جستجوی مقالات مرتبط با کلیدواژه « Coagulant » در نشریات گروه « محیط زیست »

Coagulation is a process that increases the tendency of small particles in an aqueous suspension to attach to one another and to surfaces such as the media in a filter bed and is applied through mixing coagulants such as aluminum sulfate (alum), ferric chloride and polyaluminum chloride with raw water. Sludge containing coagulant is formed after coagulation and through sedimentation of natural turbidity. Presence of high amounts of coagulant in waterworks sludge, increases environmental risks and disposal costs. Coagulants in sludge have high economic value. Therefore, if these coagulants recover, not only sludge disposal risks but also expenses related to supply of fresh coagulant in water or wastewater treatment plant may decrease. In this paper, researches conducted by acid digestion method for coagulant recovery from waterworks sludge are investigated. Amounts of coagulant recovery, advantages and disadvantages and economic aspects of this method are studied. Results of the investigation showed that using sulfuric acid is the best option for conducting acid digestion process because it is cheap and available. Moreover, if the purpose of recovering process is to achieve a recovered coagulant with a similar quality to the commercial ones, acid digestion method will not satisfy related standards.

Water treatment, according to its substantial role in life and also environmental topics, has a great importance. generally speaking, different methods are utilized in water and wastewater treatment such as: sedimentation, filtration and biologic treatment methods. One of the most important methods applied in water and wastewater treatment is coagulation of suspended solid contents of water using coagulants. Coagulants are divided into non-organic (mineral). synthetic organic and non-synthetic organic groups. In this research, efficiency of non-organic (mineral) coagulants including Ferric chloror, Aluminum phosphate, Poly Aluminum chloride & Polly Ferric Sulphate, in coagulation – flocculation process was studied and compared using a Jar test system. It should be mentioned that for the first time in Iran, Polly Ferric Sulphate was tested during research. According to reported results, this coagulation, compared with other coagulants, indicates better performance in conception, heavier flock’s production higher sedimentation velocity, turbidity removal efficiency, organic carbon removal percent and its good performance in a wider range of temperature and pH. Moreover, because of Ferric base, it does not face with common problems of Aluminum based materials.

Pulp and paper mills consider as a major wastewater producer industries in order to cellulosic pollution and also consuming high amount of water during the process.The wastewater treatment process is complicated because these kinds of effluents contain suspended & colloidal impurities and color & odor; so using chemical coagulants via the Jar test can be an appropriate alternative to remove the contaminants. In this research, different concentrations of Alum, PAC and FeCl3 coagulants were tested to reduce the contamination load of the effluent from three important major parts of fiber wastewater producers; that, according to the results FeCl3 was reported as the best chemical coagulants which removed 61%, 74/05 % and 58% of the COD from the three mentioned parts effluent. Therefore, chemical treatment by using of an appropriate coagulant with the optimum concentration can perform an important role in reducing the effluent contamination load.

Aluminum anodizing plants produce a significant volume of sludge in the final step of wastewater treatment. If this sludge is not disposed by the common methods, it produces several environmental problems, which is taken into account as an imposed cost. The object of this study is economical evaluation of aluminum anodizing plants sludge reusing, to prevent releasing it in the environment and reducing water and soil pollutions. Therefore it causes environmental conservation in one hand and a suitable economical saving can be achieved for these plants in the other hand. For this purpose, data gathering about aluminum anodizing process, the related wastewater treatment units, and various uses of the sludge was performed. It is found that if anodizing sludge uses as raw material in fire- brick preparation, annually 780 million Rials benefit can be achieved by this plant. Furthermore, if anodizing sludge uses as coagulant in municipal wastewater treatment, annually 820 million Rials saving can be obtained by municipal wastewater treatment plants.