Dairy Wastewater Treatment through Synergies of the Biological and Hybrid Membrane: A Systematic Review

Wastewater treatment techniques have two categories: pre- and post-treatment. Physical, chemical, and biological pretreatment techniques are commonly employed to treat dairy wastewater. Secondly, dairy wastewater post-treatment techniques include physico-chemical and membrane treatment approaches. This review article aims to critically examine and describe pre- and post-treatment techniques for dairy wastewater treatment. The benefits, drawbacks, performance comparisons, and features of each pre - and posttreatment have been extensively investigated. This article uses a systematic literature review method to review and examine other research findings. The results indicate that despite extensive studies on pre- and post-treatment techniques, both have limitations. In this context, aerobic pre-treatment, for example, has high lactose levels, low water capacity, and efficiency concerns. Furthermore, anaerobic pretreatment has issues with lengthy starting times, a high fermentable lactose content, poor residual alkalinity, and fat consumption. In physico-chemical post-treatment, there are high amounts of sludge production and high quantities of chemicals required for pH corrections. Likewise, membrane post-treatment, for instance, has a short membrane lifespan, low selectivity and flux, linear up-scaling, and concentration polarization membrane fouling. Therefore, a synergy of physico-chemical and aerobic, for example, adsorption-aerobic, and synergy of pre-hydrolysis and anaerobic, such as enzymatic hydrolysis-anaerobic treatment, will help to overcome the drawbacks of both anaerobic and aerobic treatment techniques. In conclusion, the most promising techniques for dairy wastewater treatment are combinations of adsorption-aerobic and enzymatic hydrolysis-anaerobic with microfiltration, nanofiltration, reverse osmosis, and ultrafiltration.