In the dairy industry mild steel is used as the construction material for the effluent treatment plants, pipelines, reinforcement in concrete structures etc. The steel exposed to the dairy effluent faces corrosion due to the microbes. In the present study the role of microbes in dairy effluent on the corrosion of mild steel has been investigated. Pseudomonas sp., Streptococcus sp., Micrococcus sp., Bacillus sp., Neisseria sp. and Lactobacillus sp. were identified in dairy effluent. Corrosion rate has been estimated by weight loss measurements and polarization technique. The Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD) studies were found helpful in investigating the chemical pathway leading to the formation of corrosion products on the mild steel during fermentation. Initiation of pitting corrosion was noticed on steel specimens by scanning electron microscope (SEM). A mechanism has been proposed for microbiologically influenced corrosion in dairy effluent.

Two UASB reactors R-I and R-II, each of 10liters capacity, made up of acryl material were operated parallel and continuously for a period of 220 days, using actual effluent of the NSSC pulp and paper mill, at mesophilic temperature and neutral pH. The main objective was to investigate the treatability performance of the reactors at varying OLR and HRT in terms of TOC and lignin removal. The reactor R-I was used by conventional procedure, whereas, for the reactor R-II methanol and activated carbon was added to supplement its efficiency. Corresponding to an optimum OLR of 4.5kg/m3-day and HRT of 18hrs, the reactor R-II gives 69% TOC and 60% lignin removal. But, in the reactor R-I at same operating conditions, only 56% TOC and 51% lignin removal was noticed. However, the biogas yield in the reactor R-I was noticed relatively more than in the R-II. The biogas yield observed was 0.28m3/kg-CODrem and 0.18m3/kg-CODrem in the reactor R-I and R-II, respectively, with 56-58% methane content in both the reactors. The average VFAs concentration observed in the reactor R-I and R-II is 360mg/L and 230mg/L, respectively. The results of this study suggest that the use of methanol and activated carbon to enhance the treatability efficiency of the UASB reactor is a viable option for the treatment of NSSC pulping effluent.

Chemical oxidation is one of the most suitable treatment methods for reducing organic pollutants and the number of pathogens remaining in secondary effluents. Ozone is the most powerful oxidizing agent commonly used because of its many advantages over chlorination. In this study the efficiency of ozonation in advanced wastewater treatment of Sahebgharanieh Plant has been determined. Ozone generation has been performed by irradiation of compressed air with 4 special UV lamps. The total output of these lamps was determined to be 0.74 mg ozone per minute at established conditions. Considering 3 periods of ozonation of effluent samples (30, 60 and 120 min) and ozone transfer coefficient of 95%, the concentrations of applied ozone for wastewater treatment were specified to be 10.5, 21 and 42 mg/l, respectively. Ozonation of secondary effluents at these periods has resulted in 17, 24 and 30 percent reduction in average COD and about 20, 18 and 32 percent decrease in BOD5. It is believed that the 2 percent increase observed in BOD after 30 minutes is caused by changing some amount of COD to BOD5 by applied ozone. According to the prescribed reduction values it could be concluded that the final effluent of a typical treatment plant would become better qualified for water reuse in irrigation. But it should be declared that the effluent might not be completely disinfected irrespective of about 99.0% decrease determined in MPN of total coliforms. Also it must be noted that this degree of disinfection was accomplished only for 62.5% of samples. Ozonation of effluent samples has caused an increase in pH value which was at least 0.4 of a pH unit.