A Novel Mechanism to Decrease Water Consumption in Commodes

Abstract

Human waste management is a water intensive yet, essential activity. In an average household, flushing is the largest water intensive task, accounting for over 30% of the overall water consumption. A reduction in water consumed in commodes will not only enable the conserved water to be utilized for other vital activities such as agriculture, but also be of monetary benefit in terms of electricity conservation. The S-trap of the commode is identified as the component that entails high water consumption. The S-trap works by creating a depth seal, which is impermeable to the toxic gasses from the sewer. In this experimental study, a novel mechanism is developed to functionally replace the water intensive S-trap of a commode. The hyperboloid valve, essentially, a silicone membrane that alternates between a smooth conduit and an air-tight constriction, is triggered by a simple twisting action. An impermeable seal is formed when the membrane is twisted close, and a free passage when it is twisted open. The overall mechanism comprises a flexible silicone tube, threaded adapters, a gear-based actuation system and a programmable motor. A 1: 1 model of the system was fabricated. The quantity of water used, time of valve open, time between valve open and flush actuation, slope, and water retained in the bowl were the vital input parameters recorded as part of the study. To precisely adjust these parameters, a microcontroller was used to trigger the flushing action. Experimentation with solid waste mock ups such as vegetable dices revealed that the smooth conduit permits free passage of waste unlike the S-trap design. In order to minimize the number of trials during experimentation without compromising on the quality of data collected, a Taguchi L16 array was employed. A quadratic regression equation revealed that for an effective flush, a threshold quantity of water of approximately 1.2 litres is required. Additionally, the weight of waste flushed out was maximum when the valve opening and flush actuation were in synchrony. Three dimensional surface and contour plots were generated to visualize and draw inferences about the effect of the input parameters on the amount of waste flushed. This novel design can be implemented in squat and sitting commodes alike. With a simple yet robust design, the hyperboloid mechanism vies to make flushing a more sustainable process. A large-scale adoption of the same is envisaged to lead to global water and energy savings.