The objectives of this study were to evaluate the removal characteristics of total nitrogen, the influence factor of denitrification and the optimum operating condition in the pigment wastewater treatment using PAC-A/O process. The operating conditions of PAC-A/O process were mean BOD volumetric loading 0.86 kgBOD/m3/day, mean F/M ratio 0.072∼0.13 kgBOD/kgMLVSS/day and mean C/N ratio 3.47, respectively. The conditions of anoxic process in the field plant test were mean pH 8.3∼8.7 and mean temperature 34.1~44.0℃. The ORP bending point knee was eventually appeared in the ORP -107 mV and NO3 --N removal efficiency was increased according to the ORP decrease. In the ORP -107 mV below condition, the removal efficiency of T-N and NO3 --N was 92.3∼95.0% and 98.5∼99.7%. Denitrification rate was calculated to be 1.581∼1.791 mg NO3 --N/gMLSS/hr. The experimental results showed that the ORP control in the PAC-A/O process could be an effective method for treatment of pigment wastewater.

Wastewater from the pigment industry has high levels of organics and is known as hardly biodegradable. The objective of this study is to evaluate the applicability of aerobic fixed-bed biofilm reactor packed with ceramic support carrier for the pigment wastewater treatment. Orange 2(widely used azo pigment) adsorption experiment onto biofilm and activated sludge, and continuous treatment experiments were performed. In batch adsorption experiment, maximum adsorption quantity of biofilm was at least two times higher than that of activated sludge. In continuous experiment using aerobic fixed-bed biofilm reactor, the influent concentration of COD and Orange 2 were 75∼500㎎/ℓ(0.45∼3.00㎏ COD/㎥.day), 5∼50㎎/ℓ (0.03-0.30㎏ Orange 2/㎥.day), respectively. At a COD loading rate of 2.5㎏ COD/㎥.day and Orange 2 loading rate of 0.18㎏ Orange 2/㎥.day, removal efficiency of COD and Orange 2 were over 95%, 97%, respectively.

This study was conducted to assess the characteristics of pigment wastewater and the removal rates of appropriate treatment by physical, chemical and biological process, and the possibility of reuse for effluent. Based on the results, the wastewater qualities of pigment were pH 5.1±3.4, temperature 43.0±5.0℃ BOD 1,431.4±589.6㎎/ℓ, COD 2,282.8±66.5㎎/ℓ, turbidity 1,340±82ONTU, color 243.0±147.Ounit, Pb 36.5±9.5㎎/ℓ and Cr^+6 10.3±1.3㎎/ℓ, respectively. The removal rates of adsorption by activated carbon and filter process were BOD 40.6%, COD 57.0%, turbidity 89.6%, color 87.2%, Pb 86.0% and Cr^+6 10.6%, respectively. And the removal rates of reduction, neutralization, coagulation and air floatation process were BOD 18.2%, COD 24.3%, turbidity 74.3%, color 56.7%, Pb 68.6% and Cr^+6 97.8%, respectively. The removal rates of activated sludge process were BOD 95.9%, COD 86.0%, turbidity 27.8%, color 25.2%, Pb 26.9% and Cr^+6 50.0%, respectively. The total removal rates of treatment by physical, chemical and biological process were BOD 98.0%, COD 95.4%, turbidity 98.1%, color 95.8%, Pb 97.0% and Cr^+6 99.0%, respectively. According to the test results for possibility of reuse with coagulation-adsorption by activated carbon process of effluent, COD was higher than that of raw water and others were similar to that of raw water, thus, it is considered to be reused.