| In the most northeast and northwest of China, surface water is icebound nearly six months in a year. Surface water quality during this period of time is at low temperature, low turbidity and high chroma conditions. With industrial development in recent years, a large number of industrial wastewater is discharged into surface water. Rivers in north have less water supplement in winter, leading to the chroma of water increase. Therefore, the specific water conditions of north China regions are low temperature, low turbidity and high chroma.For years, low temperature, low turbidity and high chroma of water are the hotspots and difficulties in the water treatment works. In recent decades, a wide range of research has been embarked upon treating with this kind of raw water. Currently a series of technologies used by waterworks commonly are flocculation, sedimentation, filtration and disinfection. Flocculation is an important treatment unit in water supply processes, which is essential. Flocculation results will influence the efficiency and water quality of the follow-up handling. Due to the low temperature and low turbidity, dynamic stability and cohesive stability of colloidal particles in water is very strong. Floc is too small and light to be tenacious and sedimentate, and easily pierces the filter material, all of which make water supply quality can not meet these standards in the low-temperature periods.Two aspects are developed to solve the problems in domestic researches, one of which is to intensify the existing water treatment technologies, and the other is to develop new technologies. In the researches of intensifying water treatment technology, some of waterworks used to add clay to raw water, which can promote floc to growth of floc. This method is effective to increase the floc size, but it cause a series of problems, such as the dosage of coagulant increase, the sludge in sedimentation tank increase , filter cycle shortened and residual coagulant increased .etc. Some waterworks have made in-depth study on PAC and polysilicon acid to discuss the best ratio of flocculating agent and coagulant aid. Although most researches to some extent have promoted the development of low temperature, low turbidity and high chroma raw water treatment technology. However, the charge of colloid surface in surface water density is too dense and greater difficulties from stable, water quality is difficult to meet national health standards for drinking water. At present, the new treatment technology to low temperature, low turbidity and high chroma raw water are air flotation technology, sludge recycled technology, micro-flocculation technology and magnetic separation technology. However, these new technologies are not practical for the waterworks have been put into production and most of waterworks commonly strengthen the original water treatment technologies.It is the key to select efficient flocculating agent, coagulant aid and additives in the study on intesified flocculation. Bentonite is widely applied, which can be used in petrochemical, casting, metallurgy, agriculture, textiles and environmental protection, and so on. Jilin is one of the bentonite important producing area and the reserves of which are about 1×105t. Bentonite can be used as additives to increase the raw water turbidity, increase the core of flocculation and adsorb the pollutants causing high chroma.Combined the current technical problems on low temperature, low turbidity and high chroma water treatment, the study is Hunjiang River water in winter as the raw water. Base on modified on the calcium-activated bentonite,the popurse of this experiment is to choose the best flocculating agent, coagulant aid and bentonite for the raw water of Hunjiang River. In-depth studying on mechanism and influencing factors of low temperature, low turbidity water and high chroma water treatment. Finally, explore the best varieties and dosage input from a variety of combinations between activated modified bentonite and coagulants, flocculants in different ratios.The research was a field test in the waterworks of Tonghua Iron and Steel Company. The outlet of waterworks was mainly used in production works of Tonghua Iron and Steel Company. For this, it is necessary to verify turbidity and chroma. It requires that the turbidity is under 5NTU and the chroma is less than 60 degrees.The work included two tests : the activation of modified bentonite and coagulation tests.1) Activation of modified bentonite test. Analysed the various methods of operation to modify bentonite, as well as economic. The wet method was the best method to modify bentonite. Preparation of sodium bentonite (Na salt modified ) , FeCl3 -bentonite, KMnO4- bentonite and FeCl3 -KMnO4- bentonite.2) Coagulation test was static beaker test. In the test, PAC was used as flocculating agent; polysilicon acid and PAM were used as coagulant aid; Calcium bentonite, sodium bentonite, FeCl3- bentonite, KMnO4- bentonite and FeCl3-KMnO4-bentonite were used as additives. Finally, chose the best variety and ratio of flocculating agent, coagulant aid and additive.Through the static beaker test, there were 4 conclusions :(1) PAM is not fit to be applied to low temperature and low turbidity, high chroma treatment. To achieve the desired effect, the dosage was large, but the water quality is poor. It brings on milky white water and higher treatment costs.(2) Addition of activated carbon was able to improve flocculation effect, also completely removed the water chroma. However, due to the property of activated carbon, it should be mixed with water first and kept whisking to prevent sedimentating. After the formation of floc combined with activated carbon, flocculating agent and coagulant aid, it is difficult to recycle activated carbon, resulting in greater waste. And it will increase the processing cost.(3) The modified bentonite in water treatment showed good results. With the addition of bentonite, the dosage of flocculating agent and coagulant aid is reducing. The floc is uniform and sedsided quickly. The volume of sludge is small and compact, the water is clear, whose turbidity and chroma could both meet the requirements. Adding bentonite will not introduce other substances to affect water quality.(4) KMnO4- bentonite had the best effect in all activated modified bentonite. It could reduce the dosage of flocculating agent and coagulant aid by 50%, without adding the chroma removal substance. Finally, the turbidity and chroma of outlet could achieve the desired effects to ensure the follow-up process in normal operation.
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