1st International Conference on Rain Water Cistern Systems
Honolulu, Hawaii, USA - June 1982

Section 4: Water Quality

Page 233

Quality of the St. Thomas, US. Virgin Islands Household Cistern Water Supplies

G. Fred Lee & R. Anne Jones
Colorado State University, USA

Abstract

A study was conducted in December 1972 to determine the characteristics of individual household cistern water supplies locate on St. Thomas in the U.S. Virgin Islands. Twelve cistern supplies as well as several other water sources, including the domestic water supply for Charlotte Amalie, St. Thomas and several well water supplies, were sampled. Measurements were made of specific conductance, alkalinity, pH, Ca, Mg, Na, K, Cl S04, total P, N02, N03 NH4, organic N, F, Zn, Ca, Cd, Pb, Cr, Ni, Fe, Mn an Hg. It was found that all of these contaminants' concentrations were below U.S. EPA water quality criteria except for Hg, whose concentrations exceeded the U.S. EPA regulations.

Individual household cistern water supplies did of appear to be contaminated to a significant extent by materials of construction or painting of the rooftop collection system. While the chemical characteristics of the cistern water supplies were in general satisfactory in terms of drinking water quality, other studies have shown that these systems tend to be contaminated with faecal coliforms and that large amounts of decomposing organic materials, such as leaf litter, tend to accumulate in the storage tank. A recommended maintenance program is presented, which includes disinfection with chlorine, periodic removal of accumulated debris from the bottom of he tank, and periodic sampling for measurement of sanitary and chemical quality.

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