Study On Treatment Of Mid-stage Pulping Effluent By Aerobic Activated Sludge In The Presence Of Fe³⁺

The effluent of wastewater pretreatment, such as ferrous flocculant and Fentonoxidation often contain iron ions, which has impact on the subsequent aerobicbiochemical treatment. In this paper, the treatment of mid-stage pulping effluent byaerobic activated sludge in the presence of iron ions was studied, expecting to provideparameters for the treatment process.First of all, optimal dosing of iron ions was determined through the experiment,the results showed it had promoting effect on microorganisms when the iron ionsdosage was30mg/L, and CODcr removal efficiency of simulated wastewater reached88.21%.Then, mid-stage pulping effluent was used to domesticate the aerobic activatedsludge with the iron ions addition of30mg/L, and the blank control group without ironions was set. In domestication process, the ratio of mid-stage pulping effluent to thenutrient solution improved constantly, until100%mid-stage pulping effluent. Theentire process of domestication, COD and UV-254removal efficiency of the reactorwith iron were higher than that of the blank control reactor, when the domesticationwas end, COD removal efficiency of the two reactors were78.2%and78.2%respectively, UV-254removal efficiency were50.0%and37.7%, respectively.By the analysis of the dehydrogenase activity and MLSS, activity of the sludge inthe reactor with iron ions was higher than that of the blank control reactor. By theanalysis of the SVI value, amount of extracellular polymer and the ratio of the PN/PSin extracellular polymers, the sludge settling performance and flocculation ability inthe reactor with iron were superior to that of the blank control reactor. Effects of pH and the DO concentration on treatment of pulping wastewater byaerobic activated sludge were investigated in the presence of iron ions. The resultsshowed that when pH was in neutral range, DO concentration was2.0mg/L, goodtreatment effect achieved, and the physicochemical properties of sludge were better. Inthe given range of pH and the DO concentration, the treatment effect, the sludgeactivity and physicochemical properties with iron were better than that of the blankcontrol group.Finally, effects of pH and the DO concentration shock on the activated sludgesystem with iron ions were studied, the results showed that the reactor with Fe3+hadgood resistance ability to pH and DO concentration shock, and in the recoveryexperiments, water quality and the sludge settling performance could recover tonormal levels in short time.