Study on anti-scaling of landfill leachate treated by evaporation method.

In the mechanical vapor recompression (MVR) treatment of landfill leachate, scaling in the evaporator and heat exchanger poses a serious problem. This study explored the reasons for such scaling and proposed acid or ion-exchange pre-treatments to reduce the alkalinity of the landfill leachate nanofiltration concentrate (LLNC) to prevent scaling. The feasibility of these two methods was evaluated and the technical and economic parameters for application were obtained via experiments. A large amount of HCO3- in the LLNC was the main cause of scaling. The acid addition experiment and field application demonstrated that this method could prevent fouling problems. The cost of acid addition was USD 0.18/t. LLNC pre-treatment by ion-exchange showed that a weakly acidic cation-exchange resin performed better than a strongly acidic cation-exchange resin did. The amount of solid residue under an alkalinity of 0 mg/L could be decreased by 92.9% compared with that of raw LLNC during evaporation. Both methods could alleviate scaling and enable the wide application of the MVR evaporation process in landfill leachate treatment.

Ozonation of polyoxymethylene effluent in a rotating packed bed.

This work aimed to investigate the effectiveness of ozone in degradation of polyoxymethylene (POM) effluent in a rotating packed bed (RPB) (O3-RPB system). The degradation efficiency was evaluated in terms of chemical oxygen demand (COD), 5-day biological oxygen demand (BOD5) and BOD5/COD under various operating conditions. Pilot experiments comprising the O3-RPB unit coupled with a biological contact oxidation unit were also carried out. The COD removal rates in the pilot process increased markedly to about 70-85% compared to about 40% in the original treatment process, which is the tertiary aerobic treatment in the plant, confirming that the O3-RPB system is very efficient in improving the biodegradability of the POM effluent.

Nitrogen balance and transformation in the nitrification process of coking wastewater and the influence on nitrification kinetics.

This paper describes the total nitrogen balance, and the direction and degree of nitrogen transformation during the nitrification process of coking wastewater. According to the actual nitrification process, the conventional nitrification kinetic equation was amended. After 48 h of nitrification, the total nitrogen content remained almost the same with error less than 0.6%. The total removal efficiency of NH4(+)-N was 91.1%, in which blow-off, producing cells and transforming to nitrate nitrogen accounted for 1.1, 17.8 and 72.2% respectively. Considering the influences of NH4(+)-N blow-off and conversion from cyanide, thiocyanide and organic nitrogen, the nitrification kinetic equation was amended as µ'=0.82·S/(0.48+S).

Denitrification of coking wastewater with micro-electrolysis.

The denitrification for the coking wastewater was conducted by means of original battery principle with Fe-C micro-electrolysis. Fe-C serves as positive and negative electrodes, by which N02(-)-N and TN were reduced to nitrogen, and then the purpose of denitrifieation for coking wastewater was realized. The influences of pH value, carbon particle size, Fe/C ratio (mass ratio), reaction time and coagulation pH value on removal rate of N02(-)-N and TN were investigated. Coking wastewater originated from Jiamusi Coal Chemistry Engineering Company. The optimum conditions of treatment were as follows: the initial pH was 3.0, the dosage of Fe 73.5 g/L, reaction time 70 min, mass ratio of Fe/C ratio 1.0:1.3, coagulation pH 9.0 and sedimentation time 40 min. Under those conditions, nitrogen removal efficiencies of N02(-)-N and TN were beyond 50% and 45%, respectively.

Study on bioremediation of eutrophic lake.

Bioremediation is considered as one of the effective ways to deal with the pollution of natural water because of its high efficiency, low cost and causing no secondary pollution. The multiple microbial preparation is composed of bacteria that can transfer nutritive material harmless and some natural humic acid which can destroy algae. The qualified bacteria were selected, separated, and enriched from the water and bottom sediment of eutrophic lake. A field trial of bioremediation was carried out in 60 m(3) of eutrophic water body in Yingze Lake of Anshan for four months. TN (total nitrogen), TP (total phosphorus), ammonia nitrogen, CODCr, and turbidity of the trial water and untreated water were measured termly. Contrastive analysis showed the mulriple microbial preparation can increase the water capacity of self-purification, decrease the turbidity, inhibit algae growth and improve water quality gradually at substantially lower cost. Thus the problem of lake eutrophication can be solved radically by bioremediation.