Influence Of The Operating Conditions On Sludge Dewaterability In Sludge Chemical Conditioning

Municipal and industrial wastewater treatment plants produce large amounts of waste sludge. The content of water in the sludge can account for ranging from 95 to 99 percent, therefore the removal of moisture can greatly reduce the volume of sludge in order to further dispose. It is well known that the activated sludge is very difficult to dewater because most of colloid particles in sludge take electric charge, therefore the enhancement of dewaterability becomes an important topic.The way of sludge physical or chemical conditioning can change physical and chemical nature of colloid particles and destroy the sludge colloid structure and also reduce the affinity between water and colloid particles, thus the dewaterability of sludge can be improved in the practice. The medicament conditioning becomes a common method as a result of simple operation and good effects. However there are many factors which affect sludge dewaterability in the sludge conditioning.Sludge dewaterability is estimated from specific resistance to filtration in this paper. The paper studies that some factors such as concentration of pharmaceutical and the way of adding pharmaceutical and the temperature and pH value have influences on sludge dewaterability in sludge conditioning. The paper also determines the extent of influences according to experiment and provides reference material for the actual production.The paper designs to make combined use of inorganic and organic high molecular polymer in sludge conditioning because when we use inorganic flocculant alone the dosage is large and the effect is not good, while the content of moisture in sludge cake is high using organic high molecular polymer alone. The paper takes specific resistance to filtration as the main index of dewaterability and studies the influence of some controllable factors on sludge dewaterability in sludge conditioning of two schemes—one is combined use of PAM and PAC and another is combined use of PAM and PFS. As far as the cost of pharmaceutical is concerned the cost in combined use of inorganic and organic high molecular polymer is less than the cost of using organic high molecular polymer alone. When we make combined use of inorganic and organic high molecular polymer, the better way of adding pharmaceutical must be choosed by on-the-spot experiment on the basis of the sludge nature. It is not sure to have good effect that we add inorganic flocculant first. Whenwe make combined use of inorganic and organic high molecular polymer, the specific resistance to filtration is smaller and the solid rate of sludge cake is higher.The paper compares three schemes(PAM alone, combined use of PAM and PAC and combined use of PAM and PFS)from five aspects-the settlement, specific resistance to filtration, suspended solid, COD and solid rate of sludge cake. Three schemes have merits and demerits respectively.Finally the paper attempts to discover the relations between the index of sludge nature and the optimal dosage of using PAM alone. It shows that the optimal dosage of PAM increases along with the increase of the solid rate of sludge, but the relation is not the linear one.