Onsite Graywater Treatment in a Two-Stage Electro-Peroxone Reactor with a Partial Recycle of Treated Effluent

Abstract

The efficacy of an uncoupled electro-peroxone (E-peroxone) prototype reactor system for the treatment of synthetic graywater is determined. The two-stage E-peroxone process integrates ozonation with the in situ production of hydrogen peroxide (H 2 O 2 ) in a first stage reactor before ozone (O 3 ) is converted via the peroxone reaction to a hydroxyl radical ( • OH). The two-stage prototype reactor system allows for the generation of H 2 O 2 via cathodic oxygen reduction in the first-stage reactor before mixing with O 3 in the second-stage reactor. This approach prevents the degradation of polytetrafluoroethylene (PTFE) coated carbon cathodes by • OH that takes place in a single well-mixed reactor that combines electrochemical peroxide generation with O 3 . The dosage of H 2 O 2 into the second-stage reactor is optimized to enhance graywater treatment. Under these conditions, the uncoupled E-peroxone system is capable of treating synthetic graywater with an initial chemical oxygen demand (COD 0 ) of 358 mg O 2 /L, a total organic carbon (TOC 0 ) of 96.9 mg/L, a biochemical oxygen demand (BOD 0 ) of 162 mg O 2 /L, and a turbidity of 11.2 NTU. The two-stage electro-peroxone system can reduce the initial COD 0 by 89%, the TOC 0 by 91%, BOD 0 by 86%, and the turbidity by 95% after 90 min of treatment. At this performance level, the reactor effluent is acceptable for discharge and for use in nonpotable applications such as toilet-water flushing. A portion of the effluent is recycled back into the first-stage reactor to minimize water consumption. Recycling can be repeated consecutively for four or more cycles, although the time required to achieve the desired H 2 O 2 concentration increased slightly from one cycle to another. The two-stage E-peroxone system is shown to be potentially useful for onsite or decentralized graywater treatment suitable for arid water-sensitive areas.

Production of Sodium Hypochlorite Water Disinfectant from Seawater Desalination Brine

“…The second involves supplying, without limits, the NaOCl needed to sterilize the waters produced by the desalination facilities. The cost effectiveness of OSG for NaOCl has been investigated and confirmed by early reports [8][9][10].…”

The Nexus of Innovation: Electrochemically Synthesizing H2O2 and Its Integration with Downstream Reactions

“…The electro-peroxone method has gained recognition as a novel and efficient form of electrochemical advanced oxidation for water treatment , (Figure b). This process operates by combining in situ generated H 2 O 2 with ozonation.…”

“…These findings underscore the potential of electrochemically produced H 2 O 2 as a robust component in advanced oxidation processes, laying the groundwork for small-scale drinking water purification systems. The electro-peroxone method has gained recognition as a novel and efficient form of electrochemical advanced oxidation for water treatment 82,83 (Figure 7b). This process operates by combining in situ generated H 2 O 2 with ozonation.…”

Technoeconomic Assessment of Electrochemical Hydrogen Peroxide Production with Gas Diffusion Electrodes under Scenarios Relevant to Practical Water Treatment

“…5,15 Due to the fast deterioration of GDE stability in the singlereactor configuration, some researchers have suggested that H 2 O 2 be produced in clean electrolyte solutions in a separate electrochemical reactor and then fed to the main reactor that contains the water to be treated (referred to as the dual-reactor system hereafter). 5,14,15,18 It has been expected that in this way, the lifetime of GDEs can possibly be considerably extended because of the avoidance of exposures to strong oxidants and fouling by complex water constituents. Nevertheless, this hypothesis has yet to be verified.…”