Parasitological risk assessment from wastewater reuse for disposal in soil in developing countries.

The purpose of this work is to analyze the parasitological risks of treated wastewater reuse from a stabilization pond in the city of Piracicaba, in the State of São Paulo (Brazil), and the level of treatment required to protect public health. Samples were taken from raw and treated wastewater in stabilization ponds and submitted to a parasitological, microbiological and physicochemical analysis. The study revealed on treated wastewater the presence of Ascaris sp. and Entamoeba coli with an average density of 1 cysts L(-1) and 6 eggs L(-1), respectively. For Ascaris, the annual risks of infection due to the accidental ingestion of wastewater irrigation were 7.5 × 10(-2) in 208 days and 8.7 × 10(-2) in 240 days. For Total Coliforms and Escherichia coli in treated wastewater, the average density was 1.0 × 10(5) MPN/100 ml and 2.7 × 10(4) MPN/100 ml respectively, representing 99% and 94% removal efficiency, respectively. For BOD, COD, TS and TSS removal efficiency was 69, 80, 50 and 71%, respectively. The removal efficiency for nitrogen; ammonia nitrogen and total phosphate was 24, 19 and 68%, respectively. The average density of helminths eggs in treated wastewater is higher compared to the density of the limit value of ≤1 egg L(-1) and tolerable risk is above the level recommended by the World Health Organization. Multiple barriers are necessary for the reduction of organic matter, chemical contaminants and parasites from treated wastewater. Standards for the sanitary control of treated wastewater to be reused in agricultural irrigation areas should be compiled for developing countries in order to minimize public health risks.

Water treatment plant sludge discharge to wastewater treatment works: effects on the operation of upflow anaerobic sludge blanket reactor and activated sludge systems.

This experiment examined the effects of the discharge of water treatment plant (WTP) sludge into the following three types of wastewater treatment systems: a pilot-scale upflow anaerobic sludge blanket (UASB) reactor, a pilot-scale activated sludge system, and a full-scale activated sludge sequencing batch reactor (SBR). The UASB reactor received 50 mg of suspended solids (SS) of WTP sludge per liter of wastewater in the first phase, and, in the second phase, it received 75 mg SS/L. The pilot-scale activated sludge system received 25 and 50 mg SS/L in the first and second phases, respectively. The full-scale WWTP (SBR) received approximately 74 mg SS/L. The results of the experiments showed that, despite some negative effects on nitrification, there were positive effects on phosphorus removal, and, furthermore, there was the addition of solids in all systems.

Análise parasitológica em efluentes de estações de tratamento de águas residuárias / Parasitological analysis in effluents from wastewater treatment plants

O reúso de esgoto tratado na agricultura tem se consolidado mundialmente como forma de atenuaros efeitos da diminuição da disponibilidade de água de boa qualidade no globo. Contudo, estaprática oferece riscos à saúde pública em razão dos organismos patogênicos capazes de sobreviver no esgoto, entre os quais a OMS destaca os protozoários e os helmintos parasitos do homem. Opresente trabalho teve como objetivos detectar a presença dos parasitos intestinais de importância sanitária presentes no esgoto tratado e verificar os riscos potenciais de acordo com as diretrizes da OMS. Amostras de efluentes foram coletadas em duas estações de tratamento localizadas nacidade de Piracicaba, estado de São Paulo. A média de ovos de helmintos no período de estudo nas ETEs Cecap e Piracicamirim foi de 3,78 e 0,89 ovos L, respectivamente. Sendo assim, os efluentes provenientes da ETE Cecap atendem às condições de reúso indicadas na categoria C. Os efluentesda estação Piracicamirim estão em conformidade com as condições de reúso das categorias A e B, nas quais, segundo a diretriz da OMS (49), são necessários valores menores ou igual a 1 ovo L.