The Effects of Water Quality Characteristics on Pollutant Releases from Drainage Materials
The purpose of this study was to investigate heavy metal releases from different pipe, gutter, and storage tank materials under a wide range of environmental conditions. The influence of pH, salinity, and time of contact were examined. The awareness of the quantity of the pollutants released by the piping materials will facilitate the design of stormwater control equipment to decrease the toxic effect on the organisms in receiving waters. The data on pipe and gutter stormwater quality runoff will aid officials in making better regulatory policies for industrial and commercial land uses and will be useful in stormwater modeling.
Two series of long term-leaching laboratory tests were conducted using eight new gutter and pipe materials. First series of experiments were conducted to investigate the heavy metal releases under controlled pH conditions. The materials were immersed into locally collected roof runoff and parking lot runoff that were adjusted to pH 5 and pH 8 values using buffer chemicals added to the runoff water (disodium phosphate dehydrate and potassium phosphate monobasic). These buffered runoff waters had high phosphate and high conductivity values. During the second testing stage, materials were immersed into un-buffered waters from Mobile Bay (saline) and the Black Warrior River. These experiments were performed to investigate the metal releases under natural pH conditions with varying salinity values associated with natural brackish bay water and river water.
The analyses showed that pipe and gutter materials can release substantial metal concentrations and can be a significant source of toxicity. The highest lead and zinc concentrations were observed for galvanized steel samples under buffered and natural conditions during both short and long exposure. After 1 day of exposure, zinc releases were exceeding 14 mg/L under pH 5 conditions and 8 mg/L in bay water samples. The greatest copper release was, unsurprisingly, observed from copper materials. Model fitting was performed on the time series plots.
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