Feasibility study on EO/EG wastewater treatment using pilot scale SBR

The sequencing batch reactors were developed to treat the actual wastewater from ethylene glycol/ethylene oxide producing industry. Four identical reactors with total and effective liquid volumes of 9 and 7 L were operated respectively in parallel. Laboratory experiments were conducted with different organic loadings of 500, 1000, 1500 and 3000 g-COD/m[3]. day and the performance of the reactors was studied under different sludge ages of 10, 20 and 30 days, the kinetic constants at optimal operational conditions were also determined. According to the results, the efficient removal of COD was 79.5 and 83.5% [SRT = 20 days] and 86% [SRT = 30 days] for SBR 1 and 2 respectively [OLR = 0.5 to 1 kg-COD/m[3]. day] with required reaction time of about 17 h. In order to reach the COD removal efficiencies over 86% at higher OLR values, the researchers required longer reaction periods about 34.5 h for SBR 3 and 4. However, the SRT values have no significant effects on the performance of SBR 1 and 2 at the aeration times greater than 22.5 h while in the case of reactors 3 and 4, with an increase on SRT at all aeration times, the COD removal efficiency increased. It is concluded that the system used in the present study could show an acceptable stability and performance in the treatment of the wastewater containing high concentrations of organic matters especially from EO/EG industries

[Heterotrophic bacteria in drinking water in Tabriz, Iran]

Recently the use of heterotrophic plate count [HPC] has received much attention as a supplementary indicator of the MPN test in water quality control. The US Environmental Protection Agency [USEPA] has declared 500 cfu/mL as the maximum acceptable level for heterotrophic bacteria in distribution networks. Currently the HPC determination is not among the routine control items in Tabriz city and there is no published information on the presence of heterotrophic bacteria in that city's potable water. In this study the presence of HPC in potable water main was determined in Tabriz city, Iran. A total of 50 water samples, representing drinking water of the whole city of Tabriz, were taken randomly from different districts of Tabriz city and their HPC, coliform, residual chlorine, turbidity, temperature, and pH were measured. For the heterotrophic bacteria the R2A and Nutrients Agar culture media were used, while the spread plate count method was used for the HPC test. The statistical tests used for data analysis were the t-test and regression. In 50% of the samples heterotrophic bacteria were present. In 6 districts the HPC was higher than 500 cfu/mL. Based on Nutrient Agar and R2A, the HPC indicator in Tabriz drinking water was 184 +/- 340 and 154 +/- 315 cfu/mL, respectively, the growth rate being higher in the former medium. There was a significant correlation between the HPC and residual chlorine in both media [for Nutrients Agar, p<0.05; R= -0.347, and for R2A, p<0.05; R= -0.312]. Also, there was a significant positive correlation between the HPC and pH [p<0.05]. Further analysis of the data showed that the correlation between HPC values in both media was also significant [p<0.95, R= 0.95]. The presence of heterotrophic bacteria in 50% of the water samples tested indicates that drinking water contamination with these bacteria is a public health problem in Tabriz city. As a result, monitoring of HPC at least once every 6 or, at least, 12 months, together with coliform bacteria, and the comparison of the results over time can help to better determine water quality in the distribution system, as well as boost the system operation and ensure drinking water with a high quality

Performance of aerated submerged fixed-film bioreactor for treatment of acrylonitrile-containing wastewater

Acrylonitrile is used as the main raw material for manufacturing acrylonitrile butadiene styrene resin. It is usually found as pollutant in the petrochemical wastewater. In this research an aerated submerged fixed-film reactor was developed to treat a synthetic acrylonitrile butadiene styrene unit wastewater containing acrylonitrile. Laboratory experiments were conducted using a bioreactor with 44.2 L capacity operated at different hydraulic and organic loading rates. Stationary submerged biofilms were attached to net-type media [polypropylene] under diffused aeration. The specific surface area and porosity of media were 324 m[2]/m[3] and 87%, respectively. In the first phase the reactor was operated in hydraulic retention times of 9, 7, 5 and 4 h with soluble chemical oxygen demand of 300 mg/L. Then the experiments were continued with the constant retention time of 4 h and variable chemical oxygen demand concentrations of 350, 400 and 450 mg/L. In stable condition of operation and loading rates of 0.8 to 2.4 kg/m[3]d the removal efficiencies of reactor for soluble chemical oxygen demand reached to 95 to 99%. At the organic loading rate up to 2.4 kg/m[3]d the soluble chemical oxygen demand was less than 50 mg/L which was lower than the Iranian national discharge standards [chemical oxygen demand<60 mg/L]. The increase of organic and surface loading to 2.7 kg/m3d and 23.16 g/m[2]d, respectively, caused the system becoming unstable and the soluble chemical oxygen demand removal efficiency decreased to 66%. Finally, the kinetic coefficients of the aerated submerged fixed-film reactor for treating of acrylonitrile were determined using a separate pilot unit. According to the results, it was concluded that the aerated submerged fixed-film reactor can be used as suitable approaches for treating of petrochemical effluents contain acrylonitrile