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首页> 外文会议>2011 water quality technology conference amp; exposition: An Oasis of Ideas for a Changing Environment. >Trials and Tribulations of Operating a Full-Scale Post-Filter Chlorine Contact Basin In a Large Conventional Treatment Plant
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Trials and Tribulations of Operating a Full-Scale Post-Filter Chlorine Contact Basin In a Large Conventional Treatment Plant

机译：在大型常规处理厂中运行全尺寸滤池后氯接触池的试验和试验

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Delaying the point of initial chlorine application is a proven method of reducingrndisinfection by-product (DBP) formation. One way to do this while still achieving Ctrnrequirements is through the use of a post-filter chlorine contact basin. Building uponrnpilot scale and short-term full-scale studies, the Philadelphia Water Departmentrnconducted a lengthy full-scale trial of post-filter chlorine contact basin operation at itsrnBelmont Water Treatment Plant. Though this operation achieved significant success inrnthe area of DBP reduction, it also presented operational challenges that had not surfacedrnin the previous studies.rnThe Belmont Water Treatment Plant is a conventional treatment facility, producing anrnaverage of 50 MGD. Typically, sodium hypochlorite is dosed for disinfection at the rapidrnmix and post-sedimentation. Ammonia is dosed after filtration to form monochloraminernin the clearwell. Coagulation pH is maintained at 6.5, and pH is raised to 7.2 afterrnfiltration but before clearwell storage. From May through October 2010, the clearwellrnwas converted to a post-filter chlorine contact basin. During this time, rapid mixrnchlorination ceased, making the post-sedimentation dosing location the initial point ofrnchlorination. Ammonia and hydroxide addition were moved from the clearwell influentrnto effluent. This now made the clearwell, maintained at pH 6.5, a free chlorine contactrnbasin.rnAt first, costs associated with the clearwell conversion were minimal and included addingrnsome baffling and additional chemical application points and on-line instrumentation.rnThe benefits of the clearwell conversion were tremendous, as DBP levels decreased byrnmore than 50% within hours. However, within weeks of post-filter chlorine contact basinrnoperation, treatment issues began unfolding. An attached algae mat developed on thernwalls and launders of the sedimentation basins. This was accompanied by significantlyrnincreased filter head loss accumulation rates and high post-backwash filter effluentrnturbidities. Numerous strategies were employed throughout the summer months to battlernthe symptoms, including increased algae sampling, additional application of potassiumrnpermanganate at the raw water basin, partially covering the sedimentation basins,rnperiodically shocking the basins with chlorine and application of cationic polymer priorrnto filtration.rnThe periodic shock alleviated the symptoms, but they returned soon after the shock wasrnterminated. None of the other strategies, alone or in combination with others, was able tornsolve the problems. In addition, the plant was plagued by a summer of drought-likernconditions and record-high temperatures. By late August, a combination of cationicrnpolymer at the rapid mix along with partial basin coverage was found to be effective.rnThe polymer continued to be effective into September after the covers were removed.rnAn additional trial was planned for the spring and summer of 2011, to fine-tune thernoperational strategies that seemed to work best. The trial proved more costly thanrnoriginally anticipated, due to additional labor hours, chemical costs and the purchase ofrnmaterials to cover four large basins. Still, the ability to leverage existing infrastructure tornbring about substantial DBP reduction far outweighed the costs.
机译：延迟开始使用氯气的时间是减少消毒副产物（DBP）形成的一种行之有效的方法。在仍满足Ctrn要求的同时做到这一点的一种方法是使用后过滤氯接触池。费城水务部门根据试点规模和短期全面研究，在其贝尔蒙特水处理厂进行了一项长期的全面后试氯接触池操作试验。尽管该操作在减少DBP方面取得了巨大的成功，但它也提出了以前的研究中尚未浮出水面的操作挑战。贝尔蒙特水处理厂是一种常规处理设备，平均损失为50 MGD。通常，在快速混合和沉淀后计量加入次氯酸钠进行消毒。过滤后注入氨，在透明井中形成一氯胺。混凝后的pH值保持在6.5，过滤后但在澄清池中保存之前，pH值升至7.2。从2010年5月到2010年10月，该clearwellrn被转换为过滤后的氯接触池。在此期间，快速混合氯化停止了，使沉淀后的加药位置成为氯化的起始点。氨和氢氧化物的添加从透明井进水转移到出水。现在，这使透明池保持在6.5的pH值，成为游离氯接触池。首先，与透明池转化相关的成本极低，包括增加了一些折衷费力，额外的化学应用点和在线仪器.rn透明池转化的好处是巨大的，因为DBP水平在数小时内下降了50％以上。但是，在滤池后氯接触池运行几周后，处理问题开始显现。附着的藻类垫层沉积在沉积盆地的围墙和洗钱池上。这伴随着过滤头损失累积率的显着提高和反洗后过滤器出水浊度的升高。整个夏季，采取了多种策略来应对症状，包括藻类采样增加，在原水盆地中额外添加高锰酸钾，部分覆盖沉淀池，周期性地用氯冲击盆地以及在过滤之前应用阳离子聚合物。减轻了症状，但休克终止后不久又恢复了症状。其他任何策略，单独或与其他策略结合都无法解决问题。此外，该工厂还受到夏季干旱和高温的困扰。到8月下旬，发现快速混合的阳离子型聚合物与部分盆地覆盖的组合是有效的。rn除去覆盖物后，该聚合物继续有效到9月。rn计划在2011年春季和夏季进行另一项试验，调整似乎最有效的战术策略。由于增加了人工时间，化学费用以及购买了覆盖四个大盆地的材料，该试验的成本比原先的预期高。但是，利用现有基础架构带来的麻烦，即大幅降低了DBP，远远超过了成本。

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