Effects Of Composted Sewage Sludge On Forestland And Turfgrass And Surrounding Environment

Application of composted sewage sludge (CSS) in the forestry had a promising prospect, while there were concerns on the potential impact on environment and grass. The CSS came from a sewage sludge composting plant in Beijing, according to the fertilizer effect and the potential risks on soil, water and the growth of grass, this dissertation aimed to find the optimal ratio, which may provide theoretical and practical guide for the utilization of CSS.Soil was amended with CSS with5%,10%,15%and20%respectively. The physicochemical properties of soil amended by CSS and the growth of grass in amended soil were carried out in the greenhouse. The soil incubation experimental results showed that the amended soil had a stable pH, CSS had buffer action. In the initial60d, organic matters and the organic nitrogen were mineralized quickly, and provided a large number of available nutrients. The concentration of NO3--N in amended soil was significantly higher than that in the soil without CSS. The electric conductivity (EC) varied with the evolution of the concentration of organic matters resulted from nutrients mineralization and immobilization. The soil EC increased with the growing of CSS dosages, and the CSS ratio of20%had a potential risk of salt accumulation. The planting assays of grass showed that CSS promoted the growth of grass and the uptake of nutrient elements. The dry weight of turfgrass increased by10.21-229.95%, while the recovery rate of nutrient elements were different in different CSS ratio. The recovery rate of N, P of Tall Fescue and Ryegrass decreased with the growing of CSS dosages. The highest biomass and the greatest recovery rate of TN and TP of White Clover were seen with a dosage of10%. By synthetic analysis of biomass and the recovery rate, a CSS dosage of10%in amended soil was suggested to be suitable as soil amendment.The forestry runoff experiments were carried out at the dosage of3kg/m2. The results showed that there was N loss risk in the initial stage, while there were Pand organic matter loss risks3 months later in strong rainfall. The grass runoff experiments indicated that the nutrient element losses had relationship with the application dosage, if the dosage exceeded3kg/m, the NH4+, TN, PO43-and TP concentration in the runoff increased sharply, beyond v class of Environmental quality standards for surface water(GB3838-2002). The leachates from the soil column fertilized by0,1.5,3,6,12kg/m2in the surface were tested. The results showed that the leachates had the highest nitrate with the CSS dosage of6kg/m, which had the risk of nitrate pollution to groundwater. Leachates had higher TPwith the dosage of6and12kg/m2. Based on the content of nutrients in runoff and the leachates, fertilizing in summer should be avoided and the dosage should be limited at the dosage of3kg/m2.