Process for potash recovery from biomethanated spent wash with concomitant environmental remediation of effluent

Abstract

Molasses based alcohol distilleries generate highly contaminated, dark coloured and foul smelling effluent (bio-methanated spent wash, BMSW, also known as post methanated effluent). While the prevailing practices for treatment of alcohol distillery effluents operate on the premises of 'liability management', high potassium content of spent wash (ca. 2% w/v in BMSW) offers an opportunity for its utilisation in production of potash fertilizers—a major agricultural input. The present invention provides process for potash recovery from BMSW with concomitant environmental remediation of effluent. The process involves pre-treatment of BMSW followed by potash recovery through selective precipitation technique to produce potash fertilizers and activated carbon while generating a relatively benign effluent (>80% remediation). It may further be possible for the alcohol distilleries to achieve ZLD status by incorporating commercially practiced water recovery techniques (viz., multiple effect evaporation/nano-filtration/reverse osmosis etc.) for downstream processing of the process effluent.