EPA技术说明——臭氧消毒

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臭氧消毒

美国EPA提供了一系列适用于污水处理系统的技术说明文件，供学习参考。

原文出处：EPA

翻译：阮辰旼、何雪妮

Wastewater Technology Fact Sheet

Ozone Disinfection

EPA污水处理技术概况介绍系列——臭氧消毒

概述

Disinfection is considered to be the primary mechanism for the inactivation/destruction of pathogenic organisms to prevent the spread of waterborne diseases to downstream users and the environment. It is important that wastewater be adequately treated prior to disinfection in order for any disinfectant to be effective.

Table 1 lists some common microorganisms found in domestic wastewater and the diseases associated with them.

消毒被认为是灭活/破坏病原体的主要机制，以防止水传播疾病向下游用户和环境蔓延。重要的是，在消毒前要对污水进行充分处理，以便消毒工艺能够发挥功效。表1列出了在生活污水中发现的一些常见微生物以及与之相关的疾病。

Ozone is produced when oxygen (O2) molecules are dissociated by an energy source into oxygen atoms and subsequently collide with an oxygen molecule to form an unstable gas, ozone (O3), which is used to disinfect wastewater. Most wastewater treatment plants generate ozone by imposing a high voltage alternating current (6 to 20 kilovolts) across a dielectric discharge gap that contains an oxygen-bearing gas. Ozone is generated onsite because it is unstable and decomposes to elemental oxygen in a short amount of time after generation.

当氧（O2）分子被外来能量解离成氧原子，随后再与氧分子碰撞形成不稳定的气体--臭氧（O3）时，臭氧形成，可用于消毒污水。大多数污水处理厂通过对含氧气体的电介质放电间隙施加高压交流电（6至20千伏）来产生臭氧。臭氧是在现场产生的，因为它是不稳定的，在产生后很短的时间内就会分解为氧原子。

Ozone is a very strong oxidant and virucide. The mechanisms of disinfection using ozone include:

• Direct oxidation/destruction of the cell wall with leakage of cellular constituents outside of the cell.

• Reactions with radical by-products of ozone decomposition.

• Damage to the constituents of the nucleic acids (purines and pyrimidines).

• Breakage of carbon-nitrogen bonds leading to depolymerization.

臭氧是一种非常强的氧化剂和杀毒剂。臭氧的消毒机制包括：

- 直接氧化/破坏细胞壁，让细胞成分泄漏到细胞外。

- 与臭氧分解的自由基副产物发生反应。

- 对核酸的成分（嘌呤和嘧啶）造成损害。

- 碳氮键的断裂导致解聚。

When ozone decomposes in water, the free radicals hydrogen peroxy (HO2) and hydroxyl (OH) that are formed have great oxidizing capacity and play an active role in the disinfection process. It is generally believed that the bacteria are destroyed because of protoplasmic oxidation resulting in cell wall disintegration (cell lysis).

当臭氧在水中分解时，形成的过氧化氢自由基（HO2）和羟基自由基（OH）具有很大的氧化能力，在消毒过程中发挥了积极的作用。一般认为，细菌被杀灭是因为原生质氧化导致细胞壁瓦解（细胞裂解）。

The effectiveness of disinfection depends on the susceptibility of the target organisms, the contact time, and the concentration of the ozone. A line diagram of the ozonation process is shown in Figure 1. The components of an ozone disinfection system include feed-gas preparation, ozone generation, ozone contacting, and ozone destruction.

消毒的效果取决于目标生物体的敏感性、接触时间和臭氧的浓度。臭氧消毒过程的路线图见图1。

臭氧消毒系统的组成包括原料气体的准备、臭氧的发生、臭氧的接触、以及臭氧消毒系统。

Air or pure oxygen is used as the feed-gas source and is passed to the ozone generator at a set flow rate. The energy source for production is generated by electrical discharge in a gas that contains oxygen. Ozone generators are typically classified by:

• The control mechanism (either a voltage or frequency unit).

• The cooling mechanism (either water, air, or water plus oil).

• The physical arrangement of the dielectrics (either vertical or horizontal).

• The name of the inventor.

空气或纯氧被用作原料气源，并以设定的流速进入臭氧发生器。臭氧的制备是依靠在含有氧气的气体中放电来发生。臭氧发生器通常按以下方式分类。

- 控制机制（电压或频率）。

- 冷却机制（水，空气，或水与油一同）。

- 电介质的物理排列 (垂直或水平）。

- 发明者的名字。

However, generators manufactured by different companies have unique characteristics but also have some common configurations.

当然，不同供应商制造的臭氧发生器都有各自的特点，但也有一些共同的配置。

The electrical discharge method is the most common energy source used to produce ozone. Extremely dry air or pure oxygen is exposed to a controlled, uniform high-voltage discharge at a high or low frequency. The dew point of the feed gas must be -60℃ (-76℉) or lower. The gas stream generated from air will contain about 0.5 to 3.0% ozone by weight, whereas pure oxygen will form approximately two to four times that concentration.

放电法是用于生产臭氧的最常见的方法。极度干燥的空气或纯氧暴露在一个受控的、均匀的高频或者低频的高压放电中，进料气体的露点必须是-60℃（-76℉）或更低。以空气为原料进行发生，将获得含有约0.5至3.0%的臭氧（按重量计算）的混合气体，而以纯氧为原料发生所获得的产品将比前者提高约2至4倍的浓度。

After generation, ozone is fed into a down-flow contact chamber containing the wastewater to be disinfected. The main purpose of the contactor is to transfer ozone from the gas bubble into the bulk liquid while providing sufficient contact time for disinfection. The commonly used contactor types diffused bubble (co-current and counter-current) are positive pressure injection, negative pressure (Venturi), mechanically agitated, and packed tower. Because ozone is consumed quickly, it must be contacted uniformly in a near plug flow contactor.

通过发生器发生后，臭氧被送入含有待消毒的污水的下向流接触池。接触池的主要目的是将臭氧从气泡中转移到液体中，同时为消毒提供足够的接触时间。在接触池中常用的气泡扩散类型（同流和逆流）有正压喷射、负压（文丘里）、机械搅拌和填料塔。因为臭氧消耗得很快，所以必须在接近塞流的接触器中均匀地接触。

The off-gases from the contact chamber must be treated to destroy any remaining ozone before release into the atmosphere. Therefore, it is essential to maintain an optimal ozone dosage for better efficiency. When pure oxygen is used as the feed-gas, the off-gases from the contact chamber can be recycled to generate ozone or for reuse in the aeration tank. The ozone off-gases that are not used are sent to the ozone destruction unit or are recycled.

臭氧接触池中逸失的尾气必须在释放到大气中之前进行处理以消除任何剩余的臭氧。因此，（注入臭氧接触池）必须保持一个最佳的臭氧浓度，以提高反应效率。当使用纯氧作为原料气体时，臭氧接触池的尾气可以被回收用以继续产生臭氧或在曝气池中重新使用，而其他臭氧尾气被送到臭氧处理装置或被回收利用。

The key process control parameters are dose, mixing, and contact time. An ozone disinfection system strives for the maximum solubility of ozone in wastewater, as disinfection depends on the transfer of ozone to the wastewater. The amount of ozone that will dissolve in wastewater at a constant temperature is a function of the partial pressure of the gaseous ozone above the water or in the gas feed stream.

关键的工艺控制参数是浓度、混合和接触时间。臭氧消毒系统力争使臭氧在污水中的溶解度达到最大，因为消毒消毒取决于臭氧在污水中的转移。在恒温条件下，能溶解在污水中的臭氧量是水面上的气态臭氧分压或进气流中的臭氧分压的函数。

It is critical that all ozone disinfection systems be pilot tested and calibrated prior to installation to ensure they meet discharge permit requirements for their particular sites.

至关重要的是，所有的臭氧消毒系统在安装前都要进行中试验证和校准，以确保它们符合特定地点的排放许可要求。

适用范围

Ozone disinfection is generally used at medium to large sized plants after at least secondary treatment. In addition to disinfection, another common use for ozone in wastewater treatment is odor control.

臭氧消毒一般用于中型到大型的水厂，至少在二级处理后使用。除了消毒功能之外，臭氧在污水处理中的另一个常见用途是控制气味。

Ozone disinfection is the least used method in the U.S. although this technology has been widely accepted in Europe for decades. Ozone treatment has the ability to achieve higher levels of disinfection than either chlorine or UV, however, the capital costs as well as maintenance expenditures are not competitive with available alternatives. Ozone is therefore used only sparingly, primarily in special cases where alternatives are not effective.

在美国，臭氧消毒是使用最少的方法，尽管这种技术在欧洲已经被广泛应用了几十年。臭氧有能力达到比氯气或紫外线更好的消毒水平，然而，其投资成本以及维护费用与现有的替代品相比没有竞争力。因此，臭氧的使用非常少，主要是在其他替代工艺无效的特殊情况下被应用。

优点与缺点

Advantages

• Ozone is more effective than chlorine in destroying viruses and bacteria.

• The ozonation process utilizes a short contact time (approximately 10 to 30 minutes).

• There are no harmful residuals that need to be removed after ozonation because ozone decomposes rapidly.

• After ozonation, there is no regrowth of microorganisms, except for those protected by the particulates in the wastewater stream.

• Ozone is generated onsite, and thus, there are fewer safety problems associated with shipping and handling.

• Ozonation elevates the dissolved oxygen (DO) concentration of the effluent. The increase in DO can eliminate the need for reaeration and also raise the level of DO in the receiving stream.

优点

- 臭氧在杀灭病毒和细菌方面比氯气更有效。

- 臭氧处理过程只利用了很短的接触时间（大约10到30分钟）。

- 臭氧处理后没有需要清除的有害残留物，因为臭氧会迅速分解。

- 臭氧处理后，除了那些被污水中的颗粒保护的微生物外，没有任何微生物重新生长。

- 臭氧是在现场发生的，因此，与运输和处理有关的安全问题较少。

- 臭氧处理提高了出水的溶解氧（DO）浓度。溶解氧的增加可以减少再曝气的需要，也可以提高受纳水流中的溶解氧水平。

Disadvantages

• Low dosage may not effectively inactivate some viruses, spores, and cysts.

• Ozonation is a more complex technology than is chlorine or UV disinfection, requiring complicated equipment and efficient contacting systems.

• Ozone is very reactive and corrosive, thus requiring corrosion-resistant material such as stainless steel.

• Ozonation is not economical for wastewater with high levels of suspended solids (SS), biochemical oxygen demand (BOD), chemical oxygen demand, or total organic carbon.

• Ozone is extremely irritating and possibly toxic, so off-gases from the contactor must be destroyed to prevent worker exposure.

• The cost of treatment can be relatively high in capital and in power intensiveness.

缺点

- 低剂量的臭氧可能无法有效灭活一些病毒、孢子和囊肿。

- 臭氧是一种比氯气或紫外线消毒更复杂的技术，需要复杂的设备和有效的接触系统。

- 臭氧具有很强的反应性和腐蚀性，因此需要耐腐蚀的材料，如不锈钢。

- 对于悬浮物（SS）、生化需氧量（BOD）、化学需氧量或总有机碳含量高的废水来说，臭氧处理并不经济。

- 臭氧具有极强的刺激性，而且可能有毒，因此必须收集处理接触池的废气以防止工人接触。

- 处理的成本在投资和电耗方面可能相对较高。

表现

Belmont and Southport Wastewater Treatment Plants in Indianapolis, Indiana

印第安纳波利斯的贝尔蒙特和南港污水处理厂

In 1985, the City of Indianapolis, Indiana, operated two-125 million gallons per day (mgd) advanced wastewater treatment plants at Belmont and Southport using ozone disinfection. The rated capacity of the oxygen-fed ozone generators was 6,380 pounds per day, which was used to meet geometric mean weekly and monthly disinfection permit limits for fecal coliforms of 400 and 200 per 100 ml, respectively.

1985年，印第安纳州印第安纳波利斯市在贝尔蒙和南港工厂运行了两个每天1.25亿加仑（mgd）的深度污水处理厂，并使用了臭氧消毒。臭氧发生器的额定发生量为每天6,380磅，用于满足出厂水每周和每月的几何平均消毒许可限制标准，即每100毫升出水中的粪便大肠菌群分别为400和200。

Disinfection was required at both Indianapolis treatment plants from April 1 through October 31,

1985. Equipment performance characteristics were evaluated during the 1985 disinfection season and consequently, disinfection performance was optimized during the 1986 season. The capital cost of both ozone systems represented about 8% of the plants' total construction cost. The ozone system’s Operation and Maintenance (O&M) cost represented about 1.9% and 3.7% of the total plant O&M costs at the Belmont and Southport plants, respectively.

1985年4月1日至10月31日期间，印第安纳波利斯的两个处理厂都需要进行持续的消毒。通过对1985年的消毒季节设备的性能特点进行的评估，在1986年的消毒季节对设备消毒性能进行了优化。两个臭氧系统的投资成本约占工厂总建设成本的8%。臭氧系统的运行和维护（O&M）费用分别占贝尔蒙和南港工厂总运行和维护费用的1.9%和3.7%。

In 1989, a disciplined process monitoring and control program was initiated. Records indicated a significant effect on process performance due to changes in wastewater flow, contactor influent fecal coliform concentration, and ozone demand.

1989年，一项严格的工艺监测和控制计划启动。记录显示，由于污水流量、接触池进水粪便大肠菌群浓度和臭氧需求的变化，对工艺性能产生了重大的影响。

Previously, ozone demand information was unknown. Several studies were conducted to enable better control of the ozone disinfection process. These included the recent installation of a pilot-scale ozone contactor to allow the plant staff to measure ozone demand on a daily basis. Also, tracer tests were conducted to measure contactor short-circuiting potential. Results demonstrated a noticeable benefit of adding additional baffles. Results also indicated operating strategies that could maximize fecal coliform removal, such as reducing the number of contactors in service at low and moderate flow conditions.

在此之前，臭氧需求量的信息是未知的。为了更好地控制臭氧消毒过程，进行了一些研究。这些研究包括最近安装了一个试验规模的臭氧接触器，使工厂工作人员能够每天测量臭氧需求量。此外，还进行了示踪试验以测量接触器内的短流情况。结果表明，增加额外的挡板有明显的好处。结果还显示了可以最大限度地去除粪便大肠菌群的操作策略，如在低和中等流量条件下减少接触器的数量。

运行和维护

Ozone generation uses a significant amount of electrical power. Thus, constant attention must be given to the system to ensure that power is optimized for controlled disinfection performance.

臭氧发生器需要使用大量的电能。因此，必须持续关注以确保电能的应用得到优化，从而实现可控的消毒性能。

There must be no leaking connections in or surrounding the ozone generator. The operator must on a regular basis monitor the appropriate subunits to ensure that they are not overheated. Therefore, the operator must check for leaks routinely, since a very small leak can cause unacceptable ambient ozone concentrations. The ozone monitoring equipment must be tested and calibrated as recommended by the equipment manufacturer.

臭氧发生器内部或周围不能有泄漏的漏点。操作员必须定期监测相应的子单元，以确保它们不会过热。因此，操作人员必须定期检查是否有泄漏，因为一个非常小的泄漏就会造成不可接受的环境臭氧浓度。臭氧监测设备必须按照设备供应商的建议进行测试和校准。

Like oxygen, ozone has limited solubility and decomposes more rapidly in water than in air. This factor, along with ozone reactivity, requires that the ozone contactor be well covered and that the ozone diffuses into the wastewater as effectively as possible.

像氧气一样，臭氧的溶解度有限，在水中比在空气中分解得更快。由于这个因素，加上臭氧的反应特性，要求臭氧接触池应被很好地覆盖，并使臭氧尽可能有效地扩散到污水中。

Ozone in gaseous form is explosive once it reaches a concentration of 240 g/m3. Since most ozonation systems never exceed a gaseous ozone concentration of 50 to 200 g/m3, this is generally not a problem. However, ozone in gaseous form will remain hazardous for a significant amount of time thus, extreme caution is needed when operating the ozone gas systems.

气态的臭氧一旦达到240克/立方米的浓度就会产生爆炸。由于大多数臭氧系统的气态臭氧浓度从未超过50至200克/立方米，所以这通常不是一个问题。然而，气态的臭氧将在相当长的时间内保持危险性，因此，在操作臭氧气体系统时，需要特别小心谨慎。

It is important that the ozone generator, distribution, contacting, off-gas, and ozone destructor inlet piping be purged before opening the various systems or subsystems. When entering the ozone contactor, personnel must recognize the potential for oxygen deficiencies or trapped ozone gas in spite of best efforts to purge the system. The operator should be aware of all emergency operating procedures required if a problem occurs. All safety equipment should be available for operators to use in case of an emergency. Key O&M parameters include:

在打开各个系统或子系统之前，必须对臭氧发生器、分配器、接触器、尾气和臭氧破坏器的入口管道进行吹扫。当进入臭氧接触器时，人员必须认识到，尽管尽了最大努力来净化系统，但仍有可能存在残留的臭氧气体。操作人员应了解发生问题时所需的所有紧急操作程序。所有的安全设备都应该供操作人员在紧急情况下使用。关键的运行和管理参数包括：

• Clean feed gas with a dew point of -600C (-760F), or lower, must be delivered to the ozone generator.

• Maintain the required flow of generator coolant (air, water, or other liquid).

• Lubricate the compressor or blower in accordance with the manufacturer's specifications. Ensure that all compressor sealing gaskets are in good condition.

• Operate the ozone generator within its design parameters. Regularly inspect and clean the ozonator, air supply, and dielectric assemblies, and monitor the temperature of the ozone generator.

• Monitor the ozone gas-feed and distribution system to ensure that the necessary volume comes into sufficient contact with the wastewater.

• Maintain ambient levels of ozone below the limits of applicable safety regulations.

- 必须向臭氧发生器输送露点为-60EC（-76EF）或更低的清洁供气。如果供应的气体是潮湿的，臭氧和水分的反应将在臭氧发生器的内部产生一个非常有腐蚀性的冷凝物。臭氧发生器的输出可能会因为氮氧化物（如硝酸）的形成而降低。

- 保持发生器冷却剂（空气、水或其他液体）的必要流量。

- 按照供应商的规格对压缩机或鼓风机进行润滑，确保所有压缩机的密封垫片处于良好状态。

- 在设计参数范围内操作臭氧发生器。定期检查和清洁臭氧发生器、空气供应和电介质组件，并监测臭氧发生器的温度。

- 监测臭氧供气和分配系统，确保必要的量与废水充分接触。

- 保持环境中的臭氧水平低于适用的安全法规的限制。

成本

The cost of ozone disinfection systems is dependent on the manufacturer, the site, the capacity of the plant, and the characteristics of the wastewater to be disinfected. Ozonation costs are generally high in comparison with other disinfection techniques.

臭氧消毒系统的成本取决于供应商商、场地、水厂的能力以及要消毒的污水的特性。与其他消毒技术相比，臭氧的成本通常很高。

Table 2 shows a typical cost estimate (low to medium) for ozone disinfection system used to disinfect one mgd of wastewater. The costs are based on the wastewater having passed through both primary and secondary treatment processes of a properly designed system (the BOD content does not exceed 30 milligrams per liter [mg/L] and the SS content is less than 30 mg/L). In general, costs are largely influenced by site-specific factors, and thus, the estimates that follow are typical values and can vary from site to site.

表2显示了用于消毒1mgd污水的臭氧消毒系统的典型成本估算（低到中）。这些成本是基于污水已经经过了适当设计系统的初级和二级处理过程（BOD含量不超过30毫克/升，SS含量低于30毫克/升）。一般来说，成本在很大程度上受现场具体因素的影响，因此，下面的估计是典型的情况，可能因场地的不同而不同。

Because the concentration of ozone generated from either air or oxygen is so low, the transfer efficiency

to the liquid phase is a critical economic consideration. For this reason, the contact chambers used are usually very deep and covered.

由于从空气或氧气中产生的臭氧浓度很低，向液态的转移效率是一个关键的经济考虑。出于这个原因，所使用的接触池通常很深，而且有盖。

The overall cost of an ozonation system is also largely determined by the capital and O&M expenses. The annual operating costs for ozone disinfection include power consumption, and supplies, miscellaneous equipment repairs, and staffing requirements.

臭氧系统的总体成本也主要由资本和运行和维护费用决定。臭氧消毒的年度运行成本包括电力消耗，以及耗材、杂项设备维修和人员需求。

Another consideration for the cost is that each ozonation system is site specific, depending on the plant’s effluent limitations. Chemical suppliers should be contacted for specific cost information.

成本的另一个考虑因素是，每个臭氧系统都是因地制宜的，取决于工厂的污水排放限值。应与化学品供应商联系以获得具体的成本信息。

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