Innovative, stand-alone, electrochemical treatment integrated eToilet for improved public sanitation – On-field learning for improved results

4 Poster Track: Applied Research » 4 Innovative technology aspects

Speaker: Clement Cid

Summary – for publication in conference brochure:

The eToilet in combination with Caltech’s electrochemical treatment technology presents India’s first water-recycled electronic public toilet. Field trials for two pre-commercialization units (one male and one female) began in April 2019, in Coimbatore, India. These units are completely automated, self-cleaning, and remotely monitored, capable of reusing wastewater. The treated effluent showed 79% reduction in COD, 91% removal of TN, and consistent pathogen removal, with both units together recycling nearly 25,000 L of wastewater. Field learnings paved way for technological improvements which helped achieve consistent closed-loop operation. The one-of-its-kind integrated product is expected to enter the commercial market space in 2021.

Introduction, methods, results and discussion:

The heightened understanding of the imperative need to conserve water resources has been driving efforts into creating a circular economy for water, to build resilient cities for the future. Lack of availability of water for sanitation decreases the sustainable use of toilets. Foreseeing this alarming gap, Eram Scientific Solutions and the California Institute of Technology (Caltech), with the support of the Bill & Melinda Gates Foundation joined forces to develop an innovative integrated sanitation model in which public toilets are clean, safe, automated, self-cleaning, and remotely monitored: the Caltech-Eram Reinvented Toilet (CERT). With the eToilet from Eram Scientific as the front-end and Caltech’s electrochemical reactor (ECR) as the main processing system, the treated water is processed back into the eToilet for flushing and floor washing. 

The first round of field testing of the CERT was carried out between April and October, 2019, at Coimbatore, India. The effluent showed good TN removal (~85%) and acceptable levels of effluent COD. Consistent pathogen removal enabled closed loop operation (reuse of water for flushing). The major hurdle was the marked decline in performance exhibited by the electrodes after 300 hours of run-time. The faulty electrodes were further replaced with mixed Ir-Ru-Ti electrodes (Yixing Entrustech, China). During subsequent field testing with the renewed electrodes, an innovative foam mitigation system was introduced for improved process control of the ECR. The process time for the ECR was reduced from 4 to 3 hours, resulting in an increased capacity of 440 L/day and nearly 25% decrease in energy consumption. With the Ir-Ru-Ti electrodes, the female unit was able to achieve 53 days of continuous operation (24/7), 390 hours of treatment, with 6450 L of water reused. The treated effluent showed 79% and 78% reduction in COD, 95% and 96% reduction in TSS and 90% and 91% removal of TN, in the male and female units respectively, along with consistent pathogen removal.  Taking gender preferences into account, the eToilet exteriors were redesigned using gender-specific colours, the male voice instruction inside the unit replaced, and additional accessories such as sanitary napkin vending machines, and sanitary napkin incinerator added. The units were further optimised to include automated electrode cleaning and pump protection mechanisms, with 8 treatment cycles/day. Remote monitoring of treatment parameters such as oxidation-reduction potential (ORP), colour and turbidity, along with self-diagnosis for malfunction detection enabled smooth and continual operation. 

Further research and re-engineering will focus on the consistent operation of both units in closed-loop mode, and in establishing the lifetime of the newly replaced electrodes. The one-of-its-kind integrated product is expected to enter the commercial market space in 2021. In view of the current COVID-19 pandemic, the incorporation of a UV disinfection mechanism for toilet surfaces is in consideration. 

Conclusions and implications:

The integrated system has carved a niche in public sanitation by bringing together an appealing, clean, hygienic, and safe enclosure with on-site processing of wastewater and its safe reuse or disposal – all, in one, innovative, stand-alone product.  Large-scale commercial production will further lower the cost of production of the system, resulting in an affordable and compact ‘one-stop’ solution, that can cater to the requirements of public toilet usage in India. With the integration of solar cells, the system can run completely off-grid and without city water, or sewer connections. Remote monitoring and management of usage, treatment parameters, and system malfunction, ensures easy maintenance and reduced O&M costs, and help achieve sustained use of the toilet. 

The integrated product hence presents an on-site sanitation system, that is fully automated, off-grid, and closed-loop. The self-sustaining and automated nature ensures a hassle-free user experience. It hence possesses immense potential in improving India’s largely inadequate and unhygienic public toilet infrastructure. 

Relevant references:

None cited.

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