ABSTRACT

In recent years, complex industrial wastewater generated from distillery, heterocyclic, pharmaceutical, chemical manufacturing industries, and so on, has become a major area of concern. These complex efuents are characterized by high chemical oxygen demad (COD), color, presence of recalcitrant intermediates and poor biodegradability, which warrant the need for efcient and sustainable processes for their treatment. Conventional biological treatment processes have severe limitations due to the high recalcitrant nature of these efuents, which often results in ineffective treatment. Alternative physicochemical options are capital and energy intensive and also may generate secondary waste streams. The advanced oxidation processes (AOP) such as wet air oxidation (WAO), ozonation, UV, H2O2, and the like, are emerging techniques and have immense potential for effective treatment of complex efuents. AOPs are characterized by generation of hydroxyl radicals that are highly reactive and can easily degrade/alter/modify recalcitrant/toxic contaminants. They are, however, presently beset with problems of high capital and energy intensiveness and are unsustainable as standalone options. The synergistic combination of AOP pretreatment of complex efuent for biodegradability enhancement followed by biological treatment has potential for providing high treatment efciency along with high overall sustainability. Therefore, the primary emphasis of any advanced oxidative pretreatment process should be on partial oxidation/minimal mineralization leading to the formation of biologically degradable intermediates. Minimum mineralization ensures the process feasibility and economics. This chapter discusses WAO and ozonation as pretreatment options for complex efuent to enhance biodegradability to facilitate subsequent biodegradation via anaerobic and aerobic biological processes. Discussions pertaining to the recent developments in this area along with future challenges and prospects exemplied through relevant case studies are presented.