A method for determining the treatment dosage of drinking water treatment residuals for effective phosphorus immobilization in sediments

Drinking water treatment residuals (WTRs), non-hazardous by-products generated during treatment of drinking water, can be reused to immobilize phosphorus (P) in sediments for eutrophication control. Prior to application, it is necessary to determine the treatment dosage of WTR to immobilize P in sediments. In the present study, the dosage of Al/Fe based WTRs required to effectively immobilize P in lake sediments was determined in a laboratory setting as a function of the oxalate-extractable Al (Alox) and Fe (Feox) content of the WTRs by completely mixing Al/Fe based WTRs with Lake Baiyangdian sediments. The results showed that the capacity for immobilization of mobile P (Pm) in sediments by Alox and Feox in Al/Fe based WTRs ((Alox + Feox)WTR) can be described by the equation: (Alox + Feox)WTR = 83*Pm-40 (where Alox, Feox and Pm are expressed in μmol g−1). This equation was successfully used to determine the respective quantities of three different Al/Fe based WTRs required to immobilize P in sediments from Lake Chaohu, Lake Taihu, the Changjiang River, the Haihe River, the Pear River and the Yellow River. Using the equation derived herein, the required Al/Fe based WTR application dose can easily be determined where the Pm content of the sediment and the Alox and Feox content of the WTR are known.