Effects And Control Of Sludge Loading And Dissolved Oxygen On Filamentous Bulking

At home and abroad , sludge load and dissolved oxygen are considered to be two important factors affecting the growth of filament in the present study that can lead to filamentous bulking, but so many related results are in chaos. The effects of sludge load and DO on the filamentous bulking of prefabricate sewage and beer wastewater, both are typical wastewater which is easy to cause filamentous bulking, were studied systematically using SBR in which experimental conditions can be controlled flexibly and accurately. We Compared the two methods, the use of oxidizer ClO₂ and the adjustment of factor leading to bulking, that are used to control the low load sludge bulking and the low DO bulking. We also systematically studied the impact of the sludge concentration on the value of SVI.A large number of repetitive experiment showed that the filamentous bulking wouldn't be caused if the reactor was operated under the high sludge load and enough DO concentration simultaneously. The experiment results indicated that the oxygen surrounding sludge floc might be quickly consumed under high sludge load, lead to the lack of oxygen in the internal of the floc particles and massive proliferation of filamentous and sludge bulking.We summed up by the experiment under different sludge load and DO concentration and found a relationship that the concentration of DO began to cause bulking increase with the increasing of sludge load. Also if the sludge load does not become a limiting factor, low DO concentration can cause low DO bulking; if DO concentration is high enough Sludge load reduced to a certain extent will become a factor of low sludge load bulking; when DO and sludge load are low enough at the same time sludge bulking have taken place during the experiment.By increasing the factor leading to bulking to a certain value, low sludge load bulking and low DO concentration bulking can effectively be controlled after running a certain number of cycles. Such an approach is the fundamental way to solve the low sludge load bulking and the low DO concentration bulking. During the experiment, bulking sludge controled by such an approach did not bulk again in the later operation.The experiment results about the control of low sludge load bulking indicated that the cycles of the sludge bulking control decreased with the increase of sludge load. The recovery cycles no longer changed when sludge load rose to some level. We come to the same laws from experiment of control of low DO bulking under different DO concentration. Concluded that, between the impact of DO concentration on the Organic matter degradation rate and the impact of DO concentration on the control of sludge bulking may exist a certain relationship: Under a certain DO concentration, the organic matter degradation rate and the cycles of low DO bulking control are related to a negative correlation.By increasing DO and sludge load and running a certain number of cycles, low sludge load and DO bulking was effectively controlled, but SVI was unchanged by a separate increase of DO or sludge load.By adding ClO₂, low sludge load bulking and low DO bulking can be controled quickly and effectively, in a short time, SVI can be reduced to 150mg/L below. Under this experiment conditions, ClO₂ dosage of 30mg/L is the ideal dose for the removal of COD can reach a higher level after several cycles with the little effect of activated sludge treatment and sludge bulking can be controlled Quickly and effectively. But without adjustment of the factor leading to bulking, SVI will increase again after stopping adding ClO₂ and running a certain number of cycles.The experiment about the sludge concentration affecting SVI was also carried out. It was foud that the effect of the sludge concentration on SVI was very complex and varying . The experiment results indicated:①SVI increased with the growing of the sludge concentration in some sludge concentration range, but SVI decreased with the growing of the sludge concentration in other range; On the other hand, the regular pattern of SVI changing with the sludge concentration was not also identical.②Better performance of sludge settlement, the impact of sludge concentration on SVI value is little with the little margin of SVI value under different sludge concentration; with the poor performance of sludge settlement, the margin of SVI value under different sludge concentration gradually larger.