REMOVAL OF PHOSPHORUS BY DRINKING WATER TREATMENT RESIDUALS COLLECTED FROM VARIOUS GEOGRAPHIC LOCATIONS IN THE UNITED STATES

The use of fertilizers to promote plant growth is widespread in both agriculture as well as in lawns and gardens in both rural and urban areas. Despite their high efficiency in boosting plant growth, excessive fertilizer use has resulted in the contamination of surface water bodies through runoff, which results in negative environmental impacts, such as eutrophication. To alleviate surface water eutrophication caused by excessive phosphorous, the limiting nutrient for eutrophication in inland waters, removal of phosphorus during wastewater and stormwater treatment processes is essential. Water treatment residuals (WTRs), which are byproducts of drinking water treatment processes have been long recognized as good adsorbent materials for phosphorus, especially aluminum-based WTRs (Al-WTRs). The easy availability of Al-WTRs at no cost from drinking water treatment plants all over the United States makes them a particularly good candidate for phosphorus treatment. However, there is a need to understand how the performance of Al-WTR is influenced by their physicochemical properties before considering large-scale application. A measurable factor to predict WTRs’ phosphorus adsorption capacity would be of great interest to stakeholders. Therefore, this study explored the most representative variables that can be used as efficiency indicators. Thirteen Al-WTRs from different water treatment plants in the United States were examined in terms of their physicochemical characteristics and their effectiveness viz. phosphorus adsorption. The relationship between the characteristics and adsorption capacities was determined using multilinear regression. Results showed that for all Al-WTRs, phosphorus adsorption capacity was in the range of 1.20 – 28.72 mg/g. Among the various physico-chemical parameters, oxalate extractable aluminum, oxalate extractable iron, and sulfur contents in Al-WTRs offered optimal correlation with phosphorus adsorption capacity (R² > 0.87, p < 0.05), with oxalate extractable aluminum content contributing most to the correlation. Our results show that Al-WTRs are indeed promising adsorbents for phosphorus removal, and their removal efficiencies could be estimated by measuring the above three physico-chemical properties prior to large-scale application.