Membrane based integrative treatment processes emerge as pot
Membrane based integrative treatment processes emerge as potential solution compared to the conventional techniques. Gisi et al. (2009) presented a treatment scheme for tannery wastewater consisting of a biological pre-treatment and then a polymer as coagulant followed by reverse epinastine hydrochloride with a plane membrane. About 67% of COD was removed by biological pre-treatment and the combined process eliminated the refractory organic compounds. A pilot scale membrane bioreactor was incorporated with powder activated carbon addition and the combined process enhanced the organic removal efficiency (Munz et al., 2007). For recycling of tannery effluent, ultrafiltration was coupled with reverse osmosis process after a conventional physicochemical treatment (Fababuj-Roger et al., 2007). Although there have been technological advances to engineer the membrane pore sizes and surface properties, development of an efficient membrane with anti-fouling property, high chemical and mechanical resistance with high flux and selectivity is still a challenge for the polymeric membrane materials (Singh Lalia et al., 2013). Inorganic membranes, particularly the ceramic membranes can be a sustainable option considering their inertness in the harsh chemical environment and longer life time. In view of this and considering the high pollutant loading of tannery wastewater, ceramic membrane based microfiltration was employed in the current study for a composite tannery effluent collected from a common effluent treatment plant (CETP). The effluent was treated in two ways, i.e. a single stage MF and a two-stage process involving ceramic MF process followed by reverse osmosis with polymeric membrane (Bhattacharya et al., 2013a, Bhattacharya et al., 2013b). While the details of the treatment aspects have been reported in our previous study (Bhattacharya et al., 2013a, Bhattacharya et al., 2013b), the present study focuses on an assessment of the toxic impacts of the treated effluents produced from such processes using snail, Pila globosa as an aquatic model along with a comparison of that of the untreated tannery effluent. The aquatic environment is sensitive to toxic effects of contaminants being discharged with industrial effluent. For monitoring environmental quality and health of aquatic organisms biomarkers are extensively employed (Bolognesi and Cirillo, 2014; Minier et al., 2006, Mdegela et al., 2006). Oxidative stress biomarkers are sensitive, measurable and specific in nature that account of genetic level damage caused due to oxidative stress or other environmental stress causing factors. The various stressors present in aquatic environment exert adverse impact on organisms at cellular level resulting into impaired physiological functions. The xenobiotics in wastewater can cause potential damage in fishes leading to tissue damage in gills, kidney and liver (Ahmad et al., 2004), genotoxicity (Aas et al., 2000), as well as, bioaccumulation in the tissues (Rice et al., 2000). In view of this, an evaluation of the ecological impacts of the treated effluents is essential to analyze the adequacy of such processes for environmental discharge. In a previous study, response of the antioxidative defenses of Euphorbia hirta was observed with respect to a combined treatment approach involving ceramic microfiltration and biosorbent using tannery effluent from different streams, viz. composite effluent, effluent from primary clarifier and secondary clarifier (Bhattacharya et al., 2013a, Bhattacharya et al., 2013b). It was observed that the treatment process resulted in the reduction of toxicity thereby restoring normal activity when compared to control values with respect to changes in various biochemical parameters like protein, amino acid, carbohydrate, DNA, RNA and chlorophyll content, etc. In the current study the efficiency of the membrane based treatment processes for tannery effluent has been analyzed with respect to oxidative stress biomarkers using an aquatic community, i.e. mollusc. Apart from their easy availability, molluscs show well response towards inorganic and organic pollutants and hence used widely for biomonitoring studies. In this study P. globosa was selected as a representing model to understand the effects of untreated and treated tannery effluent. The organisms belong to molluscs group and are edible due to their high protein content. Like other molluscs these organisms are protected by shells, hence it has been significant studying to observe the penetration power of toxicants in the industrial effluent.