مجله آب و فاضلاب
پیاپی 39 (پاییز 1380)

One of the operational problems which arises in the most activated sludge treatment plants, is poor settling and compaction of activated sludge in the secondary sedimentation tank. Poor settleability of activated sludge causes not only deterioration of final effluent quality, but also the sludge bulk increase and consequently led to an increase in sludge processing costs. In this research that was performed in the Shahrake-Ghods (Gharb) wastewater treatment plant, the quantity and quality of the influent raw sewage to the wastewater treatment plant, the causes of poor settling of sludge and its inadequate compaction in the secondary sedimentation tank, the quality of final effluent and the efficiency of treatment plant in experimental method have been examined. Microscopic observations revealed that, the bulking causative bacteria in the plant are the M. Parvicella and 0041 type abundance respectively.Growing of these filamentous bacteria probably due to low food to microorganism ratio (F/M=0.13d-1), limited dissolved oxygen concentration (Do<2mg/l) and completely mixed hydraulic regime (dN=1.32) in the Shahrak-e-Ghods plant aeration tank.The other factors created filamentous bulking in the treatment plant are as follow:The presence of primary sedimentation tank and also discharging the industrial wastewater, specially discharging the sewage of blood treatment center, discharging the supernatant from the inadequate thickening and stabilization of the sludge and also, discharging the drainage resulting from drying beds into the influent raw sewage, specially during time of peak flow through creating organic loading shock and increasing demand to dissolved oxygen in aeration tank and finally at this stage, the principles of designing and operation of treatment plant were checked and in the forth stage, the quality of final effluent and efficiency of treatment plant were investigated.

Tehran’s annual drinking water consumption is 2.5 times higher than that of the last 24 years (1976-1999), while the population has increased only 1.5 fold. Due to Tehran’s special geographic conditions and, in case such increasing trend continues, there remains no alternative but transferring water from long distances which cost a lot.Therefore study and modeling of the factors, which affect consumption, in order to control and design optimal consumption pattern will be of special importance.In this paper, distribution of maximum and minimum temperature is presented as the “Temperature Indicator “. Then Tehran’s water consumption modeled by analysis of variance and determining effective factors.

In metal machining, a fluid is required to both lubricate and cool the tool and work piece. In many operations the fluid used is an oil water emulsion. During use it can not be discharged to most sewers (because of high COD and BOD). Their effluents could cause undesirable environmental effects. The oil forms the microemulsion (O/W) with water in different proportions. This is made possible by the aid of surfactants. Inversely, the addition of electrolyts cause the breakage of microemulsion. In this case, it is possible to separate aqueous phase from organic phase. This separation can decrease 98% of COD and BOD. The adaptability of this process to large and small scale applications should be very interesting for countries such as Iran where is in lack of sewage system, and industrial companies are usually situated in the urban areas.This paper describe the type of laboratory tests for the treatment of these effluents. During the test, effects of different electrolyts (HCl, H2SO4, NaCl, MgSO4. 7(H2O), FeCL3, Al2(SO4)3. 18(H2O) and their concentrations on breakage of microemulsion, was determined. The achieved results showed that mechanisms responsible for destablization of colloids depend to the valence of the ions having a charge opposite to that of the colloid and separation of these phases (Oil-Water) can reduce the pollution about 98%.

Aerobic Sequencing Batch Reactor (SBR) experiments in the bench scale was investigated to study the treatability of wastewater from milk factory. The reactor was fed with milk factory and synthetic wastewater under different operation conditions. The COD removal efficiency was achieved more than 90%. The optimum oxygen in the reactor was found to be 2 to 3 mg/l. The study demonstrates that the capability of aeration SBR for removed of COD from industrial wastewater.

Stabilization ponds have recently attracted more attention as a natural wastewater treatment method and are currently being used in almost all developed and developing countries across the globe. The technical, economic, energy saving, and operational advantages of such treatment systems have motivated many researchers in these countries to study the improvement of stabilization ponds in order to increase their efficiency and also to lift the difficulties in their operation.In this investigation the rate of dissolved oxygen fluctuation and pH in facultative ponds at different situations were studied. The results showed the maximum oxygen concentration was increased up to 30 mg/l.The oxygen concentrations at different depth and length were varied. The pH was changed over the period of day and night the maximum value reached up to ten.

Effluent of power plant’s boilers always contains som elements such as Al, Ca, Co, Mg, Cr, Cu, Fe, Si, Mn, Mo, Na, Ni, K, V and Zn. This is due to chemical cleaning and recycling of water and consequent corrosion.Discharge of untreat wastewater may cause sever adverse effects on environment and human being.In this study the concentration of these elements in the wastewater at different places in Neka’s Power Plant were determined. The analysis of the fuel combustion and the deposits from chemical cleaning of the outer surfaces of boiler pipes and preheater showed the existence of V, Fe, Na, Ni, K, Zn, Cu, Cr and Co. The amount of V. in deposits was 60.0-70.0ppm which is higher than the standard limit.The analysis of the deposits from chemical cleaning of the inner side of the boiler pipes, condensors, stator water filter and gas turbine units showed the existence of Al, Ca, Co, Cr, Cu, Fe, Ni. Zn, Si and Na. The amount of Cu in the samples was found 90.0ppm which was much more than the standard limit (3.0ppm).The analysis of the wastewater of the chemical cleaning, ionic exchangers, sandfilters, chlorination cells and the final wastewater showed the existence of Al, Ca, Mg, Cu, Fe, Mn, Mo, Ni, Zn, Si, Na and K. However, these amount were less than the standard limit. The concentration of the sulfate in the final wastewater was found 4016. ppm.

The average annual precipitation in Iran is only about 250 mm and the performance of other factors involved does not allow for the losses in our reservoirs to be compensated for.Climatic conditions, spatial and temporal distribution of precipitation, increasing water use, disproportionate withdrawals in violation of laws and regulations for the equitable use and distribution of water are the causes for the water crisis Iran is facing and the great danger our groundwater resources are encountering.Investigations on the ground water resources in Borkhar plain in Isfahan show an annual withdrawal of 45 MCM in excess of the quantity the resources can provide. This rate of water withdrawal has caused a corresponding annual decline of 0.5 meter in the aquifer water level. This is while the inflow from neighboring basins and from branching channel from the Zayandeh Rood River have been recharging the aquifer.