水看世界 它们悄无声息地潜伏着——《警惕供水输配系统中残留的锰》

原文链接：

https://awwa.onlinelibrary.wiley.com/doi/epdf/10.1002/opfl.1633

原文作者：

ANDREW S. HILL AND FRANCE LEMIEUX

原文出处：J Opflow

翻译：阮辰旼

Beware of Legacy Manganese Issues in Distribution Systems

警惕供水输配系统中残留的锰

Managing manganese (Mn) levels in drinking water is an important aspect of delivering high-quality water to customers. However, the need to consider and deal with Mn doesn’t simply end at the treatment plant. Significant legacy issues involving Mn accumulation can occur within the distribution system, even in systems that treat for Mn or have low levels of Mn in their water sources. Notably, the current secondary maximum contaminant level of 0.05 mg/L for Mn doesn’t safeguard against its accumulation in the distribution system. Water utilities should recognize the impact of Mn accumulation and release on water quality and implement source-to-tap strategies to limit Mn in their distribution systems.

管理饮用水中的锰（Mn）含量水平是向用户提供高品质饮用水的一个重要方面。然而，考虑并对锰进行处理的需求并不只是到水厂为止。即便对于原水中或者水厂出厂水中锰含量较低的供水系统而言，会导致锰含量上升的重要成因都可能发生在输配系统内。值得注意的是，按照目前水厂二级处理最大污染物浓度限值的规定，锰应小于0.05毫克/升，而且这个限值并不包括锰在输配系统中的累积。因此自来水公司应认识到锰的累积和释放对水质潜在的影响，并实施从源头到龙头的策略来限制输配系统中的锰。

Finished water entering the distribution system is typically clear in appearance, even when Mn is present. Colored-water episodes—particularly water that appears brown, black, or gray—usually signify issues with legacy Mn accumulation and release within the distribution system. “Legacy Mn” represents Mn previously loaded into the distribution system that ended up as deposits on pipe walls, in storage tanks, and in premise plumbing. Under certain conditions, legacy Mn can be remobilized (released) back into the bulk water and result in elevated Mn levels that reach customer taps. As illustrated conceptually in Figure 1, legacy Mn releases can take a variety of forms and can be minor or severe, localized or widespread, short-lived or protracted.

进入输配系统的水厂出厂水通常是透明的，即使存在锰也是如此。发生有色水事件——特别是出现棕色、黑色或灰色的水，通常标志着输配系统内积累的锰出现了溶解并释放到水中。“残留的锰”的概念，一般是指之前进入输配系统的锰，以沉淀物的形式附着积累在管壁、储罐和管道中。在某些情况下，残留的锰会被重新释放到水中，导致到达用户水龙头的锰含量升高。残留的锰的释放有多种形式，可能是轻微的或严重的，局部的或广泛的，短暂的或长期的。

The effect of legacy Mn on aesthetic water quality is well-known. Although utilities tend to associate Mn release events with colored water and customer complaints, significant Mn releases that impart little or no color are alsopossible. Lacking visual (or taste-andodor) symptoms, these releases usually go undetected and risk customer exposure. With releases capable of causing Mn concentrations at the tap that exceed levels of health concern (e.g., Health Canada’s maximum acceptable concentration of 0.12 mg/L), legacy Mn presents an underappreciated public health risk.

残留的锰对水质感官的影响是众所周知的。尽管公用事业部门倾向于将判定锰的释放事件与有色水的客户投诉联系在一起，但存在大量锰释放却很少或没有颜色的变化也是有可能的。有时候由于缺乏视觉（或味觉和嗅味）的表征，这些释放物通常不会被发现，并事实上已经使用户受到了影响。由于残留的锰对公众健康的风险没有得到重视，事实上释放的锰在自来水中的浓度可能已经超过了健康关注的水平（例如，加拿大卫生部规定的最大可接受浓度为0.12毫克/升）。

Even when stable on pipe surfaces, legacy Mn can cause other issues. For example, it can exert a disinfectant demand, support microbial growth, and affect corrosion in pipes (including service lines and premise plumbing) by interfering with the formation of passivating films.

即使在管道表面的累积保持稳定的状态，残留的锰也会引起其他问题。例如，它会产生消毒方面需求，因为累积物会帮助微生物生长，而且累积物也会通过干扰钝化膜的形成而使管道（包括服役的管道和水暖设施）发生腐蚀。

In addition, legacy Mn can chemically bind other inorganic contaminants and cause them to co-accumulate, especially heavy metal cations such as lead (Pb ²⁺ ), barium (Ba ²⁺ ), and cadmium (Cd ²⁺ ). Although these contaminants usually aren’t detectable at system entry points, legacy Mn oxide (MnO _x ) solids can “scavenge” them in water at submicrogram-per-liter (part-per-billion) levels and concentrate them in deposits at milligram-per-gram (part-per-thousand) levels. Once accumulated, these contaminants can be co-released with Mn or chemically desorbed from MnO _x solids. Either mechanism can cause a simultaneous increase in the concentration of multiple inorganic contaminants, exacerbating risks to customers.

此外，残留的锰可与其他无机污染物发生化学反应，导致它们共同累积，特别是重金属阳离子，如铅（Pb ²⁺ ）、钡（Ba ²⁺ ）和镉（Cd ²⁺ ）。尽管通常这些污染物在输配系统的入口段几乎无法检测到，但残留的氧化锰（MnO _x ）固体可以在水中以亚微克/升（十亿分之一）的水平“清除”它们，并使这些污染物以毫克/克（千分之一）的水平浓缩在沉积物中。一旦累积，这些污染物可以与残留的锰共同释放，或从氧化锰固体中化学解析。无论哪种机制都可能会导致多种无机污染物浓度的同时增加，加大用户的风险。

Notably, MnO _x solids have such a large adsorptive capacity for lead that small releases of particulate Mn—even as low as 0.02 mg/L—can co-release lead above 5 μg/L. This is a source of lead at the tap that isn’t considered with regulatory sampling approaches, such as the Lead and Copper Rule, that capture premise plumbing corrosion effects but not dynamic releases that originate within the distribution system.

值得注意的是，氧化锰固体对铅有很强的吸附能力，以至于颗粒状的锰的少量释放，甚至低至0.02 mg/L，也可以导致铅的共同释放超过5 μg/L，这就是用户水龙头处检测到的铅的来源之一。但这个可能性在传统的水质监管和采样方法中没有考虑到，例如铅铜条例（LCRR），它只考虑到了管道腐蚀带来的影响，但没有考虑到来自输配系统中铅的动态释放。

Figure 1. Manganese Release Degrades Water Quality

图1. 锰的释放使水质恶化

Legacy Mn in distribution systems can be released erratically and carry to customer taps.

输配系统中的残留锰可以不稳定地释放，并影响到用户的龙头水。

Mn accumulates in all distribution systems; it’s just a matter of degree. Inventories of legacy Mn—i.e., the accumulated mass of Mn per unit of pipe wall surface area (typical units of mg/ft ² )—can vary by several orders of magnitude between different systems and spatially within a system, depending on past and current Mn loading rates, proximity to sources, main cleaning practices, and other factors. A recent nationwide investigation of inorganics accumulation in distribution system pipe deposits revealed legacy Mn inventories ranging from <0.1 mg/ft ² to 4,000 mg/ft ² , with a median of 210 mg/ft ² . For a 6-inchdiameter pipe, the median equates to 3.8 pounds of legacy Mn per mile of pipe. Because distribution systems often have hundreds of miles of pipe, systemwide inventories of legacy Mn may be on the order of tons for some systems.

锰在所有的输配系统中都会积累，只是程度不同而已。残留锰的存量，即每单位管壁表面积的锰累积量（典型单位为mg/ft ² ），在不同的供水系统之间，或在同一个供水系统内的不同空间上都可能会有几个数量级的差异，这取决于过去和现在的锰含量的负荷、与锰的源头的接近程度、主要的管道清洗做法和其他因素。最近在全国范围内对输配系统管道沉积物中的无机物积累情况进行了调查，发现残留的锰含量从<0.1 mg/ft ² 到4,000 mg/ft ² 不等，中值为210 mg/ft ² 。对于直径为6英寸的管道，中位数相当于每英里的管道有3.8磅的残留锰。由于输配系统通常有数百英里的管道之长，因此，对于一些供水系统来说，整个系统中的残留锰总量可能是以吨计的。

Accumulation Factors. Accumulation of legacy Mn is affected by the magnitude and duration of Mn loading into the distribution system. Although higher loading rates—in particular, Mn >0.02 mg/L—accelerate its accumulation, even systems that treat for Mn or have low levels in their water sources can develop significant legacy Mn inventories after many years. Notably, severe Mn release events have occurred in systems that have supplied water with Mn <0.01 mg/L for decades (see sidebar, “City Resolves Unexpected Manganese Destabilization Event”). Although Mn accumulation can’t be prevented entirely, minimizing the level of Mn entering a distribution system is critical to reducing its rate of accumulation and achieving stable water quality at the tap.

累积因素 。 残留的锰的累积受到输配系统中锰负荷的大小和时间的影响。尽管较高的负荷率，特别是水中的锰>0.02毫克/升时会加速其积累，但即使是原水或出厂水中锰含量较低的供水系统，多年后也会形成大量的残留锰总量。值得注意的是，一些严重的锰释放事件恰恰发生在几十年来水中锰含量小于0.01毫克/升的供水系统中。尽管锰的累积不能完全防止，但最大限度地减少进入输配系统的锰的对降低其累积速度和实现龙头水的水质稳定至关重要。

Accumulation Mechanisms . Mn can accumulate by various physical, chemi-cal, and biological mechanisms, including deposition of Mn particulates in finished water; oxidation of soluble Mn ²⁺ by chlo-rine residual followed by settling of MnOxprecipitates; adsorption/catalytic oxida-tion of Mn ²⁺ on pipe scales and existing MnO _x deposits; and microbial metabolism of Mn ²⁺ with incorporation in biofilm. As shown in Photos 1a and 1b, legacy Mn deposits typically exist as thin, dark films and soft, sludge-like residues that coat the surfaces of pipe and corrosion scale. Like biofilm, Mn films tend to be cohesive and “sticky” in nature, rendering them resis-tant to removal by flushing.

累积机制 。 锰可以通过各种物理、化学和生物的机制累积，包括出厂水中锰颗粒的沉积；可溶性Mn ²⁺ 被氯碱残留物氧化，然后沉淀为氧化锰沉淀物；Mn ²⁺ 在管垢和现有氧化锰沉积物上的吸附/催化氧化；以及Mn ²⁺ 在生物膜中的微生物代谢作用等。残留的锰的沉积物通常以薄而黑的薄膜和柔软的淤泥状的形式存在，它们覆盖在管道和锈垢的表面。与生物膜一样，锰膜往往具有内聚性和“黏性”，使其难以通过冲洗去除。

Photos 1a and 1b. Legacy manganese forms thin, cohesive films on pipe surfaces

照片1a和1b。残留的锰在管道表面形成薄而粘稠的薄膜

Mn release mechanisms are classified as either hydraulic or chemical, depending on the underlying cause. Understanding the differences between these mecha-nisms is necessary to effectively assess and manage risk. Table 1 summarizes these mechanisms, their typical scope of impact, and examples of system events that may cause release.

锰的释放机制分为水力释放和化学释放两种，取决于其释放的根本原因。了解这些机制之间的差异对于有效评估和管理风险是必要的。表1总结了这些机制，它们的典型影响范围，以及可能导致释放的供水系统污染事件的例子。

Table 1. Mechanisms of Manganese Release

图1 锰释放的机制

Mn release mechanisms are classified as either hydraulic or chemical, depending on the underlying cause.

锰的释放机制分为水力释放和化学释放两种，取决于其释放的根本原因。

Hydraulic Release . Hydraulic release involves resuspension of loosely settled deposits due to flow reversals, flow veloc-ity increases, or pressure transients. These result in the release of particulate Mn and produce turbidity proportional to the concentration of released solids. Hydrau-lic releases occur to varying degrees in all distribution systems but are most problematic in systems that have large inventories of legacy Mn and lack a sys-tematic unidirectional flushing (UDF) or main cleaning program.

水力释放 。 水力释放包括由于水流方向逆转、流速增加或压力瞬变而导致的松散沉淀物的重新悬浮。这些都会导致颗粒锰的释放，并产生与释放的固体浓度成比例的浑浊度。水力释放在所有输配系统中都有不同程度的发生，但在有大量残留的锰存量且缺乏系统性的单向冲洗（UDF）或主管道清洗程序的供水系统中问题最大。

Chemical Release . Chemical release involves the destabilization of legacy deposits due to changes in water chemis-try. All pipe scales, including Mn deposits, seek to be at chemical equilibrium with the bulk water. When the water chemistry changes, the oxidation state and physical properties of legacy Mn can also change and cause its dissolution or detachment from pipe walls as it re-equilibrates to the water. Mn is mobilized in soluble form or mixed soluble and solid forms, leading to the possibility of elevated Mn con-centrations with little or no perceptible color. The risk and severity of chemical release depend on the nature and mag-nitude of the chemistry change. Table 2 lists the water chemistry parameters that legacy Mn is most sensitive to and spe-cific risk factors for destabilization. Note that not all chemistry changes are det-rimental to legacy Mn. For example, as shown in Figure 2, treatment to raise pH and/or alkalinity (or, more specifically, dissolved inorganic carbon) for corrosion control can preserve the chemical stabil-ity of legacy Mn.

化学释放 。 化学释放涉及到由于水的化学性质变化而导致的残留沉积物的不稳定。所有的管垢，包括锰沉积物，都试图与管道中流动的水保持化学平衡。当水的化学性质发生变化时，残留的锰的氧化状态和物理特性也会发生变化，导致其溶解或从管壁上脱落，因为它需要与水重新实现化学平衡。锰以可溶形式或可溶和固体混合的形式被进入水中，导致锰的浓度可能升高，但几乎没有可察觉的颜色变化。化学释放的风险和严重程度取决于化学反应的性质和程度。表2列出了残留锰最敏感的水化学参数和破坏稳定的特殊风险因素。请注意，并非所有的化学变化都对残留锰不利。例如，如图2所示，为控制腐蚀而提高pH值和/或碱度（或更具体地说，溶解的无机碳）的处理可以保持残留锰的化学稳定性。

Figure 2. Manganese Pourbaix Diagram

Mn destabilization risks are significant within the typical chemistry regime of distribution systems.

图2. 锰的布拜图

在输配系统的典型化学体系中，锰的不稳定风险是非常大的。

Table 2. Chemistry Risk Factors for Manganese Release

The risk and severity of chemical release depend on the nature and magnitude of the chemistry change.

表2. 锰释放的化学风险因素

化学释放的风险和严重程度取决于化学反应的性质和规模。

To develop tailored, cost-effective Mn con-trol strategies, utilities need to understand legacy Mn and water chemistry conditions in their distribution system. This can be achieved through a system assessment that includes risk screening; investigative water quality monitoring; and, if possible, pipe deposit sampling.

为了制定有针对性的、具有成本效益的锰控制策略，公用事业部门需要了解其输配系统中残留的锰和水的化学状况。这可以通过系统评估来实现，其中包括风险筛选、调查性水质监测，以及如果可能的话，对管道沉积物进行采样。

Risk Screening . Existing data, records, and institutional knowledge should be used to screen zones of the system on the basis of risk factors for Mn accumulation. This will help identify data gaps and focus investigative water quality monitoring activities. Risk screening should consider past and present Mn loading at system entry points (magnitude and duration by source); pipe types, ages, and maintenance histories; water quality–based customer complaint patterns; and field observations by utility crews.

风险筛选 。 应利用现有的数据、记录和理论储备，根据锰积累的风险因素，对供水系统的各个区域进行风险筛选。这将有助于确定数据上的差异，集中调查开展水质监测活动。风险筛选应考虑输配系统的入口处过去和现在的锰负荷（按来源的大小和持续时间）、管道类型、年龄和维护历史、基于水质的客户投诉情况，以及公用事业工作人员的现场观察。

Water Quality Monitoring .  Mn levels can fluctuate significantly in source waters and within treatment plants and distribution systems. To capture potential variations, utilities should have robust source-to-tap monitoring programs. For each source, Mn levels should be monitored in both the raw water and finished water at the entry point to the distribution system, with sufficient frequency to understand seasonal variations and treatment plant performance. Because Mn releases tend to be sporadic and transient, risk- and event-based water quality monitoring should be used within the distribution system. In particular, distribution system monitoring should be performed under the following conditions:

水质监测 。 锰的含量在原水中、水厂中及输配系统内会有很大的波动。为了捕捉潜在的变化规律，公用事业部门应该有强大的从源头到龙头的监测计划。对于每个水源系统，应在进入输配系统的入口处对原水和出厂水的锰含量进行监测，监测频率应足以满足了解季节性变化和水厂工况的要求。由于锰的释放往往是零星的和瞬时的，因此应在输配系统中采用基于风险和污染事件的水质监测机制。特别是，应在以下条件下对输配系统开展水质监测：

● Introduction of new sources or use of seasonal sources

● 当发现了新污染源或存在季节性污染源时 

● Installation of or change in treatment processes

● 当安装或改变了水厂处理工艺时 

● Treatment process upsets that affect finished water chemistry

● 水厂处理工艺发生问题，影响到出厂水化学性质发生变化时

● Changes in water chemistry (e.g., blending, disinfectant changes)

● 水化学性质发生变化时（如混合、消毒剂的变化）。

● Peak demand periods

● 处于用水需求高峰期时

● In response to customer complaints and colored water events

● 需要对客户投诉的有色水事件进行回应时 

System monitoring should include total and soluble Mn; potential co-occurring metals of concern (e.g., lead, arsenic); water chemistry parameters (per Table 2, plus chlorine residual); and source-tracing parameters (e.g., conductivity).

供水系统的水质监测应包括总锰和可溶性锰；潜在的具有共存关联性的重金属（如铅、砷）；水化学参数（根据表2，加上余氯）；以及来源追踪参数（如电导率）。

Pipe Deposit Sampling .  Utilities are encouraged to collect and analyze pipe deposit samples to obtain definitive information on inventories of legacy Mn and co-occurring contaminants. This can involve dedicated pipe extractions to harvest coupons or, more practically, the collection of opportunistic samples from pipe taps, main replacement projects, and main cleaning activities such as UDF. Specialized techniques are needed to harvest, process, and analyze deposit solids.

管道沉积物取样 。 我们鼓励公用事业单位收集和分析管道沉积物样本，以获得关于残留锰和共存污染物存量的明确信息。这可能涉及到专门的管道提取，或者更实际的是，从管道的末梢、结合管道更换作业和管道清洗作业（如UDF）的机会收集样本。这项工作需要有专门的技术来采集、处理和分析沉积物固体。

Utilities should proactively manage legacy Mn risks in their system through best practices for treatment, system operations, and maintenance. The following objectives provide the framework for an effective Mn control plan in distribution systems:

公用事业单位应通过对水处理、系统运行和维护开展最佳实践，积极主动地管理其供水系统中残留的锰风险。以下目标为输配系统中有效的锰控制计划提供了一个框架。

● Minimize loading of Mn into the distribution system.

● 尽量减少输配系统中锰的负荷。

● Minimize accumulated Mn inventories within the distribution system (since accumulation is the precursor for releases, as shown in Figure 3).

● 尽量减少输配系统内累积的残留锰存量（因为累积是释放的前提，如图3所示）。

● Maintain consistent system chemistry to stabilize cohesive deposits.

● 保持供水系统内化学成分的一致性，以保持粘性沉积物的稳定。

To sustainably minimize inventories, utilities need to address the legacy Mn that already exists due to historical loading as well as additional Mn accumulation that develops over time from ongoing loading. This requires routine main cleaning and effective source treatment.

为了可持续地减少残留锰的存量，公用事业部门需要解决由于历史的锰负荷而已经存在的残留锰，以及随着时间的推移因持续的锰负荷而产生的额外的锰的积累。这需要常规的管道清洗和有效的源头控制。

Main Cleaning . Preventive main cleaning provides numerous water quality benefits, including partial or complete removal of legacy Mn. Several cleaning methods are available, including—from least to most aggressive—UDF, air scouring, ice pigging, and foam swabbing. Conventional flushing shouldn’t be used for cleaning because it risks stirring up legacy contaminants without removing them. However, it can be used to turn over the bulk water to help mitigate arelease event, in which case it should be conducted at low flow rates to avoid disturbing deposits (i.e., <150 gpm for mains that are 6 or 8 inches in diameter).

管道清洗 。 预防性的管道清洗提供了许多对水质改善方面的好处，包括部分或完全去除残留的锰。有几种清洁方法可供选择，包括，根据清洗的积极程度的排序，分为管道清洗作业UDF、空气冲刷、冰浆清洗和泡沫拭子。传统的冲洗方法不应该被用于这种类型的清洗，因为它有可能搅动残留污染物而不能彻底去除它们。然而，传统的冲洗可以用来搅动管道内的水，以帮助缓解污染物的释放事件，在这种情况下，管道内的水应该以低流量进行，以避免再让沉积物受到冲击（即，对于直径为6或8英寸的主管道，<150 gpm）。

UDF is the most commonly used main cleaning method because of its relative simplicity. Although highly effective at removing loose deposits, UDF applied at a velocity of 6 ft/sec removes only a small fraction of legacy Mn—typically ≤10% by mass—because of the cohesive nature of Mn films. Consequently, UDF by itself is usually inadequate to prevent major chemical releases, particularly when source or treatment changes are involved. More aggressive main cleaning practices (e.g., foam swabbing) are needed to effectively remove Mn films and minimize chemical release risk.

UDF是最常用的主要清洗方法，因为它相对简单。尽管在清除松散的沉积物方面非常有效，但由于锰膜的内聚性，以6英尺/秒的速度使用UDF方法只能清除一小部分遗留的锰——通常≤10%的质量。因此，UDF本身通常不足以应对重大的化学污染物释放，特别是在涉及源头或水厂工艺改变时。需要更积极的主要清洁做法（如泡沫拭子），以有效地去除锰膜并将化学污染物的释放风险降至最低。

Despite its limitations, routine UDF is still a recommended maintenance practice to reduce the rate of Mn accumulation, to prevent hydraulic releases (by removing the hydraulically mobile Mn), and for other water quality purposes. Systems that have significant Mn accumulation and a high risk of chemical release should also consider foam swabbing or ice pigging.

尽管有局限性，但常规UDF仍是一种推荐的维护做法，因为其可以减缓锰的积累速度，防止水力冲击导致的残留锰释放（通过去除随水流移动的锰），并可以改善其他水质指标。有大量锰积累存量和化学释放高风险的供水系统，也应考虑泡沫拭子或冰浆清洗。

Source Treatment . The adage “an ounce of prevention is worth a pound of cure” applies to Mn control. It’s much better (and less costly on a life-cycle basis) to proactively treat and remove Mn at the source than to allow it to deposit over miles of pipe and deal with it as a legacy issue. Treatment to minimize Mn loading reduces its rate of accumulation in the distribution system and, by extension, the frequency of necessary main cleaning. Treatment should be designed and operated to continuously remove Mn to the lowest level practical and to at least <0.02 mg/L. The previous article in this series (“Evaluate and Optimize Manganese Treatment,” published in Opflow’s December 2021 issue) discussed Mn treatment approaches that can reliably meet this limit.

源头处理 。 有一句谚语“一盎司的预防胜过一磅的治疗”很适用于对锰的控制。从源头上积极处理和清除锰，比让它沉积在数英里长的管道上并作为一个残留问题来处理要好得多（从全生命周期看，成本也更低）。为最大限度地减少锰的负荷而进行的处理，可以降低锰在输配系统中的积累率，从而减少必要的管道清洗频率。水厂工艺的设计和运行应能持续地将锰去除到实际的最低水平，至少达到<0.02毫克/升。本系列的前一篇文章（《评估和优化锰的处理》，发表在Opflow的2021年12月）讨论了能够可靠地满足这一目标的锰处理方法。

Utilities are discouraged from long-term use of treatment approaches that don’t actually remove Mn from the water because these approaches don’t reduce Mn mass loading or accumulation. This includes the use of polyphosphate solutions to chemically sequester dissolved Mn. Sequestration only temporarily masks colored water problems in the bulk water while simultaneously increasing the risk of releasing legacy Mn and other inorganics as a result of chemical interactions between phosphate and pipe scales. Similarly, the blending of multiple water sources, while potentially helpful in lowering the entry-point Mn concentration, reduces neither its mass loading nor its rate of accumulation in the system. Utilities should also be aware that iron- and some aluminum-based coagulant solutions may contain Mn as an impurity, such that their use can add to Mn loading if the Mn isn’t effectively removed in downstream treatment processes.

我们不鼓励公用事业单位长期应用实际上并不能从水中去除锰的工艺方法，因为这些方法不能减少锰的质量负荷或积累，这包括使用聚磷酸盐溶液对溶解的锰进行化学封存。封存只是暂时掩盖了水有异色的问题，同时由于磷酸盐和管垢之间的化学作用，增加了日后残留锰和其他无机物释放的风险。同样，将多种水源进行混合，虽然可能有助于降低进入输配系统处的锰浓度，但既不能减少其质量负荷，也不能降低其在系统中的积累速度。公用事业部门还应该意识到，铁盐和一些铝盐混凝剂溶液可能含有作为杂质的锰，如果在整个水厂工艺中不能有效地去除锰，那么使用这些混凝剂可能会增加锰负荷。

Chemistry Stabilization . Chemical release risk can be reduced by maintaining consistent water chemistry in the distribution system, with emphasis on the parameters in Table 2. This is critical in zones with significant Mn accumulation that can’t be removed with UDF and for which aggressive main cleaning isn’t feasible. Because water chemistry is affected by several factors, utilities should assess spatial and temporal conditions in their system through water quality monitoring and hydraulic modeling.

化学稳定化 。通过保持输配系统中稳定的化学成分，重点是表2中的参数，可以减少化学物质释放的风险。这对有大量锰积累的区域至关重要，这些锰不能用UDF清洗方法去除，而且可能更积极的管道清洗方法也不可行。由于水的化学性质受多种因素的影响，公用事业单位应通过水质监测和水力模型评估其供水系统的空间和时间条件。

Utilities that use multiple sources with dissimilar chemistries face unique challenges because dynamic blending and seasonal operations can cause large chemistry shifts in the distribution system. To address this, treatment might be used to match the finished water chemistries of different sources, although simultaneous compliance needs and/or practical constraints may limit this approach. Alternately, it may be possible to stabilize system chemistry through operational approaches. For example, storage tanks can be operated to receive and mix water from dissimilar sources to promote consistent blends. Conversely, it may be possible to isolate dissimilar sources by restricting their use to separate zones. A potential drawback to each of these operational approaches is reduced supply flexibility.

使用具有不同化学性质的多个水源的公用事业单位面临着独特的挑战，因为不同水源的动态混合和季节性切换会导致输配系统中水的化学性质发生巨大波动。为了解决这个问题，针对不同水源的水厂出厂水化学性质，应该要匹配不同的处理工艺，尽管希望不同水源的工艺同时可以满足这个要求也存在局限。另外，也可以通过一些运行中的操作来稳定供水系统的化学性质。例如，可以通过操作储水池来接收和混合来自不同水源的水，以实现相对稳定的混合结果。反之，也可以通过限制不同水源在不同区域的使用来将不同的水源在具体应用中分开。但这些操作方法都有一个潜在的缺点就是牺牲了供水系统的灵活性。

Planned system changes that pose a high risk of chemical release (e.g., integrating a new source) should be evaluated at the pilot scale beforehand. Pipe loop rigs with harvested native pipes can be used to simulate the anticipated new chemistry regime, assess pipe scale re-equilibration response, and determine appropriate measures for preparing the system.

应当提前在中试规模上对计划中的供水系统变化进行评估，因为这些变化可能具有较高的化学污染物释放风险（如整合一个新的水源）。将截取下来的供水系统中的管道包含在内的换装的试验管网平台可用来模拟预期的水的新化学性质体系，评估管道重新达到化学平衡反应的情况，并为供水系统确定需要准备的适当的措施。

Distribution systems act as accumulation “sinks” for Mn and other inorganic contaminants that are scavenged by Mn solids. Legacy Mn is reactive and mobile with changes in system chemistry and hydraulics, contributing to degraded water quality at customer taps. Even if stable under current conditions, legacy Mn can be a “ticking time bomb” that manifests as a major upset when source, treatment, or pipeline changes are made. Utilities should assess the occurrence and behavior of legacy Mn in their distribution system and develop a proactive Mn control plan to manage risks.

输配系统作为锰和其他无机污染物的积累“集散地”，也会随着颗粒形态的锰的被清除而清除。残留的锰具有反应性，并随着供水系统的化学性质变化和水力冲击的影响而转移，导致用户龙头水的水质恶化。即使在当前条件下可能是稳定的，但残留的锰也可能是一个“定时炸弹”，当水源、水厂工艺或输配管道发生变化时，就可能会造成重大的破坏。公用事业单位应评估其输配系统中残留锰是否出现已经是否由所动静，并制定积极的锰控制计划以管理风险。