Feasibility of Land Application of Sewage Sludge from Kunming Wastewater Treatment Plants

The organic matter and nutrients in sewage sludge from six wastewater treatment plants in Kunming City were investigated,and a comparison of the investigation results with the average values in sewage sludge from domestic WWTPs and farmyard manure was made.The results show that the organic matter,nitrogen,phosphorus and potassium in sewage sludge from the six wastewater treatment plants are 50.1% to 57.2%,2.10% to 2.93%,1.53% to 2.77% and 0.53% to 1.02% respectively.As a whole,the organic matter,nitrogen and phosphorus in sewage sludge from these plants are richer,the potential of sludge land application is higher,and it is an organic manure source that merits a reasonable application.However,due to the influence of heavy metals in the sludge,only the sludge from the first,second and fifth WWTPs can be used on land,but it needs safe treatment before application.The sludge from the third,fourth and sixth WWTPs can not be used on land for the concentrations of heavy metals which seriously exceed the standard,especially the sludge from the third WWTP can not even be disposed as the cover material for landfill site after drying.