Resolving the relative contributions of cistern and pour flushing to toilet water usage: Measurements from urban test sites in India

Abstract

A challenge in water reuse for toilet flushing in India and other Asian countries derives from pour flushing practices. It is a common assumption that the amount of pour flushed water used for personal cleansing is small in comparison to the cistern flush volume, however there is a knowledge gap regarding the actual contribution of each water source to the blackwater amount. In this study, digital water meters were used to measure the fraction of water from personal wash tap relative to cistern water that is used for toilet flushing. High temporal resolution measurements were carried in three different urban sites in the city of Coimbatore in the southern Indian state of Tamil Nadu where onsite sanitation treatment prototypes that may provide reclaimed water for cistern flushing are being tested. Data collected over periods of up to 2 months show that the contribution of the cistern flush to the total blackwater volume is low (14–40%). These data highlight an important factor to inform interventions designed around water reuse for flushing in world geographies where personal toilet cleansing by water is the common practice.

Open defecation and squat toilets, an overlooked risk of fecal transmission of COVID-19 and other pathogens in developing communities

“…Due to the prevalence of unflushable products in use, open waste bins are often placed in squat toilets to collect used toilet tissues and feminine hygiene products to prevent blockage in drains and downstream sewers. These present an additional source of virus transmission for custodial staff or toilet users themselves, especially in public places such as schools, hospitals, and airports (Sun and Han 2020;Welling et al 2020). When flushed, water from the cistern rushes down rapidly into the bowl, collides with feces, and carries these into the drain through the outlet.…”

“…(a) A toilet cubicle for public access at the author's affiliation in Xi'an, China; (b) residual feces left in the bowl of a squat toilet after flushing. Footsteps were easily contaminated by splashes containing fecal matter and urine during open flushing; (c) users were accustomed to dispose of their used tissues and feminine hygiene products in the open waste bin; (d) a squat toilet in India showing a similar design to those seen in China.Reprinted with a Creative Commons CC-BY license from Elsevier(Welling et al, 2020); (e) a squat toilet used in Africa (Photograph credit: P. Marion/Getty Images, available at: www.trips avvy.com/howto-use-a-squat -toile t-14543 33); (f) a toilet for public access in a traditional coffee shop ("kopitiam") in Malaysia (Photograph credit: www.trave lblog .org/ Photo s/70832 39) Potential transmission modes of COVID-19 in a squat toilet. Human feces and urine drop into the open bowl of the squat toilet.…”

Potential Pitfalls in Wastewater Phosphorus Analysis and How to Avoid Them

“…Raw influent of onsite wastewater treatment technologies is highly variable and impacted by many factors such as number of toilet uses, flush volume, and diet. 34 , 35 We suspect that concentrations of condensed and/or organic P may be significant in influent and in effluent from some technologies with novel solid/liquid separation or solids processing methods.…”

Optimal design of an electrochemical reactor for blackwater treatment

“…RESEARCH ARTICLE fluctuations in EC associated with manual addition of salt to the blackwater in the settling tanks at site B. Closing the loop by connecting treated water to cistern flushing did not eliminate the need for regular salt addition because of the extensive use of fresh water from the personal cleaning tap and continued practice of pour-flushing as studied by Welling and co-workers (Welling et al, 2020).…”

“…Details on the performance testing of the two CLASS versions, overall energy estimates for the improved version, and complete description of the flow through CLASS system have been described elsewhere (Varigala et al., 2020; Welling et al., 2020).…”