Control Of Sludge Bulking And The Application Of Treating Calcium Salt Wastewater By Activated Sludge Process

In activated sludge process， both odour and filamentous bulking occursinevitably. Two series of simulated A²/O process are to be designed and run in thisstudy, one as control （reactor1） without adding the PFS, another one （reactor2） asthe test system with PFS addition; The mechanisms of PFS added to the primarysetting tank and aeration tank to reduce the odour formation and the bulking, andenhance the P removal were studied. The results showed that the effluent qualityindex（include COD、 NH4-N、T-N and T-P） was not affected by PFS dosingï¼›Compared with the flocs in reactor1, the flocs in reactor2were compact, lessfilamentous and with well-defined boundaries; PFS react with dissolved sulfide inthe wastewater to form metal-sulfide precipitates, thus reducing H2S release.Many industrial sectors are likely to generate highly saline wastewater: theseinclude chemical, pharmaceutical and petroleum industries, fish caning, seafoodprocessing, meatpacking, tannery, and cheese factories. The use of seawater fortoilet flushing can also contribute to increasing salt levels in sewage. The dischargeof such wastewater containing at the same time high salinity and high organiccontent without prior treatment is known to adversely affect the aquatic life, waterpotability and agriculture. Thus, legislation is becoming more stringent and thetreatment of saline wastewater, both for organic matter and salt removal, isnowadays compulsory in many countries. Saline effluents are conventionally treatedthrough physico-chemical means. However, the costs of physico-chemical treatmentsbeing particularly high, alternative systems for the treatment of organic matter arenowadays increasingly the focus of research. Most of such systems involveanaerobic or aerobic biological treatment. Salinity is known to affect the metabolicactivity of bacteria and reducing microbial growth. Besides that, the structure andsettling properties of sludge flocs are affected by salt.Activated sludge process was used for treating calcium salt wastewater in thispaper. The settling property, variations of biofacies and COD removal rate ofactivated sludge system in different chloride and calcium concentrations werestudied. The results showed that when the COD was3500mg· L^-1, the Cl^-concentration was less than7000mg·L^-1and the Ca2+concentration was less than3940mg·L^-1, the COD remove rate was above90%. In this concentration range,vorticella, rotifer and other microbiological indicators were able to grow andreproduce, the sludge had high biological activity. When the concentration of Cl-andCa²⁺were increased to21000mg·L^-1and11800mg·L^-1, the COD remove rate was dropped to70.6%. In this concentration range, the microbiological indicators weredisappeared, halophilic bacteria began to reproduce, the sludge still had high activity.If the concentration of Cl-and Ca2+continued to rise, the COD remove rate wouldfall sharply and activated sludge system will crumble.Activated sludge process produces a great deal of calcium-containing sludgewhen dealing with calcium salt wastewater. One utilization method was put forwardon this study. The effect of fixing sulfur of the calcium-containing sludge as fixedsulfur agent was studied. So it was a fairly proper comprehensive utilization methodto use it for capturing sulfur and the ideal environmental and financial benefit willbe achieved.