陪你去看满天星——《运营人员需要了解的深度处理工艺》

原文链接：

https://awwa.onlinelibrary.wiley.com/doi/epdf/10.1002/opfl.1661

原文作者：

Hunter Adams,Steve Ash,Keisuke Ikehata,Mark Southard

原文出处：J Opflow

翻译：阮辰旼

Operators Need to Know Advanced Treatment Processes

运营人员需要了解的深度处理工艺

Although conventional water treatment processes are tried-and-true methods, advanced treatment processes are gaining popularity worldwide. Advanced treatment involves processes that remove contaminants that normally wouldn't be eliminated by conventional means. For more information on conventional treatment, see “Operators Need to Know Conventional Treatment Processes,” which appeared in Opflow’s March 2022 issue. This article provides a basic overview of advanced treatment processes being brought online by many utilities, providing operators with a working knowledge of newer treatment techniques and why they may be implemented by their utilities in the future.

尽管传统的水处理工艺是久经考验的工艺方法，但深度处理工艺在全球范围内越来越受到欢迎。深度处理涉及到去除通常无法通过常规工艺去除的污染物的过程。有关常规处理的更多信息，请参见“运营人员需要了解的常规处理工艺”，该文发表在Opflow期刊的2022年3月刊（第2期）上。本文提供了许多公用事业单位正在上马的深度处理工艺的基本概述，为运营人员提供了较新的处理工艺的工作知识，以及为什么他们所在的公用事业单位在未来可能会上马这些工艺。

Dissolved air flotation (DAF) is a specialized treatment technology that uses microbubbles to float particulates to the surface of a basin or chamber. The process of separating solids from liquids, which is different from typical gravity separation, is a modification of diffused air flotation, a process in which air diffusers on the floor of a water or wastewater treatment basin distribute large air bubbles into the water column to float particles or grease to the surface, introduce oxygen into the water, or remove unwanted dissolved gases from the water.

针对溶解性物质的气浮工艺（DAF）是一种针对性的处理工艺，它利用微气泡将颗粒物漂浮到反应器的表面。这种从液体中分离固体的过程与传统的重力分离不同，它的主要改进是利用扩散空气的浮选作用，在工艺过程中，水或废水处理器内的空气扩散器将气泡分布扩散到水体中，将颗粒或油脂浮到表面，同时将氧气引入水中，或从水中去除不需要的溶解性气体。

In the DAF process, diffusers are replaced by an air–water saturator. Compressed air is forced into a closed vessel of water, and the increased pressure dissolves the air into the water. The air-saturated water is then pumped from the saturator into the bottom of an open basin. At that point, the pressure holding the air in solution is relieved, and the dissolved air comes out of solution, forming billions of microbubbles that float algae and other lightweight solids to the water's surface. A skimmer continuously removes the accumulated material and directs it to a waste channel. The clarified water then exits the chamber and continues through the plant for further treatment (Figure 1).

在气浮工艺（DAF）中，空气-水饱和扩散器作为气体扩散的来源。压缩空气被注入一个封闭的水容器中，增加的压力将空气溶解到水中。然后，含有饱和空气的水被通过扩散器从反应器的底部释放。在扩散器中，溶液里保持着压力的气体被释放，形成数十亿的微气泡，将藻类和其他轻质的固体托浮到水面。有一个除渣器不断地清除表面积累的物质，并将其引导到一个排泥通道。然后，澄清的水从反应器中流出，继续通过水厂的后续工艺进行进一步处理（图1）。

Figure 1 Dissolved Air Flotation (DAF)

表1 气浮

DAF is a process in which gas bubbles are generated so they will attach to solid particles, causing them to rise to the surface rather than settle to the bottom. Here, Microcystis colonies in a clarifier (left) are removed by DAF and skimming (right).

气浮包括一个产生气泡的过程，气泡会附着在固体颗粒上，使它们上升到液体表面而不是沉降到底部。在液体的表面，澄清池中的微囊藻菌落（左）被气浮工艺和除渣器（右）去除。

Surface water treatment plants use DAF to separate algae from raw lake water, but the process has several benefits. First, it removes colloidal organic material, thereby reducing the potential to form disinfection byproducts (DBPs), such as trihalomethanes. Second, it can reduce the potential for cyanotoxin release by removing cyanobacteria before they are destroyed during treatment. Lastly, and most noticeably, it can reduce taste and odor (T&O) compounds commonly associated with algae and cyanobacteria. This is accomplished by removing the algal and cyanobacterial cells instead of destroying them, thereby preventing the widespread release of intracellular compounds as the cells die (see sidebar, “DAF Solves Algal Bloom Issues”).

地表水处理厂可以使用气浮工艺从湖泊原水中分离藻类，该工艺过程有几个好处：首先，它可以去除胶体状的有机物，减少生成消毒副产品（DBPs）的可能性，如三卤甲烷等；其次，它可以在蓝藻被水厂工艺杀灭破坏之前先将其去除掉，从而减少蓝藻毒素释放的可能性；最后也是最显著的是，它可以减少与藻类有关的嗅和味（T&O），而且是通过分离而非通过杀灭破坏藻类细胞来实现的，可以有效防止藻类细胞死亡时细胞内化合物的释放。

Filtration removes remaining suspended solids after clarification. Clarifier effluent enters filters that act as a physical barrier and ideally remove everything except dissolved solids. Conventional filtration using granular media (sand/anthracite) effectively removes particulates down to around 10 μm in diameter. Removing particulates <10 μm requires membrane filtration (Figure 2).

过滤工艺可以去除澄清后剩余的悬浮固体。澄清池的出水进入过滤池，作为物理屏障，最理想的状态是能够去除除溶解性固体以外的一切固体。使用颗粒介质（沙子/无烟煤）的传统过滤工艺能有效去除直径大于10微米的颗粒。而去除直径小于10微米的颗粒则需要膜过滤（图2）。

Figure 2 Membrane Filtration Particulate Removal Size and Operating Pressure Ranges

表2 膜过滤去除颗粒的大小和操作压力范围

A large arsenal of membrane materials and platforms are available to treat most source waters and provide a long service life.

多种膜材料和膜过滤平台可用于处理大多数的原水，并可以保证较长的使用寿命。

In membrane filtration, pressurized water is pumped through membranes, separating the permeate (filtered water) from the concentrate (filtered reject containing concentrated solids). Concentrate disposal must be considered when implementing membrane filtration because of the concentrated salts and other contaminants in the waste stream. Operational costs are also a factor because they increase as membrane pore size decreases due to more energy being required to generate the increased pressures needed for operation. As a result, conventional granular media filters have higher flow rates, and flow rate decreases with membrane filtration as pore size decreases. Large capital investments are required to replace membranes over time as they degrade.

在膜过滤的过程中，通过泵加压的水通过膜，将渗透液（过滤后的水）与浓缩物（含有浓缩固体的过滤废液）分离开。在实施膜过滤时，必须要考虑浓缩物废液如何处理，因为废液中含有浓缩的盐和其他的污染物。运行成本也是一个需要考虑的因素，会随着膜孔径的减小而增加，因为需要更多的能量来产生运行所需的压力。因此，传统的颗粒介质过滤工艺往往拥有更高的流速，但流速会随着膜过滤的孔径的减小而减缓。随着运行时间的持续，随着膜的老化，还需要大量的成本投资来更换膜。

The four general membrane processes that operate by applying pressure to raw water are microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO).

常规的需要通过对原水加压来实现的膜过滤过程包括微滤（MF）、超滤（UF）、纳滤（NF）和反渗透（RO）。

Photo 1

Reverse osmosis (RO) membrane systems, such as the Cypress Water Treatment Plant RO skids shown here in Wichita Falls, Texas, remove essentially all organic and inorganic constituents.

照片1 反渗透（RO）膜系统，如德克萨斯州威奇托福尔斯市的赛普拉斯水处理厂的RO工艺，基本上可以去除所有有机和无机物。

MF and UF .  MF uses membranes with 0.1-μm pores, which can remove protozoans and bacteria. UF uses membranes with 0.01-μm pores, which can remove viruses. Both MF and UF remove suspended particles, whereas NF and RO remove dissolved constituents. MF and UF can be used postclarification or in place of clarification if source water is low in suspended solids.

微滤和超滤 。  微滤使用具有0.1微米孔径的膜，可以去除原生动物和细菌。超滤使用孔径为0.01微米的膜，可以去除病毒。微滤和超滤都能去除悬浮颗粒，而纳滤和反渗透可以去除溶解性的成分。如果原水中的悬浮物含量低，微滤和超滤可以在澄清工艺后使用，或直接代替澄清工艺。

Coagulants may be used in prefiltration to adsorb organics that settle out in clarifiers and are then separated out by MF/UF membranes. As with conventional filtration, MF/UF systems must be backwashed regularly, or when performance declines, with back-pressured water and/or air. Also, they must be periodically soaked in a cleaning solution, depending on membrane material and application. A clean-in-place procedure must be used periodically in accordance with manufacturer recommendations to remove excess buildup of particulates and to disinfect the membranes.

混凝剂可用于过滤该工艺的前序工艺，使有机物吸附在澄清池中沉淀的固体上，及后续通过微滤或超滤膜进行分离。与传统过滤一样，微滤和超滤系统必须定期进行反冲洗，或在过滤性能明显下降时，用反向的压力水和/或空气进行反冲洗。此外，必须定期将膜浸泡于清洁溶液中，这取决于膜材料和具体的应用场景。必须根据膜制造商的建议，定期开展原位的清洗程序，去除多余的颗粒物堆积，并对膜进行消毒。

NF .  NF uses membranes with 0.001-μm pores, which can remove dissolved ions and natural and synthetic organics. NF is often used to remove color and hardness (e.g., calcium and magnesium) from groundwater. Rejection (removal) of monovalent ions (e.g., sodium and chloride) is limited depending on the types of NF membrane used. NF membranes and equipment are similar to those of RO. Although the RO process requires higher pressure to overcome full osmotic pressure due to total dissolved solids (TDS), the NF process requires much less pressure because of the partial rejection of TDS. Permeate recovery is usually higher (~90%) than in RO. Smaller ions and molecules, such as dissolved gases (e.g., hydrogen sulfide), can't be removed by NF. Therefore, air stripping is often required as a posttreatment process. Additional posttreatment options include calcite/lime addition or blending with bypass water to reduce corrosivity. The concentrate stream (1, 2) needs to be properly disposed of via surface water discharge, deep well injection, or a sewer.

纳滤 。 纳滤使用具有0.001微米孔隙的膜，可以去除溶解性的离子以及天然或合成的有机物。纳滤经常被用来去除地下水的色度和硬度（如钙和镁）。对单价离子（如钠和氯）的去除是有限的，但这取决于所使用的纳滤膜的类型。纳滤膜工艺配套的设备与反渗透相似。反渗透过程需要更高的压力，以克服总溶解性固体（TDS）产生的全部渗透压，但因为可以允许通过TDS中的部分离子，纳滤膜工艺需要的压力要小得多。纳滤膜工艺渗透液的回收率通常比反渗透的高（约90%）。由于较小的离子和分子，如溶解性的气体（如硫化氢），不能被纳滤膜去除，因此，通常需要将气提作为后处理过程。纳滤膜配套的额外的后处理选择包括添加钙/石灰或与其他生产线的水混合以减少对管网的腐蚀性。浓缩液需要通过地表排放、深井注入或排入排水系统以进行适当处理。

Photo 2

Samples show concentrate from a colored water NF train (left) and a brackish groundwater RO train (right) in Florida.

照片2 如图的样品是来自佛罗里达州的经过纳滤膜处理的有色水浓缩废液（左）和经过反渗透处理的地下苦咸水浓缩废液。

RO .  RO uses membranes with <0.001-μm pores, which can remove almost all dissolved material (e.g., ions, metals, etc.). RO is commonly used to remove TDS from source waters. It's an effective choice when desalination is needed, but it produces a concentrated reject (Figure 3). Also, RO can remove other contaminants, such as sulfates, nitrates, pesticides, heavy metals, and radionuclides. Due to an RO membrane's small pore size, some type of clarification/filtration process is required before RO, unless the source water is low in suspended solids.

反渗透 。  反渗透使用孔径小于0.001微米的膜，可以去除几乎所有的溶解性物质（例如离子、重金属等）。反渗透通常用于去除原水中的溶解性总固体（TDS）。当需要脱盐时，它是一个有效的选择，但也会产生浓缩的废液（图3）。另外，反渗透可以去除其他污染物，如硫酸盐、硝酸盐、农药、重金属和放射性元素。由于反渗透膜的孔径较小，在反渗透之前需要进行某种类型的澄清/过滤预处理过程，除非原水的悬浮物含量本来就较低。

Figure 3 Reverse Osmosis (RO) Membrane Allowing Passage of Water Molecules

图3 反渗透膜允许通过的水中的分子

RO is a pressure-driven process in which almost pure water is forced through a semipermeable membrane and most ions (salts) are left behind.

反渗透膜是一种压力膜，能够通过反渗透膜的几乎是完全纯净的水，几乎所有的离子（盐）都被反渗透膜截留。

The selection of RO membranes is site-specific and depends on feedwater characteristics and overall RO system setup (e.g., low pressure or high pressure, single stage or multistage). Scaling and fouling are two of the biggest concerns when using RO treatment. Scaling occurs when dissolved particles are deposited on the membrane surface, causing it to plug. Fouling is caused when suspended particles accumulate inside the membrane. Both can be minimized with treatment prior to RO. Typically, scaling requires the use of an antiscalant in the RO feedwater that will inhibit the precipitation of ions on the membrane surfaces. Fouling may require coagulation, filtration, or some other type of pretreatment of the RO feedwater. It's important to work with the RO membrane supplier or a third party to determine exactly what type of pretreatment may be required for feedwater at a given site.

反渗透膜的选择是因地制宜的，取决于来水的特性和整个反渗透系统的配置（例如，低压或高压，单级或多级）。使用反渗透膜工艺时，结垢和污染是两个最大的问题。当溶解性的颗粒沉积在膜表面时，会发生结垢，导致膜堵塞。当悬浮颗粒积聚在膜内时，就会造成污染。在反渗透膜开始正常工作之前，这两种情况造成的问题都应该被处理到最小化。通常情况下，结垢需要在反渗透的来水侧中使用抗垢剂，以抑制离子在膜表面的沉淀。膜污染的问题可能需要在膜工艺前增加混凝、过滤或其他类型的预处理。重要的是要与反渗透膜供应商或第三方密切合作，以确定具体项目应该对特定的来水搭配何种预处理工艺类型。

Granular activated carbon (GAC) filtration is an adsorptive process more specialized than conventional filtration (i.e., a film of particulates adheres to the outside surface of media). GAC filters contain thermally or chemically treated organic media (wood, coconut shells, coal, and peat) in a fixed bed or postfilter contactor. They operate by adsorbing material as the water passes through the filter media; contaminants in the liquid phase move to a solid phase as they cling to the surface of the filter media. GAC filters are used to remove organic contaminants with high molecular weights, such as T&O compounds, but they aren't effective at removing microbial contaminants, metals, or ions.

颗粒活性碳（GAC）过滤是一个比传统过滤更有针对性的吸附过程（即由水中的颗粒物形成薄膜状粘附在过滤介质的外表面）。GAC滤池是在一个固定床或后置式的接触滤池中，填充热加工或化学加工处理的有机介质（木材、椰壳、煤和泥炭）。它们的运行方式是在水通过过滤介质时，污染物质被过滤介质吸附，使液相中的污染物通过粘附在过滤介质表面转移到固相中。GAC过滤可用于去除高分子量的有机污染物，如致嗅化合物，但对去除微生物、重金属或离子并不十分有效。

Like conventional filters, GAC filters can be used as biofilters, which can remove metals and other organic contaminants (e.g., T&O compounds and DBPs) that regular GAC filters cannot. This is done by allowing a biofilm to form on the surface of filter media, which converts and/or removes compounds through the metabolic activity of the microorganisms. An advantage of GAC filters compared to conventional filters is that GAC filters remove contaminants that conventional filters allow to pass through. However, GAC media are more expensive, and over time, the media must be regenerated or replaced to maintain adsorptive capacity. This is a serious operational cost that must be factored into the decision to use GAC. A postfilter contactor that acts as a polisher after conventional filtration can be a cost-effective option for removing organics in many cases.

和传统的滤池一样，GAC滤池也可以作为生物滤池来使用，可以去除普通GAC滤池无法去除的金属和其他有机污染物（例如致嗅化合物和消毒副产物）。这是通过在过滤介质表面形成的生物膜来实现的，生物膜通过微生物的代谢活动转化和/或去除化合物。所以与传统滤池相比，GAC滤池的优势在于可以去除传统滤池无法去除通过的污染物。然而，GAC介质更昂贵，而且随着运行时间的推移，必须通过再生或更换介质滤料以保持吸附能力，这是一个占比很大的运行成本，必须在决定使用GAC滤池时就要考虑进去。在许多情况下，在常规的过滤后，作为“抛光”作用布置一个后置的GAC接触池可以成为去除有机物的一个更有成本效益的选择。

Ion exchange (IX) is a chemical process used when low levels of ions need to be removed during treatment. IX can be used to remove cations (positively charged ions like sodium, iron, lead, and calcium) or anions (negatively charged ions like nitrate, sulfate, and chloride). During this treatment process, the undesirable ion is removed and exchanged with a less objectionable ion by passing the water over a resin bed saturated in the ion to be exchanged.

离子交换（IX）是一种在处理工艺中需要去除低浓度离子时使用到的化学工艺过程。IX可用于去除阳离子（带正电的离子，如钠、铁、铅和钙）或阴离子（带负电的离子，如硝酸盐、硫酸盐和氯）。在IX处理过程中，让水通过吸附有某种饱和离子的树脂床，水中希望被去除的离子通过与树脂上的离子交换，达到被去除的目的。

For example, hard water containing excessive amounts of calcium and magnesium ions can be passed through an IX resin bed containing hydrogen or chloride ions. Calcium and magnesium ions will adhere to the resin as hydrogen or chloride ions are released. This process generates a softer water with a small amount of hydrogen or chloride ions that are less objectionable than calcium and magnesium (Figure 4). Over time, the resin bed's performance will degrade as IX occurs, and the resin will need to be regenerated with brine or acid/base. This creates a waste stream that must be disposed of properly. IX can be a good option when treatment is needed to remove a small amount of contaminant but can be costly over time.

例如，含有较高钙和镁离子的硬水可以通过含有氢离子或氯离子的IX树脂床。当氢离子或氯离子被释放时，钙和镁离子被粘附在树脂，通过这个工艺所生产的水比较软，虽然会含有少量的氢离子或氯离子，但相对钙和镁而言不那么“令人讨厌”（图4）。随着运行时间的推移，树脂床的性能会随着离子交换的发生而退化，树脂需要用盐水或酸/碱进行再生。这就产生了一个必须妥善处理的废水。所以当需要处理去除少量的污染物时，IX可能是一个很好的选择，但随着运行时间的推移，成本会很高。

Figure 4 Cationic Ion Exchange Diagram

图4 阳离子离子交换示意

Hard water is softened as magnesium (Mg ²⁺ ) and calcium (Ca ²⁺ ) are exchanged.

硬水通过交换钙镁离子变软。

Ozone (O ₃ ) is a highly reactive gas produced from molecular oxygen (O ₂ ) by corona discharge or vacuum ultraviolet (UV) irradiation. Ozone can be used as a powerful oxidant to oxidize inorganic and organic compounds as well as a disinfectant for removing viruses, bacteria, and protozoa.

臭氧（O ₃ ）是一种通过放电或真空紫外线（UV）照射，由分子氧（O ₂ ）产生的高活性气体。臭氧可以作为一种强大的氧化剂来氧化无机和有机化合物，也可以作为一种消毒剂来杀灭病毒、细菌和原生动物。

Typical purposes of ozone treatment (ozonation) include iron and manganese removal, T&O removal, hydrogen sulfide (H ₂ S) oxidation, color removal, chlorinated DBP reduction, and disinfection. When combined with biologically active filtration (biofiltration), ozonation can remove ~20% of total organic carbon and reduce chlorinated DBP formation potential. Ozone is also known to reduce coagulant doses and improve the coagulation-flocculationsedimentation process.

臭氧处理通常的目的包括去除铁和锰、去除致嗅化合物、氧化硫化氢（H ₂ S）、去除色度、减少氯化消毒副产物，以及消毒。当与生物活性炭过滤（生物过滤）相结合时，臭氧可以去除约20%的总有机碳并减少氯化消毒副产物的生成潜力。众所周知，臭氧还能减少混凝剂的投加量，改善混凝-絮凝-沉淀过程。

Ozone can oxidize and destroy numerous chemicals, including many pharmaceuticals and personal care products. However, certain halogenated (fluorinated, chlorinated, brominated, and iodinated) organics can't be removed/destroyed by ozone. Also, ozone doesn't react with ammonia. Oxidation of organics by ozone can be enhanced by adding hydrogen peroxide (H ₂ O ₂ ), which is called the O ₃ /H ₂ O ₂  advanced oxidation process (AOP) discussed in a later section.

臭氧可以氧化和破坏许多化学物质，包括许多药品和个人护理产品。然而，某些卤化（氟化、氯化、溴化和碘化）有机物不能被臭氧去除/破坏。此外，臭氧不与氨反应。需要通过添加过氧化氢（H ₂ O ₂ ）可以加强臭氧对有机物的氧化作用，这被称为O ₃ /H ₂ O ₂ 高级氧化过程（AOP），会在后面的章节中讨论。

Because ozone is a reactive gas, it can't be stored; it has to be generated on-site using ozone generators (Photo 3a). Liquid oxygen (Photo 3b) or oxygen concentrators are used to supply molecular oxygen to the ozone generators, although dried ambient air can be used as an oxygen source. (Note: The ozone gas concentration will be much lower if ambient air is used. Oxygen content is ~21% in the air.) Traditionally, gas diffusers are often used to introduce ozone gas into water. However, Venturi injectors (Photo 3c) and side-stream pumps are often used in newer water treatment facilities. Depending on a plant's treatment goals, ozone can be injected before rapid mixing (pre-ozone), after sedimentation (intermediate ozone), and/or after filtration (postozone).

由于臭氧是一种很活泼的气体，它不能被储存；它必须在现场用臭氧发生器制备（照片3a）。液态氧（照片3b）或氧气浓缩器被用来向臭氧发生器提供分子氧，干燥的环境空气也可以用作氧源。（注意：如果使用环境空气，臭氧气体浓度会低很多。空气中的氧含量约为21%）。一般的做法，臭氧投加是通过空气扩散器将臭氧气体注入水中。然而，文丘里喷射器（照片3c）和侧流泵在新的设施中经常被使用。根据水厂的具体处理目标，臭氧可以在快速混合前（前臭氧）、沉淀后（中间臭氧）和/或过滤后（后臭氧）时注入。

Photos 3a–d

The ozone system at the water treatment plant in Wylie, Texas, includes ozone generators (3a), liquid oxygen storage tanks (3b), Venturi injectors (3c), and an ozone destruct unit (3d).

照片3a-d 德克萨斯州Wylie市水厂的臭氧系统包括臭氧发生器（3a）、液氧储存罐（3b）、文丘里喷射器（3c）和一个臭氧破坏装置（3d）。

Ozone reacts with bromide (Br ^– ) in water and produces bromate (BrO ^3– ) as a DBP. Bromate is a suspected carcinogen, and its maximum contaminant level in drinking water is 0.010 mg/L. Therefore, bromate monitoring and control is critical for drinking water treatment facilities using ozone. Bromate formation can be reduced by lowering ozone dosage and pH or adding H ₂ O ₂  and chloramines.

臭氧与水中的溴化物（Br ^- ）发生反应，产生溴酸盐（BrO ^3- ），成为一种DBP。溴酸盐是一种可疑的致癌物质，其在饮用水中的最大污染物含量为0.010毫克/升。因此，溴酸盐的监测和控制对于使用臭氧的饮用水处理设施至关重要。溴酸盐的形成可以通过降低臭氧剂量和pH值或添加H ₂ O ₂ 和氯胺来减少。

Ozonation also produces carboxylic acids, ketones, and aldehydes, which are smaller organics that can be effectively removed by biological filtration. Although GAC is a common granular medium for ozone biofiltration, sand and anthracite can act as effective biological filter media. In the presence of certain precursors, ozone is also known to produce nitrosamines. Because ozone is a toxic gas, ambient ozone monitors are required to detect any ozone gas around the ozone system. The current Occupational Safety and Health Administration permissible exposure limit for ozone is 0.1 part ozone per million parts air, averaged over an eight-hour work shift. Ozone destruct units (Photo 3d) are also required to destroy any off-gas from the ozone contactors.

臭氧还会产生羧酸、酮和醛，这些较小的有机物可以通过生物过滤有效地去除。尽管颗粒活性炭是臭氧生物过滤的常见颗粒介质，但沙子和无烟煤也可以作为有效的生物过滤介质。在某些前体物存在的情况下，臭氧也可能会生成亚硝胺。因为臭氧是一种有毒性的气体，所以需要安装环境臭氧监测器来检测臭氧系统周围的臭氧气体浓度。目前，职业安全与健康管理局对臭氧的允许接触浓度限值是每百万份空气中有0.1份臭氧（8小时的工作时间内的平均值）。臭氧破坏装置（照片3d）也被要求配备用来破坏来自臭氧接触器的所有废气。

UV light systems have been used intermittently in water treatment for more than 100?years and have gained popularity in the past few decades. They disinfect water against pathogens (Escherichia coli, Cryptosporidium, Giardia, viruses, etc.), and they sterilize the water through inactivation. In UV systems, water is usually first filtered to remove suspended solids, which increases the effectiveness of UV radiation. UV-C photons (200–280 nm wavelength) are generated in a UV lamp and pass into the water column. Photons pass through the cell walls/membranes of microorganisms and are absorbed by proteins and nucleotides (DNA and RNA). The absorption by nucleotides drives a photochemical reaction that alters the genetic sequence of the microorganism, inactivating it so it can't reproduce.

紫外系统被用于水处理已经有将近100多年了，并在过去的几十年里得到了普及。紫外系统针对病原体（大肠杆菌、隐孢子虫、贾第虫、病毒等）通过灭活作用对水进行消毒。在紫外线系统中，水通常首先被过滤以去除悬浮物，这会帮助增加了紫外线辐射的有效性。紫外线-C光子（200-280纳米波长）在紫外线灯中产生并进入水体。光子穿过微生物的细胞壁/膜，被蛋白质和核苷酸（DNA和RNA）吸收。核苷酸的吸收推动了光化学反应，改变了微生物的基因序列，使其失活，从而无法繁殖。

Bacteria and protozoans are more sensitive to UV radiation than viruses, so virus inactivation requires a higher dose and/or longer contact time. Dosages are normally calculated at UV ₂₅₄  to achieve a 4-log (99.99%) inactivation. A disadvantage to UV disinfection is that it offers no residual like a chlorination/chloramination system does. UV systems often are installed prior to chlorination so the chlorine demand is reduced early, a lower chlorine dose is required, and a chlorine residual remains in the distribution system. An advantage of UV treatment is that no DBPs are formed in this process, unlike in ozonation, but DBPs like halonitromethanes can form after UV treatment when chlorine is added.

细菌和原生动物对紫外线辐射的敏感度比病毒更甚，所以对病毒的灭活需要更高的剂量和/或更长的接触时间。为了达到4-log（99.99%）的灭活效果，剂量通常按UV ₂₅₄ 计算。紫外线消毒的一个缺点是它不像加氯/氯污染系统那样提供持续的残留消毒剂。紫外线系统通常在加氯系统之前安装，这样可以减少对氯的需求，只需要较低的氯剂量保持输配系统中保留一定的余氯即可。与臭氧工艺不同，紫外工艺的一个优点是在这个过程中不会形成消毒副产物，但在紫外工艺处理后再加入氯气时，也会形成卤代甲烷等消毒副产物。

AOPs are a group of oxidation processes in which extremely short-lived, nonselective free radicals (e.g., hydroxyl radicals) are formed and used to oxidize and decompose primarily organic contaminants. AOPs require a combination of different chemical and physical agents, such as ozone, UV, H ₂ O ₂ , and titanium dioxide. Two of the most commonly used AOPs in drinking water treatment are O ₃ /H ₂ O ₂  and UV/H ₂ O ₂ , although the latter is more commonly used in advanced water purification facilities for wastewater reclamation and potable reuse (Photo 4).

高级氧化是一组氧化过程的组合，主要是形成并利用寿命极短的非选择性自由基（如羟基自由基）对有机污染物进行氧化和分解。高级氧化需要不同的化学和物理制剂的组合，如臭氧、紫外线、H ₂ O ₂ 和二氧化钛。饮用水处理中最常用的两种高级氧化工艺的组合是O ₃ /H ₂ O ₂ 和UV/H ₂ O ₂ ，尽管后者更常用于废水回用和饮用水再利用的深度净水设施（图片4）。

Photo 4

UV/H ₂ O ₂  advanced oxidation process reactors are used by the Orange County Water District's Groundwater Replenishment System in Fountain Valley, Calif.

照片4 UV/H ₂ O ₂  高级氧化反应器在加利福尼亚州芳泉谷橙县水地区的地下水补给系统中应用。

The O ₃ /H ₂ O ₂  AOP effectively destroys geosmin and 2-methylisoborneol, which are common T&O compounds. Therefore, many ozone facilities have a provision of H ₂ O ₂  injection to enhance the removal of T&O compounds during the algal bloom season. It should be noted that H ₂ O ₂  must be injected where ozone residual is present; by doing so, the ozone residual will be completely destroyed, and contact time value may be affected. AOPs can also remove many recalcitrant organic contaminants such as 1,4-dioxane. However, certain halogenated organics can't be removed, just like in ozonation. Aside from smaller organics, AOPs generally don't generate DBPs.

O ₃ /H ₂ O ₂ 高级氧化工艺能有效地破坏土臭素和二甲基异莰醇，这些都是常见的致嗅化合物。因此，许多臭氧设施都有投加H ₂ O ₂ 的配置，以加强在藻类繁殖季节对致嗅化合物的去除效果。应该注意的是，H ₂ O ₂ 必须在有余臭氧的工艺段注入。如果这样运行的话，余臭氧可以被完全消耗，接触时间也可能受到影响。高级氧化也可以去除许多难处理的有机污染物，如1,4-二恶烷。然而，某些卤化有机物不能被去除，就像在臭氧工艺中一样。除了较小的有机物外，高级氧化工艺一般不会产生消毒副产物。