WATER AND WASTEWATER
Year:2008 | Volume:19 | Issue:2 (66)|Papers Count:12

Horizontal roughing filters (HRF) can properly remove suspended solids and microorganisms from surface waters if they operate at filtration rates below 1.5 m/h. These filters are common raw water pre-treatment before slow sand filters. This study was conducted by installing an HRF pilot system on effluent pumping station city of Qom wastewater treatment plant based on the aerated lagoon process. The pilot was a horizontal cylindrical column consisting of three compartments filled with river gravel of various sizes. Grab samples were simultaneously taken from inlet and outlet of the HRF at three filtration rates: 0.5, 1, and 1.5 m/h. Total and fecal coliforms were tested according to standard methods for water and wastewater tests. Results indicated that filtration rate had a significant effect on the amounts of total and fecal coliforms in HRF effluent. For the HRF steady-state operation, average total coliform removal efficiency for all filtration rates was higher than 87 percent.

Landfill leach ate is one of the most contaminated wastewaters. Because of the widespread use of municipal landfills for final disposal of solid waste, there is an increasing concern over their public health and environmental hazards. In this study, the landfill leach ate of city of Shiraz was successfully treated using an ABR system of 4 compartments with a capacity of 64 litters volume and a hydraulic retention time of 4 days. COD removal efficiencies of 82.38, 85.19, 82.53, 82.22, and 80.12 per cent were achieved for organic loading rates (OLR) of 1.2, 2, 3, 5, and 7.75 kg COD/m3/day, respectively. Sampling and test results revealed that the highest activity of acid genesis bacteria belonged to the 1st compartment with the least amount of pH=6.54. It was shown that due to the formation of ammonia alkalinity in the reactor, there was a slight increase in the alkalinity of leach ate with the maximum effluent amount of 6291 mg/l (as CaCO3) in OLR=7.75 kg COD/m3/day. In this study, hydrodynamic characteristics and biological performance of an anaerobic baffled reactor (ABR) was also investigated. Residence time distribution (RTD) test with step input method was carried out on ABR. According to the graphs and theoretical model results, the number of CFSTRs was equal to the number of the ABR compartments (N=4).

Phenol is one of the most common compounds found in many industrial effluents such as petroleum refining and petrochemicals, pharmaceuticals, pesticides, paint and dye industries, organic chemicals manufacturing, etc. The contamination of bodies of water with phenol is a serious problem in terms of environmental considerations due to its high toxicity. In this study, toxicity of phenol and its degradation mixtures by sonochemical, photochemical, and photosonochemical processes were investigated. Toxicity assay tests were carried out using Daphnia magna as a bio-indicator. The sonochemical and photochemical experiments were carried out using a bath sonicator (500 W) working at 35 and 130 kHz frequencies and with a 400 W medium pressure mercury lamp, respectively. Experiments were performed at initial concentrations of 100 mg L-1. Bioassay tests showed that phenol was toxic to D.magna and so resulted in quite low LC50 values. Comparison of toxicity units (TU) between phenol and effluent toxicity showed that TU value for photosonochemical effluent was lower than that obtained for phenol, photochemical effluent, and sonochemical effluent. It was found that the toxicity unit of photochemical effluent was lower than that obtained for sonochemical effluent. According to the D.magna acute toxicity test, it is concluded that photosonolysis and photolysis are capable of decreasing the toxicity of by-products formed during the degradation of phenol aqueous solutions. Photosonic and photolytic processes can, therefore, be recommended as a potential approach to the treatment of phenolic wastewater.

Discharge of agricultural and industrial effluents into surface water resources cause water quality degradation. The swan mussel (Anodonta cygnea) is one of the most important fresh water suspension feeders that can be used for the purpose of pollutant reduction. In order to evaluate the capability of A. cygnea in the reduction of nitrates and phosphates in municipal wastewater, several breeds & Rhyter culture medium were investigated. The results obtained from the open system showed that the growing fresh algae were capable of removing a considerable portion of the dissolved materials. The combined system of mussels and algae had an average nitrate removal efficiency of 76.3% and a phosphate removal efficiency of 75.3%. Based on our results, this breed of mussels may be recommended as a crucial organism in biological wastewater treatment.

The increasing trend in (urban) water demand due to population growth places a growing stress on available water resources and calls for an efficient and acceptable long-term management of the resources. Hence, application of multi-attribute decision-making systems is essential for evaluating urban water supply schemes. A number of multi-attribute decision-making methods have been developed. This paper aims to survey the application of such systems to urban water supply problems and the effects of each multi-attribute decision-making method selected on the final ranking of alternatives. Three methods of Induced Ordered Weighted Averaging (IOWA), Linear Assignment (LA), and TOPSIS have been considered for a real urban water management case study in the city of Zahedan in Iran. The results revealed that the multi-attribute decision-making method selected had a considerable effect on the final ranking of a finite set of alternatives such that different MADM techniques yielded different results for the same problem. It is, therefore, necessary to select the method according to the specific characteristics of the problem at hand, type of data available, and the assessments made. The ultimate alternative must be, thus, selected once evaluations have been made of the results obtained from applying different decision-making methods to the problem.

Urban storm runoff is considered as a potentially reclaimable and valuable resource in many arid and semiarid areas, in Iran. Urban storm runoff in Shiraz is collected mainly by Khoshk River and transported to the Maharloo Lake without any treatment or reclamation. In this study, storm runoff quality and the possibility for its reclamation from different parts of the city in certain canals and pipes are investigated. The quality of the first flush in three relatively large and small suburban areas with different land uses is studied. For the purposes of this study, three stations were considered: one near the downstream end of the city on Khoshk River with a relatively large watershed, one in the middle of the city where street runoff is the main constituent of the flush, and a third one near the western outskirts of the city with relatively small mainly residential watershed.

Energy plays an increasingly important role in human life. Population growth and shortage of energy warrant optimal utilization of our limited resources. Pumping stations typically run on electric power and economical use of the power is desirable. Serial pumping stations are often required when the pipeline is long or when the required pumping head is too large to be handled by the existing single pumps. In this paper, a new PSO-based model is proposed for optimal operation of serial pumping stations. The proposed model is applied to a real-world situation-the water supply system conveying water from Doroudzan Dam to the city of Shiraz. The results are compared with those of the existing operating policies. Comparisons indicate the high capability of the proposed model.

Modeling vadose zone, particularly the soil water characteristic curve, plays an essential role in unsaturated soil mechanics. This curve depends on such factors as particle size and distribution. A computational procedure acceptable for the assessment of the soil-water characteristic curve is modeling pore size distribution from particle size distribution. In this paper, a model is proposed that considers the variation in local void ratio and evaluates its effect on the soil-water characteristic curve in granular soils with different particle size distributions. Comparison of the results with experimental data shows that the model will predict the soil-water characteristic curve more accurately if a direct relation is established between local void ratio and particle size.

In this research, potassium persulphate and hydrogen peroxide were investigated for their interference in the chemical oxygen demand (COD) test in the presence of reactive blue 19 dye. The chemical oxygen demand (COD) test is widely used for the estimation of the organic carbon content of water and wastewater. The test is prone to disturbance by such inorganic substances as nitrite, chloride, ferrous ion, and sulfide. The interference of chloride and nitrite may be prevented by adding mercuric sulfate and sulphamic acid, respectively. However, the interferences of persulphate and hydrogen peroxide are not mentioned in references. This research was carried out to show how persulphate and hydrogen peroxide interfere with the COD analysis. Results showed that samples containing various concentrations of K2S2O8 and with no organic substances H2O2 had different COD values. It is recommended that the interference of persulphate and hydrogen peroxide should be noticed when running the chemical oxygen demand tests.

Today, coagulants used for water treatment in Iran are predominantly inorganic salts of iron and aluminum while in many countries like Canada, Italy, U.S., China, France and England, and newly in Iran, In Baba Sheikh Ali Water Treatment Plant in Isfahan, a new coagulant named Polyaluminum Chloride (PACl) is used as the alternative coagulant. The present investigation mainly aims to evaluate: (1) the use of Polyaluminum Chloride in place of Ferric Chloride and Alum used as coagulants, (2) the effect of temperature conditions, and (3) the effectiveness of using PACl doubled with starch as a coagulant aid, for turbidity removal of a simulated turbid water with Kaolin. The results showed the trend of floc settlement and higher settling velocity for PACl flocs as well. Coagulation efficiency of PACl proved not to be sensitive to temperature changes, while Ferric Chloride and Alum did. Starch showed to be an effective coagulant aid only at low doses of PACl.