Research On The Compound Of Sludge Based On Planting Soil In The Saline-alkali Area

With the acceleration of urbanization,more and more sewage treatment plants had been constructed and used in recent years.As the by-product of wastewater treatment,the production of sewage sludge was rising year by year.More attention were paid on the whereabouts of sludge,because of the high content of organic matter,N,P,K and other nutrient elements in sludge,and sludge land utilization become the hot spot of sludge disposal.Tianjin,as one of the municipalities,the demand for land would be bigger with the rapid economic development and population influx.There is much saline-alkali soil in Tianjin because of its geographic position,so if the saline-alkali soil can be improved reasonably,the crisis of land demand would be relieved greatly.This study compounded the sewage sludge and saline-alkali soil,which could not only solve the problem of sludge disposal,but also improve the properties of saline-alkali soil.Meanwhile,it could compound the high quality of soil for plant cultivation.The appropriate range of distribution was studied based on the physical and chemical properties of the compound soil based on the control plant soil,also the influence of planting experiment on the physical and chemical properties was researched,at last the optimization of electrical conductivity was studied.The analysis of the physical and chemical properties of compound soil showed that: the best dry addition amount of aerobic composted sludge,anaerobic nitrated sludge,raw sludge was 20%~30%,20%~30%,30%~40% respectively.All the physical and chemical properties of these compound soil could basically meet the standard of green planting soil,and were close to the control soil.However the electrical conductivity of compound soil was excessive.The analysis of the plant experiment of alfalfa showed that: the germination effect was better in the saline-alkali soil,but not conducive to the growth;the compound soil of dry aerobic composted sludge dosage of 10% and 20% were good for plant growth,in which the dosage of 20% was better,even better than the control soil;Anaerobic nitrated sludge and its compound soil were good for alfalfa germination,but the alfalfa grew badly and all died in the end;the alfalfa could not live on the raw sludge and its compound soil.The analysis of the properties of compound soil before and after planting showed that: the plating was benefit for the improvement of soil properties,which was influenced by the plant activity,regular watering and ploughing.The bulk density,total porosity,capillary property,content of maximum moisture and electrical conductivity of the compound soil of dry aerobic composted sludge addition of 10% and 20% were improved after planting.The analysis of the optimal experiment of electrical conductivity of the compound soil of dry aerobic composted sludge dosage of 10%,20% and 30%showed that: the electrical conductivity all decreased after adding natural zeolite and attapulgite.The optimum adding amount of zeolite and attapulgite was 6%(w/w)and5%(w/w)respectively,and the effect of natural zeolite was better than attpulgite.