Treatment of soaking effluent from a tannery using membrane separation processes

A hybrid separation process involving gravity settling, coagulation by alum followed by nanofiltration and reverse osmosis is attempted for treatment of soaking effluent of a tannery. The optimum alum dose is identified. The fertilizer value of the dried sludge is also evaluated. The membrane separation experiments are conducted in a continuous cross flow mode. The hydrodynamics in the membrane cell is altered by conducting experiments under laminar, laminar with turbulent promoters and turbulent flow regimes. The effects of different operating parameters on permeate flux improvement are experimentally observed. A simple resistance-in-series model is proposed to quantify the flux decline during membrane separation processes. The steady state polarized layer resistance is related to the operating conditions, namely, transmembrane pressure and Reynolds number. The transient flux decline is quantified by a first order kinetic model and the kinetic constant is evaluated. The performance criteria are evaluated in terms of COD, BOD, TDS, TS, pH ,Ca2+ concentration, Cl− concentration and conductivity of the permeate.