Optimal design of an electrochemical reactor for blackwater treatment

Abstract

Electrolysis of blackwater for disinfection and nutrient removal is a portable and scalable technology that can lessen the need for cities to construct large-scale wastewater treatment infrastructure and enable the safe onsite reuse of blackwater. Several systems for treating wastewater from single toilets are described in the literature, but there are few examples of systems designed to use electrolysis to treat blackwater from nearby toilets, which is a situation more common in densely packed urban living environments. In order to scale a single toilet electrolysis system to one that could service multiple toilets, computational fluid dynamic analysis was used to optimize the electrochemical reactor design, and laboratory and field-testing were used to confirm results. Design efforts included optimization of the reactor shape and mixing to improve treatment efficiency, as well as automated cleaning and salt injection to reduce maintenance and service requirements. © 2020 The Authors. Water Environment Research published by Wiley Periodicals LLC on behalf of Water Environment Federation • Practitioner points • Design of a reverse polarity mechanism to enable in situ electrode cleaning and improve long-term electrode performance. • Optimization of a hopper design and drainpipe location to collect and remove flaking precipitates and mitigate maintenance issues. • Design of an automated salt injection system to guarantee sufficient chloride levels for producing adequate chlorine residuals for consistent disinfection.

Electrochemically mediated precipitation of phosphate minerals for phosphorus removal and recovery: Progress and perspective

“…Other cell designs could also benefit the collection of precipitates. Varigala et al, 2021 adjusted the reactor into a hopper shape coupled with a suction pipe, collecting sediments without interrupting operation, as shown in Fig. 7C.…”

“…(B) Diagram of scalable column-shaped electrochemical reactor with a tubular stainless-steel cathode (Lei et al, 2021b). (C) Design of hopper-shaped electrochemical reactor with a suction pipe (Varigala et al, 2021). Reprinted with permission from Copyright 2019 American Chemical Society, 2021 Elsevier, and 2020 Wiley Periodicals.…”

“…In the lab-scale study, the P precipitates were directly scraped off the cathode after terminating the reactions, which is inapplicable during continuous operation. Attempts have been made to obtain precipitates while minimizing disturbance on the treatment, such as the hopper reactor design and polarity reversal (Takabe et al, 2020;Varigala et al, 2021). However, innovative product collection designs are still desired, such as detachable electrodes, an automatic scrapper, and the sudden increase of current to detach deposits from the cathode.…”

Field testing of an onsite sanitation system on apartment building blackwater using biological treatment and electrochemical disinfection

“…The ECR design was similar to the one described by Cid et al 9 with an improved mechanical design after learning from field testing v1 of the system. 20 Further, two identical CLASS v2 prototypes (unit A and unit B) were retrofitted for the same two sites as v1 (site A and site B, respectively) with independent biological pre-treatment technologies to reduce the nutrient and organic loading in the ECR. A custom-designed sequencing batch reactor (SBR) was deployed at site A, and a commercially available anaerobic-aerobic biodigester (EcoSan, Yixing, China) was deployed at site B.…”

“…The filling and emptying operations, as well as powering of the electrodes for a pre-defined reaction time were handled by the ECR control system. Brine injection (including a software adjustable dosing time) and activation of the stirrer in the ECR 20 were also handled by the ECR control system. The RMCUs timestamped and tracked the operational parameters (the number of ECR and cleaning cycles, fault codes, etc.…”