Study On Micro-Oxygen Activated Sludge Characteristics With Weak Magnetic Field

The activated sludge process has been widely used because it is flexible, low in cost and without secondary pollution. However, due to its requirement of higher dissolved oxygen concentration (higher than 2.0mg/L), the operation cost was increased. The problem of sludge bulking would occur under environments with low dissolved oxygen concentration. This paper studied the physicochemical properties of activated sludge and its treatment effect in the weak magnetic environment with low dissolved oxygen concentration (lower than 1.0mg/L), hoping to provide parameters for the application of activated sludge in environments with low dissolved oxygen concentration and the reduction of operation cost.First, experiments were conducted to determine the optimal dosage of magnetic particles in activated sludge with low dissolved oxygen concentration. The results showed that a dosage of 4g/L will obviously promote the activity of microorganism with the removal rate of waste water COD_Cr reaching the peak of 93.53%.Then, with anaerobic sludge as the seed sludge, the paper examined the effect of the weak magnetic environment produced by magnetic particle on the treatment effect of weak aerophilic activated sludge as well as its physicochemical properties. The glucose solution was used to simulate the waste water to culture the sludge with the dosage of the magnetic particle being 4g/L. The result indicated that the reactor with magnetic particles had a higher COD_Cr removal rate than the one without magnetic particles. The range of variation within a period is larger. In the weak aerophilic environment, the sludge under the influence of weak magnetic field had better setting property with the average value of SVI lower than 100mL/g. In the reactor without magnetic particles, the sludge had a loose structure, poor setting property and a SVI value higher than 200mL/g. It would be very easy for it to come out of the reactor with the water. The MLSS of the sludge in the reactor with magnetic particles was obviously higher than that in the reactor without magnetic particles. The influence of the micro-magnetic field on the flocculation capability of the sludge was investigated through the testing of the indices such as the total dose of extracellular polymers (ECPs), PN/PS, flocculating ability (FA), relative hydrophobicity (RH) and surface charge (SC) and so on. The testing result showed that the existence of magnetic particles had greatly increased the sludge's flocculating ability.In the end, the impact of the pH loading shock and toxic wastewater loading shock on the weak aerophilic activated sludge system with the existence of magnetic field was tested. The result showsed that the existence of magnetic particles had given the reactor the ability to offset the impact of the pH loading shock and toxic wastewater loading shock. In addition to that, the COD_Cr removal rate, the sludge setting and flocculating performance as well as other physiochemical properties would soon return to the normal level in the recovery experiment.