Integrated recovery of nutrients during municipal wastewater treatment and biosolids management

There is an increasing push for wastewater treatment (WWT) plants to convert into resource recovery facilities, with an overall aim for the integrated recovery of nitrogen (N), phosphorus (P), and carbon (C). This literature review evaluates the effectiveness of various municipal WWT systems and biosolid management processes for the integrated recovery of these nutrients. Results indicated that when recovering P, N and C, no single WWT system configuration is superior to others in all settings. Instead, a careful combination of processes needs to be matched to the specific wastewater and biosolids characteristics of a WWT facility. Generally, P is primarily retained in biosolids, while C and N retention varies depending on the system design. An integration of enhanced biological phosphorus removal with N-assimilating heterotrophs is proposed for energy-efficient recovery of the three nutrients from wastewater with high chemical oxygen demand (>550 mg/L) with potential average recovery rates of 90%, 79% and 67% for P, N and C, respectively. In low chemical oxygen demand (<350 mg/L) systems, the sequential or combined application of chemical precipitation and phototrophic N-assimilation offers a viable approach to enhance integrated nutrient recovery. Phosphorus recovery has been reported as economically feasible in both mainstream and sidestream processes but recovering N from the mainstream is still generally challenging, with the focus being on N recovery from sidestreams. However, using N-assimilating organisms provides an opportunity for increased energy-efficient N recovery from the mainstream, thereby reducing N losses to the atmosphere. • Strategic process configurations can recover N, P and C instead of one nutrient. • Mainstream N can effectively be recovered using N-assimilating organisms. • Proposed system designs for integrated recovery of N, P and C are COD dependent. • N-assimilating heterotrophs are more efficient for N recovery in high COD water. • N-assimilating phototrophs are more suited for low-COD wastewater treatment.