Develop a green sludge treatment: Effects of a new additive on sludge properties and co-removal of bound water, organics and toxic elements in sludge

In this work, a green, cost-saving and energy-saving chemical was produced to dehydrate and detoxify sludge. Variations of chemical properties, and its effects on co-removal of bound water, organics and risky toxic elements (including Cd, Cr_total, Cu, Pb, Zn, Ni and As) from sludge were investigated. Results showed that potential distribution was a key aspect of sludge reduction and detoxification. Cationic chemical could release almost 86% of bound water from sludge through producing potential difference and re-aggregating sludge flocs. Proteins reduction could largely remove organics with molecular weight between 3.5 × 10³ to 7.5 × 10³ Da, and moreover, humic acids were highly effective on toxic elements removal due to its ion exchange, chelation and complexation on it. Thus, variations of proteins and humic acids can reflect the distribution of organics and elements in sludge. Approximately 73% of organics was removed in flocculation process, and additionally, 54% of risky toxic elements was removed through chelating process and flocs sweeping, weakening its ecological risk by 53.71%. Comparing with the commonly used cationic polyacrylamide, the product can save 38.05–40.64% of electric energy in releasing per-unit bound water, and also can acquire much more environmental benefit at unit cost. This further suggested that chemical addition was a clean and environmentally sustainable way for sludge reduction and detoxification.