Research On The Effect And Mechanism Of Teamwork Of Cationic Conditioner And Polyelectrolyte On The Dewater Ability Of Activated Sludge

Currently, approximately 10,000,000 tons of sludge are produced annually in the water treatment plants of China. This amount is expected to increase significantly due to the increasing demand for better quality water. How to enhance the dewater ability of sludge and reduce the cost of sludge treatment becomes an important research interest in the world.For years, polyelectrolyte conditioning has been the most popular practice for improving the dewatering property of sludge. Despite its efficiency in sludge conditioning, there is still a large quantity of water in the flocculating constituent of activated sludge, which leads to the difficulty in further reducing the water content of dewatered sludge. Many researchers have been searching for alternatives in reducing sludge water content. With the purpose of removing the water in the sludge flocs, study their effects on the sludge flocs characteristics (such as: floc size, fractal dimension, floc strength and chemical composition of sludge flocs) and dewater ability of activated sludge (such as: CST, SRF, bound water content in sludge, settling rate, water content in filtrated cake ) study from the following two aspects:1. synthesize new type of conditioner,. The mechanism of self-synthesized conditioner can be illustrated by Laplace-Young equation, in the activated sludge system, such conditioners can decrease the surface tension between vapor/liquid interfaces, and increase the solid/liquid contact angle, and increase the capillary radius, so that they can improve the activated sludge dewater ability. Conditioners can be adsorbed on activated sludge surface depending on electrostatic attraction and hydrophobic association, changing the distribution of extracellular polymeric substances (EPS) on floc surface. With the increasing of conditioners dosage, compositions of EPS were continuously released from the sludge surface and dissolved in the solution, which resulted in a series of changes of the sludge flocs characteristics, including the reduction of flocs size and increasing of relative hydrophobic. Anyhow, all the changes for the characteristics of sludge flocs directly caused the changes of the dewatering indexes of sludge. From the experimental results it can be seen that conditioners can significantly lower the bound water in sludge and the water content in filtrated cake, but no obvious effect on improving filterability and settle ability. When the dosage of CSC16 was 0.02g/g dry sludge, the water content in sludge cake after vacuum filtration dramatically decreased to 73.9%.2. Associate with the positive effects that self-synthesized sludge conditioner and commercial polyelectrolyte acted on activated sludge, adding different doses of conditioner and polyelectrolyte in activated sludge. With contrast to adding polyelectrolyte only, the experiments show that when adding polyelectrolyte, the sludge flocs would re-flocculate with a great deal of water, but this water can be removed easily. When adding 0.01g/g DS of conditioner and 0.0075g/g DS of polyelectrolyte, the water content in the remaining sludge cake after filtration decreased to 72.3%, and the sludge is more compact and dewatered comparing to the addition of one of them single at random.