Efficacy of gravity-fed chlorination system for community-scale water disinfection in northern Ghana

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.Includes bibliographical references (p. 84-89).Although chlorine is one of the lowest cost ways of providing disinfection, currently billions of people lack drinking water that has had this simple treatment. Arch Chemical's Pulsar 1 unit is an innovation in chlorine dosing in that it is a gravity-fed system which does not require electricity while providing relatively accurate dosing. The purpose of this study is to investigate the technical feasibility of the Pulsar 1 unit using high-test hypochlorite (HTH) as a viable chlorination option for community-scale drinking water disinfection in Northern Region, Ghana. In addition, this study compares the Pulsar 1 unit to the household treatment of the Kosim filter plus Aquatabs. The Kosim filter is a pot-shaped Potters for Peace-type ceramic water available in Northern Ghana, while Aquatabs are an alternate chlorine product comprised of sodium dichloroisocyanurate (NaDCC). A pilot study done in Mali in 2005 by EAU Lambda showed the Pulsar's potential to correctly dose a piped water supply with a flow rate of approximately 42 gpm (9.6 m3/hr). The present pilot study has evaluated the Pulsar system in Ghana and Cambridge, MA at flow rates of 18 gpm (4.1 m3/hr) and 9 gpm (2.0 m3/hr), respectively. This was challenging because the Pulsar was designed for swimming pool applications and thus chlorinated at levels higher than appropriate drinking water. As a result, several modifications were made to lower the chlorine concentrations from the Pulsar system into the appropriate drinking water range. Both the Pulsar 1 and Aquatabs systems were found to be technically feasible. The main two advantages of using the Pulsar system over Aquatabs are the vastly reduced operational costs (in $/m3) of disinfection treatment (about 48 times cheaper) and its ability to reach an entire community (compared to just a single household).(cont.) However, these benefits are gained as a tradeoff for increased system complexity and higher capital costs. Overall there is no "single best option", which means site-specific circumstances should dictate the appropriate technology.by Daniel Cash Fitzpatrick.M.Eng