A novel concept to integrate energy recovery into potable water reuse treatment schemes

Abstract

Potable water reuse applications can provide a safe and sustainable water supply where conventional freshwater resources are limited. The objectives of this study were fourfold: (i) to analyse existing potable water reuse applications regarding operational characteristics and energy demands, (ii) to determine the theoretical energy potential of wastewater and identify opportunities for energy recovery, (iii) to define design requirements for potable water reuse schemes that integrate energy recovery and (iv) to propose strategies for more energy efficient potable water reuse schemes. Existing potable water reuse schemes commonly utilize conventional wastewater treatment processes including biological nutrient removal followed by advanced water treatment processes. While meeting high product water quality, these treatment schemes are characterized by relatively high specific energy demands (1.18 kWh/m3). Given that the theoretical energy potential of municipal wastewater is approximately two times higher (2.52 kWh/m3), opportunities exist to integrate energy recovery strategies. We propose three alternative potable water reuse schemes that integrate energy recovery from carbon via methane and nitrogen via either the coupled aerobic–anoxic nitrous decomposition operation process or partial nitritation/anammox. Compared to conventional potable water reuse schemes, the energy requirements of these schemes can be reduced by 7–29% and the overall energy balance by 38–80%.

Achieving energy neutrality in wastewater treatment plants through energy savings and enhancing renewable energy production

“…The direct energy recovery from waste nitrogen has recently proven feasible using the coupled aerobicanoxic nitrous decomposition (CANDO) process (Scherson et al 2013). The chemical energy of nitrogen compounds can be estimated to approximately 0.3 kWh/m 3 of wastewater (Horstmeyer et al 2017). This energy can be recovered from nitrogenous oxygen demand (NOD) bound in reactive forms of nitrogen if the nitrogen can be removed from wastewater and processed to generate heat or electricity.…”

Recovery of Nitrous Oxide from Wastewater Treatment: Current Status and Perspectives

“…The CANDO process managed to recover N 2 O through partial denitrification by heterotrophic bacteria . This process involves three stages (Figure ): (I) nitritation, NH 4 + → NO 2 – under aerobic conditions by AOB; (II) nitrous denitritation, NO 2 – → N 2 O under anoxic conditions by heterotrophic denitrifying bacteria; and (III) conversion of N 2 O to N 2 with energy recovery via co-combustion with CH 4 derived from anaerobic digestion. , Compared with conventional nitrification and denitrification processes, the CANDO process has the following theoretical advantages: (1) 60% less chemical oxygen demand (COD) for nitrogen removal, (2) 60% less biomass production, (3) 25% less oxygen demand for aeration, and (4) enabling energy recovery by saved COD and N 2 O recovery (−5.93 kWh/kg of N, compared with 2.38 kWh/kg of N for conventional nitrification and denitrification). , Published research on CANDO is summarized in Table . Since the concept of N 2 O recovery using the CANDO process was proposed in 2013, a number of studies have evaluated and demonstrated the CANDO process in long-term laboratory operations (Table ).…”

Energy audit in water supply systems: a proposal of integrated approach towards energy efficiency

“…Water supply system is a very complex and energy-intensive infrastructure which represents 7% of consumption of world global energy (Coelho & Andrade-Campos, 2014). Horstmeyer et al (2017) compiled the range of energy demands for water treatment (no water conveyance and distribution included) from different authors that shows that WSS can be more energy-intensive depending on the type of water source (see Table 1).…”