Energy and resource recovery from a future aerobic granular sludge wastewater treatment plant and benefit analysis

The sustainable approach to energy and resource recovery from excess sludge is gaining traction. This study compared the benefits of methane production through anaerobic digestion (AD) and the recovery of alginate-like exopolymers (ALE)/phosphorus (P) from two types of aerobic granular sludge (AGS). Bacterial and algal-bacterial AGS produced similar methane amounts, around 292 and 287 mL/g-VS_added, respectively, over 30 days, with 72% and 80% biodegradability. After ALE extraction, the remaining AGS showed a 48–56% decrease in methane production without pH adjustment. However, a conceptual wastewater treatment plant (WWTP) processing 10,000 m³/d of wastewater with ALE/P and methane recovery yielded the highest net profits, approximately 66.3 thousand USD annually, when algal-bacterial AGS was used, compared to 59.2 thousand USD for the bacterial AGS-based WWTP. These findings provide valuable insights for developing a sustainable wastewater industry and future WWTP design. © 2024 Elsevier B.V.