The fraction of extractable extracellular polymeric substances (EPS) and the shear sensitivity (k(ss)) are key parameters with respect to sludge dewatering, affecting the dry matter content of dewatered sludge and the dewatering rate and conditioner demand, respectively. Methods are described for determination of the two key parameters by use of the same laboratory test reactor. The implications of such characterisation with respect to dewatering are discussed based on examples of application to sludge processing and novel process development for sludge minimisation.
A side effect of the application of chlorine for controlling filamentous bulking is deflocculation of floc‐forming bacteria, which may cause unacceptable effluent deterioration depending on dosing. It was assumed that chlorine may adversely affect the adhesion ability of floc bacteria, promoting their erosion in shear flow. The effect of chlorination on the strength of activated sludge flocs was investigated. The adhesion–erosion (AE) model developed by Mikkelsen and Keiding was used to interpret results from deflocculation tests with varying shear and solids concentration. The AE model yields the adhesion enthalpy (δHG/R) of cells in sludge flocs and parameters from the model were used to quantify the sludge in terms of floc strength. Two activated sludges with different initial characteristics were studied. The resulting model parameters showed that the AE model was suitable for quantifying the bond energy of particles to the activated sludge exposed to chlorine. For one activated sludge, adhesion of cells was largely unaffected by the applied chlorine doses. A second sludge showed reduced adhesion strength with chlorine, leading to increasing deflocculation. The simple batch test and AE model proved valuable for assessing the effect of chlorination on the flocs in activated sludge. By use of these procedures, it is possible to determine acceptable chlorine dosing to avoid excessive deflocculation and effluent deterioration.
The increase in the costs of water and wastewater treatment makes it relevant to develop tools that allow the efficient use of water in the industry, aiming at reduce costs and respecting the disposal limits imposed by the legislation. Thus, the objective of this work is to apply an integrated methodology for the synthesis and analysis of water networks and industrial wastewaters, combining the Wastewater Sources Diagram (WWSD) method with the results of the Water Sources Diagram (WSD) to the data representative of the pulp and paper industry. A case study considering the relevant contaminants present in the wastewaters from this process was carried out. The wastewater treatment network generated with the WWSD reduced the need for wastewater treatment by 35.20%, allowing lower costs and environmental impacts.
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