Fertigation with domestic wastewater: Uses and implications

The use of wastewater in agriculture is an alternative means of reducing wastewater release into water sources. This process, known as fertigation is an opportunity to make use of organic matter and other nutrients in wastewater for agricultural productivity. The presence of organic matter in these effluents serves as biofertilizer. Since 19th century in Britain, fertigation had been widely accepted due to the scarcity of water, the large amount of sewage produced and the concern about the final destination of wastewater. However, salinization, contamination of soil and agricultural products with the microbial pathogens and presence of heavy metals may limit the use of wastewaters in agricultural system. Thus, the plantation of agronomic varieties that do not have direct use as human food are optional cultivars, which may not have implications of fertigation with domestic wastewater. Fertigation with wastewater will be a nutritive support for the cultivation of Brachiaria brizantha cv Marandu in cerrado soil that is considered as low fertility soil. Soil microorganisms are fertility indicators. For example, nitrogen fixing bacteria (NFB) and arbuscular mycorrhizal fungi (AMF) has great potential to assist in the development of plant varieties under irrigation with domestic wastewater. These microorganisms are good parameters to be used in the analysis of changes that occur when sewage is applied into the soil. Furthermore, microbes contribute to the structuring of the soil, degradation of organic matter and nutrient availability to the biotic component of soil. Despite the limitations of fertigation with domestic sewage, it is a great alternative to use wastewater for nutritional enrichment to the soil that will be used for planting of agricultural crops of commercial interest.Key words: Brachiaria brizantha, agriculture, salinization, diazotrophic bacteria, mycorrhizal fungi

Mombaça grass fertirrigation with different application rates of primary sanitary wastewater effluent treatament, established on the basis of the applied sodium dose

Os esgotos sanitários constituem-se na principal fonte poluidora de grande parte dos rios brasileiros. A utilização dessas águas residuárias na agricultura é uma alternativa para se minimizarem os problemas ambientais causados pelo lançamento desses efluentes em corpos hídricos, além da disponibilização de água e fertilizantes para as culturas, e é também ótima alternativa de incremento na produtividade agrícola. Sendo a agricultura a atividade que utiliza a maior quantidade de água, mas podendo tolerar águas de qualidade inferior, torna-se crescente a tendência de nela se encontrar a solução para os problemas relacionados à destinação de diversos tipos de efluentes líquidos. Entretanto, a utilização de águas residuárias na agricultura exige a adoção de técnicas que minimizem os riscos de contaminação do agricultor, do solo e das plantas. Este trabalho teve como objetivo geral avaliar as possíveis alterações: físicas e químicas do solo, nutricional da planta e possível contaminação das plantas com micro-organismos presentes no efluente de tratamento primário de esgoto sanitário. Para que esses objetivos fossem alcançados, montou-se um experimento em delineamento inteiramente casualizado, que consistiu de cinco tratamentos com quatro repetições. Os tratamentos impostos, referentes à aplicação do efluente do tratamento primário de esgoto sanitário (ETPES), foram: T0: tratamento com aplicação de água de poço artesiano, 0 kg ha-1 de Na+, T1: aplicação de uma dosagem de 75 kg ha-1 de Na+, T2: 150 kg ha-1 de Na+, T3: 225 kg ha-1 de Na+, T4: 300 kg ha-1 de Na+. Amostras de solo foram coletadas nas profundidades de 0-10, 10-20, 20-30 e 90-100 cm para análises físicas e químicas. Amostras do capim mombaça foram coletadas para análises químico-bromatológicas e microbiológicas (coliformes totais e termotolerantes). A análise estatística consistiu na análise de variância e teste de médias, para efeito de comparação das variáveis dependentes, nos diferentes tratamentos aplicados. Os resultados obtidos permitiram concluir que a aplicação do ETPES do CEULPULBRA, proporcionou aumento na produtividade de matéria verde e matéria seca do capim-mombaça, sem alteração na sua composição químicobromatológica, e não detectou a contaminação das plantas com coliformes totais e termotolerantes. No que se refere ao solo, o ETPES, não proporcionou dispersão de argila nas diferentes profundidades do solo, entretanto ocorreu aumento, ao longo do tempo de sua aplicação, nos teores de Na+ trocável, além de expressiva lixiviação de nitrato no perfil do solo. A aplicação do ETPES em altas taxas proporciona potenciais riscos de salinização do solo e de contaminação de águas subterrâneas.The municipal wastewater is considered the main pollutant source of the great part of the Brazilian rivers. The use of such wastewater in agriculture is an alternative to minimize the environmental problems caused by these effluent disposals in water bodies. Besides water availability and fertilizes for the cultures, it is also an excellent alternative in the agricultural productivity increment. Taking into consideration that agriculture is a practice that uses the highest amount of water and that it can also use low quality water, it has become a growing tendency to find in it the solution for the wastewater related problems destination. However, the wastewater use in agriculture demands techniques that minimize the farmer, soil and plants contamination risks. The aim of this work was to evaluate the probable physical and chemical soil alternations, nutritional plant alternations and also some probable plant contamination with microorganisms that are present in the primary domestic wastewater effluent. In order to achieve these goals, an experiment in randomized designed was performed. It was constituted of five treatments with four repetitions. Referring to the primary domestic wastewater effluent (PSWET) application, the treatments were: To: water of the well, 0 kg ha-1 of Na+, T1: application of 75 kg ha-1 of Na+, T2: application of 150 kg ha-1 of Na+, T3: 225 kg ha-1 of Na+, T4: 300 kg ha-1 of Na+. Soil samples were collected in the depths of 0-10, 10-20, 20-30 and 90-100 cm for physical and chemical analyses. Mombaça grass samples were also collected for the chemical- bromatological and microbiological (total and fecal coliforms). The statistical analysis consisted in the variance analysis and average tests for the comparison of the dependent variable effect in the different applied treatments. The obtained results permit to conclude that the PSWET from CEULP-ULBRA provided raise in the green matter productivity in the dry mombaça grass matter without alteration in the chemical-bromatological composition. Furthermore, contamination of plants with total and fecal coliforms was not detected. Regarding the soil, the PSWET did not provide clay dispersion in different soils depths. On the other hand, there was an increase in the Na+ exchangeable concentration and a significant leaching nitrate in the soil profile as the time went by. The application of PSWET in high rates leads to potential salinity soil risks and subterranean water contamination