Submitted to: Soil Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2007
Publication Date: 12/18/2007
Citation: Novak, J.M., Szogi, A.A., Watts, D.W., Busscher, W.J. 2007. Water treatment residuals amended soils release Mn, Na, S and C. Soil Science. 172(12):992-1000.
Interpretive Summary: Water treatment residuals (WTRs) are sediment-containing byproducts leftover from purification of raw water in municipal treatment plants. Municipal treatment facilities add various chemicals that contain elements such as sodium, sulfur, and manganese to purify raw water. Consequently, these added chemicals contribute to the WTRs overall chemical composition. Water treatment residuals are being recycled by applying them to soil to reduce phosphorus movement. Following soils application, it is important to know that WTRs do not release other chemicals that may cause soil fertility concerns. Our research was to determine if WTRs applied to soil would release elements that may cause plant nutrient imbalances. A sandy soil was laboratory incubated with and without WTRs for 60 days. During incubation, the soils were leached with water. The soil and collected water leachate were analyzed for three plant nutrients; sodium, manganese, and sulfur. Our analyses showed that these elements were found in various concentrations in both soil and water leachate of the treated and untreated soil. The sodium and sulfur concentrations were found not to cause a soil fertility concern. However, manganese concentrations were at levels that could cause potential reduction in plant growth. We recommend that a prescreening procedure should be used to determine if WTRs applied to soil will release elements that may cause plant growth problems.
Technical Abstract: Water treatment residuals (WTRs) are drinking water treatment byproducts containing chemicals used to purify raw water. Water treatment residuals are used to remediate P-enriched soils. Following soil application, elements present in WTRs have the potential of converting to soluble forms and cause chemical imbalances in soil and ground water systems. This study's objectives were to: 1) examine Mn, Na, S and total organic carbon (TOC) released from soil and deionized water leachate from a Norfolk soil (fine-loamy, kaolinitic, thermic Typic Kandiudult) incubated for 60 d with 0 (untreated) and 60 g/kg of three different WTRs; and 2) assess effects of oxidation-reduction potential (ORP) on Mn stability and solubility. During incubation, treatments were maintained between 5 and 10% moisture and ORP was measured using a Pt electrode. Following 60 d, treatments were leached with 1.2-pore volumes of deionized water. Soils were then analyzed for Mn, Na, and S, and leachates were analyzed for TOC and similar elements using inductively coupled plasma (ICP) spectroscopy. At this time, WTR-treated soils were slightly acidic, moderately reduced, and enriched in extractable Mn, Na, and S concentrations. Water leachates from WTRs treated soil were also enriched with Mn, Na, S, and TOC. Divalent Mn was the dominant oxidation state making Mn more susceptible to leaching. One WTR caused the Norfolk soil to have Mn concentrations that exceeded crop sensitive stress threshold levels. It is recommended that a prescreening procedure should be used to determine if WTRs applied to soil will release elements that may cause plant growth problems.