A clean production process on oily sludge with a novel collaborative process via integrating multiple approaches

Abstract A clean production process is typically studied for oily sludge that a typical pollutant marked by a variety of pollution indicators, such as high concentrations of organic pollution and heavy metal pollution. However, it remains difficult to quickly and synchronously remove various pollutants from oily sludge up to now. In order to simultaneously reduce organic pollution and remove heavy metal pollutants on oily sludge, a clean production process needs to be developed. Here, chemical and biological processes: subcritical hydrothermal treatments (SHTs) and biodegradation processes (BPs) were organically integrated to develop a novel collaborative process (NCP). The different SHT and matched optimal conditions for the BPs were discussed, and the results showed that hydrolysis of catalyst under high temperature and high pressure (HHC) is the best set of conditions for obtaining new biodegradable substrate (NBS). These conditions can maximize the strength of the follow-up BPs and optimize the degradation effect of oily sludge based on a pure oxygen aeration-activated sludge process (POAAS) and air aeration-activated sludge process (AAAS). The results showed that the newly NCP process not only synergically enhances the advantages of SHT and BP in reducing organic pollution, with the degradation rate of oil content reaching 96.73% and COD reaching 95.79% within 10 days, but also significantly improves removal rate of typical heavy metals content, including Cd2+ up to 79.16%, Cr6+ up to 88.03%, As3+ up to 89.59%, Pb2+ up to 89.2% and Ni+ up to 70.1%. This study provides important research value for the clean production process on oily sludge with multiple pollution indicators.