminas de ARD com 10, 15 e 20 cm de profundidade através da análise de variância- ANOVA, com a variável resposta a razão (N/No), em que (No) população de E. coli inicial e (N) população de E. coli remanescente após exposição solar, não foi identificada diferença significativa entre as lâminas testadas. Foram gerados modelos matemáticos que representam a fração da população remanescente de coliformes fecais (N/No) em relação à dose de radiação solar global acumulada nos reatores SODIS. Com os resultados das concentrações de N, P e K na ARD, seu potencial nutricional para produção de hortaliças foi estimado em 536,1 kg ha-1 ano-1 de nitrogênio; 157,68 kg ha-1 ano-1 de fósforo e 504,5 kg ha-1 ano-1 de potássio. A combinação dos métodos de tratamento: LBF e SODIS é uma solução sustentável, de baixo custo e manutenção que pode promover o uso seguro de ARD na irrigação de parcelas agrícolas em comunidades rurais e populações tradicionais.
Rural communities and traditional populations present a lack of basic sanitation services, as collection and treatment of sewage. In small rural areas and settlements of traditional people is common the practice of agriculture, mostly for vegetable production. Domestic wastewater treatment (DWW) for agricultural reuse can promote environmental, social and economic improvements. Decentralized technologies for DWW of easy installation, operationality and low-cost are the most viable options for installation in rural areas and settlements of traditional people. The objective of this research was to evaluate the efficiency of a low-cost system of domestic wastewater treatment consisting of biological filter bed (BFB) and solar disinfection reactor (SODIS) for the purpose of agricultural reuse in rural communities and traditional populations. The pilot study was conducted at College of Agronomic Sciences- FCA, UNESP, Botucatu-SP, Brazil. Three biological filter bed (BFB's) installed in parallel were used. Each BFB presented an effective volume of 0.16 m3 and consisted of four rectangular fiberglass water boxes, connected in series, filled with gravel (size range 4.8 mm-9.5 mm) to a height of 30 cm. During the research period, the secondary effluent from Botucatu City Wastewater Treatment Plant (WWTP-Lageado) used as affluent for the BFB's, presents an average flow of 0.15 m3 d-1. The hydraulic detention time of the DWW in each BFB was approximately 1.06 days. The efficiency of the BFB's was evaluated by the analysis of the following parameters: biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total solids (TS), total dissolved solids (TDS), turbidity, pH, total nitrogen (N), phosphorus (P), potassium (K), electrical conductivity (EC), total coliforms, Escherichia coli (E. coli) and helminth eggs. The DWW treated by the BFB's was directed to three black coloured solar disinfection reactors (SODIS), that presented a concrete base and shape of an inverted truncated cone, where three fixed depths of DWW (10, 15 and 20 cm) were tested in order to verify which of them would be more efficient in inactivating fecal coliforms (E. coli). These three DWW depths were exposed to solar radiation for a period of 10 hours (from 08:00 a.m. to 6:00 p.m.) and the parameters of global solar radiation, temperature, pH, COD and E. coli were monitored. With the goal of evaluating the influence of the solar radiation variations along the year on the efficiency of the disinfection process, DWW samples were collected in two periods: from May to July 2018 (Autumn-winter period), and from December 2018 to March 2019 (Spring-summer period). The BFB's presented average removal efficiency of 50.9%, 86.2%, 95.8%, 41.6%, 97.8% for BOD, COD, TSS, TS and turbidity, respectively. The DWW treated by the BFB's and directed to the SODIS reactors after four hours of exposure to direct sunlight, in the two periods tested, presented quality in accordance with the World Health Organization (WHO) guideline for unrestricted irrigation (Fecal coliforms ≤ 1.000 MPN 100 mL-1). Comparing the fixed DWW depths of 10, 15 and 20 cm by the analysis of variance-ANOVA, with the response variable the ratio (N/No), in which (No) represents the initial population of E. coli and (N) represents the remnant population of E. coli after exposure to solar radiation. The ANOVA results showed that there were no differences statistically significant between the DWW depth tested. Mathematical models representing the remaining fraction of fecal coliforms in the DWW (N/No), in relation to the global solar radiation dose accumulated on the SODIS reactors were developed. The concentrations of N, P and K in the DWW showed that it has a nutritional potential for vegetable production of 536.1 kg ha-1 year-1 of nitrogen; 157.68 kg ha-1 year-1 of phosphorus and 504.5 kg ha-1 year-1 of potassium. The combination of the treatment methods: BFB and SODIS is a sustainable low-cost and maintenance solution that can promote the safe use of domestic wastewater for irrigation of farmlands in rural communities and traditional populations.
Rural communities and traditional populations present a lack of basic sanitation services, as collection and treatment of sewage. In small rural areas and settlements of traditional people is common the practice of agriculture, mostly for vegetable production. Domestic wastewater treatment (DWW) for agricultural reuse can promote environmental, social and economic improvements. Decentralized technologies for DWW of easy installation, operationality and low-cost are the most viable options for installation in rural areas and settlements of traditional people. The objective of this research was to evaluate the efficiency of a low-cost system of domestic wastewater treatment consisting of biological filter bed (BFB) and solar disinfection reactor (SODIS) for the purpose of agricultural reuse in rural communities and traditional populations. The pilot study was conducted at College of Agronomic Sciences- FCA, UNESP, Botucatu-SP, Brazil. Three biological filter bed (BFB's) installed in parallel were used. Each BFB presented an effective volume of 0.16 m3 and consisted of four rectangular fiberglass water boxes, connected in series, filled with gravel (size range 4.8 mm-9.5 mm) to a height of 30 cm. During the research period, the secondary effluent from Botucatu City Wastewater Treatment Plant (WWTP-Lageado) used as affluent for the BFB's, presents an average flow of 0.15 m3 d-1. The hydraulic detention time of the DWW in each BFB was approximately 1.06 days. The efficiency of the BFB's was evaluated by the analysis of the following parameters: biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), total solids (TS), total dissolved solids (TDS), turbidity, pH, total nitrogen (N), phosphorus (P), potassium (K), electrical conductivity (EC), total coliforms, Escherichia coli (E. coli) and helminth eggs. The DWW treated by the BFB's was directed to three black coloured solar disinfection reactors (SODIS), that presented a concrete base and shape of an inverted truncated cone, where three fixed depths of DWW (10, 15 and 20 cm) were tested in order to verify which of them would be more efficient in inactivating fecal coliforms (E. coli). These three DWW depths were exposed to solar radiation for a period of 10 hours (from 08:00 a.m. to 6:00 p.m.) and the parameters of global solar radiation, temperature, pH, COD and E. coli were monitored. With the goal of evaluating the influence of the solar radiation variations along the year on the efficiency of the disinfection process, DWW samples were collected in two periods: from May to July 2018 (Autumn-winter period), and from December 2018 to March 2019 (Spring-summer period). The BFB's presented average removal efficiency of 50.9%, 86.2%, 95.8%, 41.6%, 97.8% for BOD, COD, TSS, TS and turbidity, respectively. The DWW treated by the BFB's and directed to the SODIS reactors after four hours of exposure to direct sunlight, in the two periods tested, presented quality in accordance with the World Health Organization (WHO) guideline for unrestricted irrigation (Fecal coliforms ≤ 1.000 MPN 100 mL-1). Comparing the fixed DWW depths of 10, 15 and 20 cm by the analysis of variance-ANOVA, with the response variable the ratio (N/No), in which (No) represents the initial population of E. coli and (N) represents the remnant population of E. coli after exposure to solar radiation. The ANOVA results showed that there were no differences statistically significant between the DWW depth tested. Mathematical models representing the remaining fraction of fecal coliforms in the DWW (N/No), in relation to the global solar radiation dose accumulated on the SODIS reactors were developed. The concentrations of N, P and K in the DWW showed that it has a nutritional potential for vegetable production of 536.1 kg ha-1 year-1 of nitrogen; 157.68 kg ha-1 year-1 of phosphorus and 504.5 kg ha-1 year-1 of potassium. The combination of the treatment methods: BFB and SODIS is a sustainable low-cost and maintenance solution that can promote the safe use of domestic wastewater for irrigation of farmlands in rural communities and traditional populations.
Descrição
Palavras-chave
Irrigação, Desinfecção solar, Leito biológico filtrante, Reúso de água residuária doméstica, Irrigation, Solar disinfection, Biological filter bed, Reuse of domestic wastewater