WATER AND WASTEWATER
Year:2007 | Volume:18 | Issue:2 (62)|Papers Count:10

Over the course of producing and marketing goods and services, it appears that industry faces a new challenge in which information and science form the basis for any organizational movement. In this regard, the competitive preference of the organization concentrates on customer and value creation in the organization. Value engineering recognizes product/service functions and produces those with the maximum value at the lowest cost without the loss of production or service quality and safety. In this paper, using value engineering based on the international job plan of the SAVE (Society of American Value Engineering), various alternatives are proposed to improve upon the performance of Customer Services of Water and Sewage Co. The results indicate possible savings of about 714 Million Rials for the water authority in the city of Sari and 4860 Million Rials across Mazandaran Province.

Increasing population and socioeconomic development have led to increased urban water demand. Residential use forms the principal portion of urban water consumption. One of the most effective residential water conservation measures is using low-flow fixtures and devices designed for this purpose. In this paper, conservation results of using low-flow fixtures including low-flow showerheads and faucet aerators are evaluated in the city of Kashan. For this purpose, two groups of 40 households were randomly selected as experimental and control groups. The fixtures were installed in the houses of the experimental group and water consumption was measured over one month. Results indicate that retrofitting with these fixtures reduces residential water consumption by about 22 percent. Projections of Kashan’s future water demand and supply indicate that using these fixtures by Kashan residents can delay the need for new water supply projects by up to 6 years. Cost-benefit ratio of this conservation measure for Kashan is estimated to be 5.8 to 1. Finally, user satisfaction of retrofitting with these fixtures is evaluated.

Oil and heavy metals pollution was investigated in the Persian Gulf coastal waters near Booshehr Province. The most polluted areas were found to be Imam Hassan and Assalluyeh, showing PAH (Polycyclic Aromatic Hydrocarbons) levels of 9.83 and 1.29 ppm, respectively. PAHs such as naphthalene and phenanthrene (pollutants with petroleum, coke, and industrial origins) find their way into the environment. Soil samples were taken from these polluted areas to isolate species of bacteria with the highest biodegradation capability. Eight species were recognized, most of which belonged to the pseudomonas, gram negative, and catalase positive organisms. The species were tested for their biological removal capability and the best four were used in an RBCp bioreactor to study their pollutant removal capability. Under steady conditions, a COD removal of 73% and a PAHs removal of 66% were recorded. A moving bed bioreactor (MBBR) was also used to investigate TPH biological removal using the same bacteria. The experiments were performed under three acclimatization periods of 48, 36, and 18 hours within a COD range of 800-2000 mg/l. The results showed that maximum COD and TOC removal efficiencies of 81% and 79%, respectively, can be achieved in mixed growths of the isolated bacteria.

Numerous advantages have been reported on PAC (poly aluminum chloride) used as a coagulant over other coagulants such as alum and ferric chloride used in conventional water treatment process with medium and high turbidity levels. These include lower amounts of PACL required specially in removing turbidity, larger floc grain formation, reduced floc sedimentation time, lower sludge production, and relaxation of the need for pH adjustment by lime, among others. The present study aims to evaluate the effects of different coagulants such as ferric chloride and PACL on direct filtration and to identify the most effective material based on both turbidity and particle removal efficiencies. A perfectly experimental pilot system, including raw water preparation, coagulation, flocculation, distribution measurement, and filtration units, was designed and used. Raw water turbidity level in the experimental pilot was below 10 NTU. The effects of various parameters such as coagulant type, filtration rate, and coagulant dosage on the performance of the filter were investigated. The results obtained from several filtration cycles under different conditions indicated that average effluent turbidity level, effluent particle numbers, effluent turbidity variation graph, and effluent particle graph were lower throughout the filtration cycle when PACL was used compared to when ferric chloride was used as the coagulant. Increasing filtration rate led to increased turbidity and particle number. Addition of 2 mg/l of PACL (poor coagulation and flocculation scenario) was compared with addition of 5 mg/l of ferric chloride (strong coagulation and flocculation scenario). The results indicated that higher average values of turbidity removal but lower turbidity and particle removal efficiencies obtained in the case of the poor coagulation and flocculation scenario.

The performance of electrocoagulation, with aluminum sacrificial anode, has been investigated. for removal of Cr (VI)), Several working parameters, such as pollutant concentration, pH, electrical potential, COD, turbidity, and reaction time were studied in an attempt to achieve higher removal efficiency levels. Solutions of varying chromium concentrations (5-50-500 ppm) were prepared. To follow the progress of the treatment, samples of 25ml were taken at 20 min intervals for up to 1 h and then filtered (0.45 μ) to eliminate sludge formed during electrolysis. The pH of the initial solution was also varied to study its effects on chromium removal efficiency. Results obtained with synthetic wastewater revealed that the most effective chromium removal efficiency could be achieved when a constant pH level of 3 was maintained. In addition, increased electrical potential, within the range of 20-40V, enhanced treatment rate without affecting the charge loading, but required reduced metal ion concentrations to below admissible standard levels. The process was successfully applied to the treatment of an electroplating wastewater where an effective reduction of Cr (VI) concentration below standard limits was obtained just after 20-60 min. The method was found to be highly efficient and relatively fast compared to conventional techniques. Thus, it may be concluded that electrocoagulation process has the potential to be utilized for the cost-effective removal of heavy metals from water and wastewater.

Despite extensive research carried out on sludge bulking, it is still a common problem world-wide and a comprehensive solution is yet to be developed. In this research, the effect of three-stage anoxic selector on controlling activated sludge bulking is investigated in laboratory sludge systems. These experiments were carried out on two pilot plants; a three-stage anoxic selector preceding a complete mix system (experimental unit) and a complete mix system (control unit). Results from this study indicate that in selector zones with F/M ratios high enough to allow for rapid substrate uptake to occur predominately by floc forming microorganisms, the sludge settleability is influenced by the mode of substrate removal in the selector and by floc loading along the following lines. The substrate storage mechanism predominates in substrate removal for lower floc loadings, leading to improved sludge settleability, while for higher floc loadings the high rate metabolic mechanism predominates for substrate removal, leading to impoverished sludge settleability.

Viscous bulking is a typical problem arising in activated sludge facilities treating effluent from soft drink plants. The drawbacks associated with this phenomenon include increased effluent organic loading and undesirable sludge settlement. In order to investigate this phenomenon, a soft drink factory was selected as a pilot plant for a case study (where metal tanks were used as a biological selector, an aeration basin, and a clarifier). The study shows that the major causes of viscous bulking are high organic loading and undesirable ratio of monovalent to divalent cations. In the biological selector (with a retention time of 20 hours), while the organic load in the influent to the aeration basin decreased by about 50%, with an impact on reduced viscous bulking, pH value decreased from 12 to 6.5 due to fatty acids production. Adjustment of Na/Ca ratio improved bacterial surface hydrophobicity and prevented degradation of biological flocs. This resulted in improved sludge settleability. Application of this method improved sludge settling, made flocs stronger, and reduced effluent organic load (COD) to less than 150 mg/l, indicating stability of the system.

One aspect of sewage sludge application as an organic fertilizer on agricultural farms is environmental pollution concerns such as heavy metals uptake by plants. The aim of this study was to investigate the influence of amended sewage sludge application on yield and heavy metal uptake of Barley. This study was carried out over a period of barley growth with two treatments of sewage sludge (50 and 100 ton/ha) and control treatment with four replicates arranged in a randomized complete block design. Plant samples were taken at three intervals (50, 90, and 180 days after sowing). The samples were prepared for measuring nutrients and heavy metals in stem, leaf, straw, and grain. Results of plant analysis showed that application of sewage sludge increased nitrogen, phosphorous, potassium and cadmium in vegetative parts compared to control. Grain analysis showed that application of sewage sludge significantly increased nitrogen, phosphorous, potassium, iron, and zinc. Grass yield significantly increased in the plot treated with 100 ton/ha sewage sludge. Grain yield in the two treatments significantly increased. The results revealed that the sewage sludge increased heavy metals uptake by plants but still below standard levels. It is, therefore, necessary to use the quantities of the elements introduced into soil and absorbed by plants in order to determine the toxicity level for each metal taking into account factors such as plant and soil types as well as environmental conditions. This information can then be used to determine sludge application quantities in each case. Meanwhile, sludge application may only be recommended for irrigated crops receiving adequate irrigation water due to its salinity. Moreover, it cannot be recommended for irrigated crops directly consumed by man.

In spite of different water resources available at many locations, adequate supplies of fresh water are rare for human demands due to various sources of pollution. Water pollutants can be classified as 1) suspended pollutants and, 2) dissolved pollutants. Dissolved pollutants consist of acids and heavy metallic ions. Foam fractionation method which is based on differences in surface activity is a new method whereby dissolved solids are adsorbed on the surface of liquid bubbles. Various purposes are served by the separation of metallic ions from water which includes removal of metallic ions from water and extraction of precious metals from wastewater. In this method, water is mixed with a surfactant and fed continuously to a column. The supernatant foam thus formed starts to move along the column neck. Finally the foam breaks up into two fractions of heavy metal ions and pure water each leaving the column through separate outlets. In this study, neck height design and optimization is investigated to achieve the best copper ion removal efficiency. Based on our experiments, it was found that increasing neck height up to a certain height increased the enrichment ratio. Also increasing metal ion concentration for a given neck height improved recovery.