In this paper, Mechanisms Affecting Water Quality in an Intermittent Piped Water Supply, we use my hard-earned data – collected by hanging out on the side of roads in Hubli and Dharwad, watching over a pressure sensor and a physico-chemical sensor (see Fig. 1 below) and running to collect grab samples for entire days at a time – to understand how water becomes contaminated in an intermittent supply and watch it happen.
Papers don’t convey some of the interesting stories behind the research, so this space is a good opportunity to do so. Like that time that I had these sensors in the bottom of a 3 foot deep hole that had been dug so I could hook them up directly to the pipe. When the water turned on (for which I sat there waiting for a few hours), I noticed water seeping in through sides of the pit – there was a leak somewhere nearby and water started filling, filling, filling – not that slowly – the pit. Not wanting to damage the equipment, I got down in the pit, borrowed a bucket from a sympathetic nearby house, and started bailing the water out. After about 30 minutes of exhausting bailing, a group of school girls crowds around, with one asking, “Auntie, auntie, what are you doing?”. I responded with “I am moving water,” and the girl says “oh” and walks away. I keep bailing. Check out the Supplementary Info (ungated!) Fig. 3 part f. See all that time the pressure was >0 psi? I was there in the pit bailing out water.
Below I’m including some photos of the data collection efforts – and the adventures that come with it.
Kumpel, E. and Nelson, K. L. (2014) Mechanisms affecting water quality in an intermittent piped water supply. Environmental Science & Technology, 48(5), 2766–2775.
ABSTRACT: Drinking water distribution systems throughout the world supply water intermittently, leaving pipes without pressure between supply cycles. Understanding the multiple mechanisms that affect contamination in these intermittent water supplies (IWS) can be used to develop strategies to improve water quality. To study these effects, we tested water quality in an IWS system with infrequent and short water delivery periods in Hubli-Dharwad, India. We continuously measured pressure and physicochemical parameters and periodically collected grab samples to test for total coliform and E. coli throughout supply cycles at 11 sites. When the supply was first turned on, water with elevated turbidity and high concentrations of indicator bacteria was flushed out of pipes. At low pressures (<10 psi), elevated indicator bacteria were frequently detected even when there was a chlorine residual, suggesting persistent contamination had occurred through intrusion or backflow. At pressures between 10 and 17 psi, evidence of periodic contamination suggested that transient intrusion, backflow, release of particulates, or sloughing of biofilms from pipe walls had occurred. Few total coliform and no E. coli were detected when water was delivered with a chlorine residual and at pressures >17 psi.