This work investigated the potential for reusing water treatment residuals (WTRs) to immobilize phosphorus (P) in the sediments of Lake Taihu and Lake Baiyangdian. The results indicated that WTRs made inorganic P more stable in the sediments, although the sediments from each lake had dissimilar properties. Conversely, WTRs had no effect on the activity of organic P. However, after the sediment was mixed with WTRs, the inorganic P was immobilized in 10 days. Microbiological analyses further revealed that WTRs could alter the structures of the microbial community within the sediments but exert no adverse effect on the bacterial diversity. Moreover, WTRs were found to be beneficial to microorganism growth. Because of the effects exerted by WTRs, the total abundance of bacteria in the sediments increased from 5.10 x 10(12) to (0.66-4.81) x 10(14) copies g(-1) for Lake Baiyangdian sediments and from 1.16 x 10(13) to (1.08-7.14) x 10(14) for Lake Taihu sediments. Therefore, Wilts can be safely used to immobilize P in sediments for the purpose of lake restoration. (C) 2012 Elsevier B.V. All rights reserved.