Municipal sludge samples (SS) were collected from 46 cities in China in 2016. The forms in which phosphorus occurred in the SS were evaluated using the Standards, Measurements and Testing (SMT) Program. The results showed that the average contents of total phosphorus (TP), inorganic phosphorus (IP), non-apatite inorganic phosphorus (NAIP), apatite phosphorus (AP), organic phosphorus (OP), and bioavailable phosphorus (NAIP+OP) in the SS were (17.32±5.13), (11.71±4.01), (9.18±3.44), (3.03±2.74), (4.54±4.23), and (13.72±4.36) g·kg-1, respectively. IP was the main form of phosphorus in the SS, accounting for more than 60% of the TP content. NAIP was the main form of IP, accounting for more than 66% of the IP content. There was a highly significant positive correlation between TP and bioavailable phosphorus in the SS (r=0.942, P<0.01), and bioavailable phosphorus accounted for 66.8%-96.1% of the TP content. The contents of phosphorus in the SS and the amounts of phosphorus discharged via SS disposal showed a decreasing trend from the east to the west of China. In 2016, the amount of phosphorus discharged into the environment via SS disposal amounted to 1.04×105 tons, of which 1.95×104 t entered the soil through SS land application, 4.69×104 t entered landfill sites, 1.47×104 t entered building materials, 2.34×104 t ended up in incineration ash, and 4.50 t were directly dumped or discarded. The phosphorus content of the SS of China presented a temporal trend of first increasing and then decreasing.
Keywords: bioavailable phosphorus; municipal sludge; occurrence forms; phosphorus; sludge disposal.