Tratamento De Esgoto

Impacto da desinfecção de efluentes sanitários nos atributos biológicos e químicos do solo Lucas Agnelo* (IC), Noely B. Silva (PG), Fernando P. Candello (Biólogo PAEPE), Jerusa Schneider (PQ). Resumo O ácido peracético e o hipoclorito de cálcio são desinfetantes alternativos que podem ser utilizados no tratamento de efluentes. Desse modo, o objetivo deste trabalho foi avaliar alterações químicas e microbiológicas no solo após a utilização de determinadas concentrações desses desinfetantes, visando o reúso do efluente tratado e desinfetado na agricultura. Para isso foram realizados, primeiramente, ensaios de fitotoxicidade com sementes de alface, a fim de determinar quais doses causam efeitos fitóxicos à germinação. Por meio de tais ensaios, escolheu-se as doses 3 e 25mg/L de ácido peracético e hipoclorito de cálcio, respectivamente, para serem submetidas à respirometria de Bartha e então observar os possíveis efeitos na atividade microbriana do solo. Contudo, ambas as doses não causaram efeitos tóxicos à microbiota e verificou-se que a concentração de hipoclorito de cálcio de 25mg/L possui um maior potencial de biodegradabilidade. Palavras-chave: Desinfecção, Tratamento de esgoto, Reúso.

Owing to low investment and maintenance costs, there has been a growing interest in applying plants in wastewater treatment. Plants commonly used in constructed wetlands (CW) include: cattail, reed, rush, yellow flag, manna grass, and willow.
In a CW, application of plants brings several benefits: creating aerobic conditions in the otherwise anaerobic rhizosphere, providing carbon compounds into the rhizosphere, uptaking pollutants (e.g. nutrients and heavy metals) from treated wastewater; improving the hydraulic conditions of wastewater flow through CW beds, and also increasing the available surface for growth of microbial biofilms. Hydrophytes also have great transpiration potential. Numerous studies have shown the importance of evapotranspiration during hot periods in natural wetlands and also in constructed wetlands. Evapotranspiration affects treatment efficiency in CWs: it increases the concentration of dissolved compounds due to decreasing water volume. Therefore, having regard to the mode of operating (VSSW or HSSW), temperature and influent characteristics (e.g. HLR and wastewater influent loads), the removal efficiency calculated as a comparison between initial and final concentration is lower, than expected from mass balance. Given results from systems in colder (Poland) and warmer (Portugal) climate conditions shows that the difference in methodology of removal efficiency calculation is significant, even if the CWs are operating in different modes. Usually, in the literature removal efficiency is expressed on the basis of concentrations, mostly due to lack of flow rate monitoring. Unfortunately, this may seriously underestimate treatment performance of CWs. This study suggests the need for routine monitoring of flow rate, or evaluation of potential evapotranspiration, to estimate removal efficiency of a CW based on mass balance.

Low pH soils with insufficient organic matter can benefit from the application of reclaimed water (RW) and biosolids. The presence of nutrients also aids plant growth. This paper presents the results of two integrated research studies, both carried out in the Beira Interior Region (Covilhã, Portugal); one used RW for irrigation, the other applied paper mill sludge to agricultural land. In both cases, multiple criteria based on GIS tools were used for site selection. In the first study, the characteristics of RW analyzed over 2 years were found suitable for crop irrigation. The RW had moderate organic content, low electrical conductivity (CE), high nutrient content (N, P), and low concentrations of nitrate, metals and phytotoxic elements (Al, B, Cl and Na). The multi-criteria analysis was carried out taking into account environmental, technical and economic criteria and a suitable area of 30.5 ha was found for RW irrigation. In the second work, the paper mill sludge was considered suitable for application to agricultural land. Its concentrations of N, P and heavy metals did not a present risk for soil contamination and were suitable for soil improvement and crop production. A multi-criteria analysis based on similar criteria was conducted and a suitable area of 253 ha was found for sludge application.