Practice of High Concentration Sludge for Efficient Nutrient Removal from Municipal Sewage

ECOSUNIDE is a new activated sludge process based on the sludge concentration optimization theory.With it,we carried out a high sludge concentration by changing influent mode and distributing carbon source in a reasonable way,which can improve the ecological superiority of nitrification and denitrification for the growth of phosphorous accumulating organisms(PAOs)and nitrifiers and raised the nutrient removal efficiency of municipal sewage treatment plants.In 2007,we adopted this technique in Linyi Sewage Treatment Plant in Shandong Province,China.After the reconstruction,we achieved the high efficiency of nutrient removal with low investment under the dynamic load of the secondary sewage treatment plant.The effluent water qualities meet the classⅠ-A criteria specified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant(GB 18918-2002)and the rest effluent indexes meet the classⅠ-B criteria.Besides,we have above 20% operating cost cut by stopping the internal reflux without power charge increased and any new pool structures built.

The Unified Dynamic Theory and Its Engineering Research

The unified dynamic theory reveals the substrate-based nonlinear growth phenomena. It means that the environment of high organism concentration and low substrate state is useful for the growth of weak floras. With ecological superior nitrification denltrification （ ECOSUNIDE ） technology, high sludge concentration by distributing influent to anaerobic and anoxic zones is carried out, and the ecological superiorities of nitrifiers, denitrifiers, and phosphate accumulating organisms （PAOs） get to be promoted. One of the anaerobic/anoxic/oxic（A/A/O） treatment lines of a sewage treatment plant with ECOSUNIDE technology for further investigation on the nutrient removal efficiency is reformed. The advantages of ECOSUNIDE, such as high efficiency and saving energy, are well demonstrated, even under the condition of low temperature （about 15℃） and carbon-resource （C/N ratio lower than 2. 5 ）. In ECOSUNIDE system, the effluent indexes as biochemical oxygen demand （BOD）, chemical oxygen demand （COD）, and NH3--N reach the Class I-A criteria specified in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant （ GB18918-2002 ）, and suspended substance （ SS ）, total nitrogen （TN）, and total phosphorus（TP） meet the Class I -B criteria. While the effluent qualities of A/A/O system only reach the secondary discharge standard. Through the comparison on the sludge character of ECOSUNH）E system with A/A/O, more abundant biofacies, darker and more intense zoogloea, more obvious filamentous bacterium, and clearer floes edges in ECOSUNIDE system are found.

Simultaneous nitrogen and phosphorus removal under low dissolved oxygen conditions

A full-scale test was operated by using low dissolved oxygen activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of CODCr, TN and TP varied in a range of 352.9 mg/L-1338.2 mg/L, 34.4 mg/L-96.3 mg/L, and 2.21 mg/L-24.0 mg/L, the average removal efficiencies were 94.9%, 86.7% and 93.0%, respectively. During the test period of two months, effluent meas of CODCr,, BOD5, NH3-N, TN and TP were below 50 mg/L, 25 mg/L, 10 mg/L and 1.0 mg/L respectively. The low dissolved oxygen activated sludge process has a simple flow sheet, fewer facilities and high N and P removal efficiency. It is very convenient to retrofit the conventional activated sludge process with the above process.

Nitrogen and phosphorus removal under intermittent aeration conditions

A practice wastewater treatment plant was operated using intermittent aeration activated sludge process to enhance biological nitrogen and phosphorus removal. When the influent concentrations of COD Cr , BOD 5, TN, TP, NH 3\|N, TKN, and SS varied in a range of 207.5—1640 mg/L, 61.8—637 mg/L, 28.5—75.6 mg/L, 4.38—20.2 mg/L, 13.6—31.9 mg/L, 28.5—75.6 mg/L, and 111—1208 mg/L, the effluent means were less than 50 mg/L, 20 mg/L, 5 mg/L, 1.0 mg/L, 5 mg/L, 10 mg/L, and 20 mg/L, respectively. Based on a long time of operating results, this process is very suitable for nutrient biological removal for treating the municipal wastewater those water characteristics are similar as that of the Songjiang Municipal Waste Water Treatment Plant(SJMWTP).