1、The potential for the recovery and reuse of cooling water Abstract The cooling water is the major part of industrial wateruse , either from the view of demand priority or supply volume. In order to save water, the loading of supply system can be reduced if the cooling water can be recovered and reus
2、ed. For this reason, exploration of the recent operation status of the cooling water system has become essential . This study was initially focused on the current applications and reuse trends of cooling water in oil refineries, chemical industry, steel mills, food industry, electronics works, texti
3、le plants and power stations. According to the statistical analysis, the portable water and groundwater are the primary sources of makeup water for cooling systems. The multiple-chemicals method and makeup treatment are increasingly accepted for the reclamation of cooling water. On the other hand, s
4、idestream treatment and blowdown reuse are not popular . The recovery rate of blowdown is only 26.8%. The fact of higher cost is the major reason to depress the willingness of recovery. Some representative plants had been selected for case study. However, most cooling water systems are only operated
5、 by operators experience according to field investigation. In each case, the water quality indexes were used to evaluate the operational condition of cooling water systems. There was no case plant found to be operated at appropriate cycles of concentration. This paper also presented the bottlenecks
6、of conservation technologies of cooling water. These bottlenecks include increasing the cycles of concentration, the reuse of wastewater, and the blowdown treatment for reuse. This paper also demonstrates that the recovery and reuse of cooling water has great potential and is feasible for the availa
7、ble technologies , but the industries are still unwilling to upgrade because of initial cost Finally, some approaches associated with technology, economics, environment and policy are proposed to be a reference for the industries and the government authorities. 1999 Elsevier Science B.V. All rights
8、reserved. Keywords: Cooling water； Recovery and reuse； Taiwan； Makeup； Blowdown 1. Introduction The demand of water resource has apparently increased because of the highly economical growth, rapid industrial development and the upgrading of living standard in . The water source is difficult to devel
9、op economically due to land sinking, groundwater pollution and the difficulty of new reservoir construction. Therefore, how to reclaim and reuse the water is an efficient way to solve this problem. Among the industries wastewaters, the cooling water is most valuable for recovery because it has large
10、r volume and is less contaminated. On the other hand,some industries reuse the properly treated process wastewater or domestic sewage for cooling. Although the multiple chemicals dosage method is a mature technologyto increase the recycling amount, the potential must be evaluated for the reuse and r
11、ecovery of cooling water when enhancing the execution of reusing cooling waterfurther. This study is interested in perceiving the matters concerned with cooling water quality, treatment technology for reclamation and the feasibility of recovery and reuse. 2. The characteristic and operational proble
12、ms of cooling water system The cooling water systems were divided into once through, open recirculating and closed recirculating systems. The operating problems of cooling water system are combined with corrosion, scale, fouling and slime . Corrosion is induced by the electrochemical reaction and in
13、duces the weight loss of metal. The scale is formedunder metal salts supersaturation, e.g. calcium, magnesium, and formed sediments on the metal surface. Fouling is caused by the corrosion products or the suspended matter that is attached on the metal surface. Slime is caused by the growth of microo
14、rganism which also combined microorganical fouling and corrosion, etc. The operational problems described as above are normally concerned with the characteristic of the cooling water system. Therefore, the water quality needs to be carefully considered when reusing the cooling water. Table 1 display
15、ed the relationship between the more important water constituents and the operational problems of the cooling water system. If a cooling water system is operated under the characteristics of neutral pH, lower temperature, higher velocity, lower concentration of dissolved salts and nutrition matter,
16、the situation of operational problems can be reduced. 2.1Changes over time in different locations between ammonia Fig.2 Variation of NH3-N in leachate with the lapsed time and the different areas From the figure, the overall trend curve can be seen from the more recent sampling point pollution sourc
17、es, pollutants and, generally higher, close to the sand box at the bottom and away from sources of ammonia concentration at the latest sampling point, reflecting the most insensitive. As the leachate into the passage of time, changes in pollutant concentration with distance curve is also gradually m
18、ove over, along with changes in the amount of leachate into the concentration of the sampling points followed by corresponding changes. At the level of ammonia migration rate decreased gradually along the flow direction, the attenuation rates were increased. Ammonia used to migrate to G2 point of ti
19、me of about 12d, used to reach the point of time is about K2 30d, migration rate is determined by 4cm / d down to 3.2cm / d； decay rates were higher: C2, G2, K2 three largest ammonia concentration ratio of C2: G2: K2 = 732:477:86. In the vertical, the nitrogen transfer rate along the flow direction
20、followed by increased migration of ammonia from C3 to C1 point point of time used for the 15d so, G3 G2 G1 in the first 15d, three were detected ammonia. Along the flow direction and reduce the concentration of ammonia under different a 水平方向各点氨氮浓度变化-10001002003004005006007008000 10 20 30 40 50 60时间/ d浓度/(mg.L-1)C2E2G2I2K2b 垂直方向各点氨氮浓度变化-10001002003004005006007008000 10 20 30 40 50 60时间/ d浓度/(mg.L-1)C3C2C1G3G2G1
