New Research Article by Macintosh et al. 2019

Population growth, tightening effluent discharge requirements and increasing energy costs are driving the wastewater treatment sector to improve energy efficiency and strive towards energy self-sufficiency. Despite many strategies being proposed for improving energy self-sufficiency at wastewater treatment plants (WWTPs), limited case studies have been conducted. This full-scale case study at Grüneck WWTP evaluates the effectiveness of two different strategies and quantifies their plant-wide impact. Grüneck WWTP increased energy self-sufficiency by 24% (from 64 to 88%) through reducing energy consumption with aeration upgrades (8% increase) and increasing energy production with food waste co-digestion (16% increase). The plant-wide analysis indicated that the aeration upgrades did not affect effluent quality; however co-digesting food waste at 20% additional organic load caused some minor downstream impacts including reduced dewaterability, fluctuating biogas quality and solids accumulation. A solar dryer was installed to manage the increased biosolids production resulting from co-digestion. The dryer reduced biosolids transportation costs by 30% with minimal increase in total plant energy (below 2%). Payback periods for the co-digestion facility and blower upgrade were 10 and 17 months, respectively. The solar dryer, however, has a payback period of 30 years. Findings from this case study provide practical knowledge of the trade-offs for different strategies commonly employed to improve energy self-sufficiency at WWTPs. The results provide evidence that there is significant incentive for similar plants to improve energy self-sufficiency through co-digestion and aeration upgrades.

Link