Resource recovery from dairy wastewater for circular-economy: a review of opportunities, challenges, and prospects

Abstract Dairy industries generate large volumes of contaminated wastewater, previous research has focused on finding effective treatment technologies to manage dairy effluent. However, in recent years there has been a shift in focus to recovery of material from wastewater to support circular economy. Various products such as biodiesel, fertilizer, biogas, animal feed, bioethanol, electricity can be recovered from dairy wastewater (DWW) using technologies such as membrane technology, chemical precipitation, anaerobic digestion, algae technology and bio-electrochemical system. The feasibility of using these technologies for material recovery have been studied in wastewater. However, these methods are not widely used in large-scale DWW owing to their challenges such as fouling for membrane, High operational cost for anaerobic digestion, bio-electrochemical and chemical precipitation. Hence, this paper reviews the feasibility, challenges and prospects of applying these technologies in the realm of DWW. Biological recovery methods have gained traction for their potential to recover valuable materials in wastewater and are suggested as sustainable options especially for the recovery of materials in DWW with anaerobic digestion being widely adopted in many DWW treatment plants in Poland. Microalgae have also been widely studied and proposed as an alternative method for recovery of materials in DWW since it offers several benefits such as wastewater treatment and subsequent to material recovery. Although microalgae are a promising option, based on the characteristics of DWW, it cannot be used as a sole recovery technology, it needs to be combined with other treatment technologies to attain maximum treatment and recovery of material from DWW. Graphical abstract