بازبینی جامع در مورد تصفیه فاضلاب کارخانه با قدرت بالا در مسیر پیشرفت فیزیکی و شیمیایی و بیولوژیکی Comprehensive review on treatment of high-strength distillery wastewater in advanced physico-chemical and biological degradation pathways

Introduction Agro-processing industries contribute a potential thrive to the economic growth and human development generating a signifcant impact on industrial expansion and poverty reduction by providing various income opportunities, trade and employment. Despite of providing ample scope and prospects to overall agricultural development, the agroprocessing industries generate organic waste that causes potential environmental pollution, if disposed untreated. Organic pollutants provide suitable substrate for bacterial proliferation, which induces threats by lowering the oxygen availability in the water body and due to increased turbidity and colour decreases photo-synthetic growth of stream biota. Wastewater generated by agro-processing industries is the major contributors of organic pollutants and contributes about 65–70% of the total industrial organic wastewater generated in India (Pachauri and Sridharan 1998) (Fig. 1). Among these, maximum pollution occurs from fermentation industries followed by pulp and paper industry as per NEERI ENVIS newsletter, January–March, 2016, Vol. 11, No. 1–3 (http://neerienvis.nic.in/). Most of the countries have stringent regulation and rigorous discharge norms for the disposal of agro-based industrial wastewaters. However, implementation of such norms is quite challenging in few cases, which insists to a steady infusion of cost-efective and innovative technologies with steady research eforts that could be adopted even by small treatment facilities. Fermentation industry generates the major volume of wastewater and contributes to highest pollution load among all agro-processing industries. Since 1980s, the technologies that have been developed and majorly practised by distilleries to treat such large volume of wastewater (12 m3 / kilo litre of alcohol produced) comprise anaerobic digestion (biomethanation), composting and incineration. Around 70% removal and utilization of organic matter occur during biomethanation; however, overall three to four stages of cost-intensive wastewater treatment processes are practised by ethanol-producing industries to reduce down the level of organic load and achieve the efuent discharge limit. Hence, it is necessary to develop treatment processes that can demonstrate higher treatment efciency, requiring lesser energy and footprint. Furthermore, in spite of quite a few eforts on knowledge contribution regarding high-strength ethanol distillery wastewater treatment, the present perspectives on complete bioremediation, wastewater recycling and zero discharge with multiple optimized process steps, to achieve maximum removal of organic pollutants, have never been discussed before. This review reports on recent development and advancement of distillery wastewater treatment, as diferent research groups started exploring possibilities of efective mineralization of highly concentrated organic matter present in distillery wastewater by physical, chemical, biological and integrated processes. Most of the case studies are reported although in laboratory scale, few technologies could demonstrate a proof of concept successfully and are certainly having potentials for feld-scale applications.