
长距离供水管网中不同水质影响下的中途补氯优化
王诗宇, 林涛
长距离供水管网中不同水质影响下的中途补氯优化
Optimization of Booster Chlorination under Different Water Qualities in the Long-distance Water Distribution System
为探寻更具普适性的长距离供水管网中途补氯方案,分别进行了不同初始氯浓度下的一次投氯和中途补氯的对比试验,比较分析了水质差异较大的两个水厂(WTP1和WTP2)出厂水的余氯衰减规律和两种典型消毒副产物三氯甲烷(CHCl3)和二氯乙腈(DCAN)的生成规律。结果表明,在供水管网总需氯量低于1 mg/L时可采取一次投氯的方式对出厂水进行消毒处理,高于1 mg/L时,建议采用中途补氯的方式消毒;在进行中途补氯时将补氯位置控制在余氯衰减至0.2 mg/L左右时最佳。相较一次投氯,采用中途补氯时两个水厂出厂水余氯衰减时间的延长率分别为9.5%、13.8%、15%(WTP1)和12.5%、16.7%、22.9%(WTP2),中途补氯的情况下CHCl3总生成量比一次投氯减少了12%~25%左右,DCAN减少了8%~18%左右。中途补氯能明显减缓余氯的衰减,有效降低管网中的含碳消毒副产物(C-DBPs)及含氮消毒副产物(N-DBPs)的生成潜能,且当管网中总需氯量越高、水体水质越差时,中途补氯的优势相较于水质好的水体也越明显,但两者消毒副产物总体变化规律相似。在初始投氯与中途补氯配比为1∶1时,余氯在管道中维持的时间最长,管网余氯分布的均匀性最好,且对CHCl3和DCAN生成量的控制效果最优,当总投氯量改变时,该结论仍成立。建议选择1∶1作为中途补氯过程中初始氯浓度与中途补氯的最佳优化配比。
In order to explore a universal long-distance booster chlorination scheme, a series of comparison experiments of one-time chlorination and booster chlorination under different initial chlorine concentrations is carried out, the residual chlorine decay and production of two typical disinfection by-products chloroform (CHCl3) and dichloroacetonitrile (DCAN) are compared and analyzed for the drinking water in two water treatment plants with different water qualities. The results show that when the total chlorine demand of water distribution system(WDS) is less than 1 mg/L, the finished water can be disinfected by a single injection of chlorine; when it is higher than 1 mg/L, booster chlorination is recommended, and the booster chlorination stations should be set in the pipeline network when the residual chlorine decays to about 0.2 mg/L. Compared with one-time chlorine injection, the decay time extension rates of residual chlorine from two water works are 9.5%, 13.8%, 15% (WTP1) and 12.5%, 16.7%,22.9% (WTP2), respectively. In the case of booster chlorination, the total yields of CHCl3 decreases by about 12%~25% and DCAN by about 8%~18%, respectively. Booster chlorination can significantly reduce the attenuation of residual chlorine, effectively reduce the formation potential of carbonaceous disinfection by-products (C-DBPs) and nitrogenous disinfection by-products (N-DBPs) in WDS. Moreover, when the chlorine demand is higher and the water quality is worse, the advantage of Booster chlorination is more obvious than that of water with good water quality, but the overall change of DBPs is similar. When the dosage ratio of initial to booster chlorine is 1∶1, the residual chlorine in the pipeline network remains the longest, and has the best uniformity. In addition, the control effect on the generation of CHCl3 and DCAN is optimal. The conclusion still holds as the total chlorine demand changes. Choosing 1∶1 is recommended as the optimal ratio between the initial and booster chlorine dosage.
供水管网 / 余氯衰减 / 中途补氯 / 消毒副产物 {{custom_keyword}} /
water distribution system / residual chlorine decay / booster chlorination / disinfection by-products {{custom_keyword}} /
表1 WTP1与WTP2原水及出厂水水质数据Tab.1 Raw water and finished water quality data of WTP 1 and WTP 2 |
水厂 | 类型 | 浊度/NTU | pH | 温度/ ℃ | CODMn/ (mg·L-1) | TOC/ (mg·L-1) | 细菌总数/(CFU·mL-1) |
---|---|---|---|---|---|---|---|
WTP1 | 原水 | 19.00 | 7.7 | 25 | 1.63 | 2.9 | 75 |
出厂水 | 0.13 | 7.5 | 25 | 0.79 | 1.7 | 未检出 | |
WTP2 | 原水 | 87.70 | 7.7 | 26 | 4.85 | 5.6 | 850 |
出厂水 | 0.45 | 7.6 | 26 | 1.39 | 2.8 | 9 |
表2 WTP1和WTP2中途补氯试验分析结果Tab.2 Results of booster chlorinaton for WTP1 and WTP2 |
投氯方式 | 总投氯量1.5 mg/L | 总投氯量2 mg/L | 总投氯量3 mg/L | ||||
---|---|---|---|---|---|---|---|
t 0.05/h | 延长率/% | t 0.05/h | 延长率/% | t 0.05/h | 延长率/% | ||
WTP1 | 一次投氯 | 21 | - | 36 | - | 60 | - |
初始与中途余氯配比 | 1∶1 | 23 | 9.5 | 41 | 13.8 | 69 | 15.0 |
1∶2 | 22 | 4.8 | 39 | 8.3 | 66 | 10.0 | |
2∶1 | 22 | 4.8 | 38 | 5.6 | 65 | 8.3 | |
WTP2 | 一次投氯 | 16 | - | 30 | - | 48 | - |
初始与中途余氯配比 | 1∶1 | 18 | 12.5 | 35 | 16.7 | 59 | 22.9 |
1∶2 | 17 | 6.3 | 32 | 6.7 | 54 | 12.5 | |
2∶1 | 17 | 6.3 | 32 | 6.7 | 55 | 14.6 |
图3 不同总投氯量下的一次投氯和3种不同补氯配比时的余氯衰减规律变化Fig.3 Residual chlorine decay of chlorination and three different dosage ratio between initial and booster chlorination under different total chlorine concentrations |
表5 WTP1和WTP2中各组试验余氯浓度的平均值与标准差Tab.5 The average value and standard deviation of the residual chlorine concentration of each group in WTP1 and WTP2 |
水厂 | 总需氯量1.5 mg/L | 总需氯量2.0 mg/L | 总需氯量3.0 mg/L | ||||
---|---|---|---|---|---|---|---|
初始与中途余氯浓度配比 | 平均值/(mg·L-1) | 标准差 | 平均值/(mg·L-1) | 标准差 | 平均值/(mg·L-1) | 标准差 | |
WTP1 | 1∶1 | 0.38 | 0.20 | 0.53 | 0.30 | 0.73 | 0.48 |
1∶2 | 0.39 | 0.28 | 0.56 | 0.36 | 0.76 | 0.56 | |
2∶1 | 0.41 | 0.26 | 0.57 | 0.38 | 0.81 | 0.57 | |
WTP2 | 1∶1 | 0.36 | 0.21 | 0.49 | 0.30 | 0.69 | 0.49 |
1∶2 | 0.38 | 0.28 | 0.51 | 0.39 | 0.74 | 0.61 | |
2∶1 | 0.37 | 0.26 | 0.53 | 0.35 | 0.74 | 0.57 |
图4 不同初始氯浓度下各试验组初始与最终CHCl3生成量Fig.4 The initial and final CHCl3 yields of each group under different initial chlorine concentrations |
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