猪场饮用水生物安全（三）- AASV 2020

来源：猪译馆 2020-05-26 15:16:57| 查看：次

译者的话<<

化学消毒剂的功效可以通过了解消毒剂的残留浓度和影响其消毒性能的因素(主要是温度、pH值、接触时间和所要达到的消毒水平)来预测。这一关系通常被称为CT，CT中的“C”是消毒剂的残留浓度（以mg/L计量），“T”是消毒剂接触时间（以分钟计量），这两个因素在特定条件下（如温度和pH值）针对特定的微生物就形成了CT这一理念。

CT可用于验证所用的消毒剂最佳消毒效果的浓度(毫克/升)、接触时间(分钟)和水的物理特性，如温度和pH值，以及用于日常确认和记录这些参数的方法（通过接受的标准方法，即美国标准试验方法进行验证）。

猪场饮用水生物安全（三）- AASV 2020

Groundwater Biosecurity for Livestock Production and Husbandry (Part 3) – AASV 2020

接上文......

公共供水系统的运营模式

Operative model for PWS’s<<

在安装消毒系统之前，公共供水系统需要向国家监管机构提交一份工程计划供审查和接受。这个计划必须包括设备规格和该设备已通过在一定的水环境、物理特性和流速范围内能达到并维持最低4 Log¹⁰(99.99%)的灭活/去除病毒的能力的验证（或者可以通过其他方式进行的验证）*。还要理解对病原体的去除率和/或灭活率越高，就意味着维持安全供水的可能性也越高。在公共供水系统行业中，4 Log¹⁰(99.99%)的去除率/灭活率在性能(生物安全性)、成本和复杂性方面达到了最大的平衡，并在一定程度上（可接受水平）可以防止病原体进入和/或在公共饮用水配水系统中繁殖扩散。

In advance of the installation of a disinfection system a PWS is required submit an engineering plan for State (regulatory) review and acceptance. This plan must include equipment specifications and validation that it has been, or otherwise can be *validated to achieve and sustain a minimum of 4 Log10 (99.99%) inactivation/removal of virus over a defined range of water conditions, composition and flow rates. Understanding, higher removal and/or inactivation rates translate to a higher probability of maintaining a safe water supply. Within the PWS industry, 4 Log10 (99.99%) removal/inactivation represents the greatest balance in regard to performance (Biosecurity), cost and complexity with an acceptable level of protection against pathogens from entering and/or proliferating in public drinking water distribution systems.

*在特定的规程下、用特定的方法、按照特定的检测目的而设的标准进行的第三方检测。

*Via third-party testing under protocols, methodologies, and standards accepted specifically for this specific purpose.

这个模型被称为CT概念，并用于验证所用的消毒剂最佳消毒效果的浓度(毫克/升)、接触时间(分钟)和水的物理特性，如温度和pH值，以及用于日常确认和记录这些参数的方法（通过接受的标准方法，即美国标准试验方法进行验证）。

This model is referred to as the CT Concept and is used for validation of disinfection efficacy in response to applied Disinfectant Concentration (mg/L) and Contact Time (minutes) and constituents of water composition, such as Temperature & pH and the means to confirm and record these parameters on a daily basis, via the use of accepted Standard Methods American Standard Test Method (ASTM).

消毒剂

Disinfectants<<

目前可用的消毒剂种类包括氯类、氯胺、二氧化氯和臭氧。氯胺的CT值表明，它是一种很弱的消毒剂，建议把氯胺作为二级消毒使用，但如果该产品会形成消毒副产物并造成问题，那么作为一级消毒使用。此外，也可以根据消毒剂的有效性和安全性证明，以及是否能证明对目标病原体的灭活剂量来选择替代消毒剂。

Currently this list includes chlorine, chloramine, chlorine dioxide and ozone. CT values for chloramine illustrate it is a much weaker disinfectant and recommended for secondary vs. primary disinfection or otherwise, if the formation of disinfection byproducts present an issue. Alternative disinfectants can be used based upon proof of validity, safety, and ability to verify applied dose(s) for inactivation of select pathogens.

紫外线照射是一种可以接受的消毒方式。其消毒性能(紫外线光的剂量(UV))取决于多种因素，包括反应器内的水力分布、水流速、水的紫外线透过率、紫外线强度、紫外线灯的输出能力、灯的安装位置、灯的老化程度、污垢和微生物失活的反应速率。通常需要大量的预处理技术以确保消毒性能的均匀性，所以该方法被认为不适合用于养殖场的消毒。

Ultraviolet Irradiation is accepted. Although performance (Ultraviolet (UV) dose) is dependent upon factors, including hydraulic profile within the reactor, flow rate, UV transmittance of the water, UV intensity, lamp output, lamp placement, lamp aging, fouling and microbe inactivation kinetics.56,57 Extensive pretreatment technologies are typically required to ensure consistent performance and considered impractical for livestock applications.

臭氧必须在现场产生，并且使用较为复杂，要进行大量的场地特定工程工作，和复杂并且成熟的操作和维护。此外，在常压条件下，臭氧是气态的、有害的、只能部分溶于水。在没有训练有素的、有执照的水处理设施操作员的情况下，不建议使用该方法消毒。

Ozone must be generated on-site and adds to complexity, extensive site-specific engineering and sophisticated O&M practice. In addition, in atmospheric conditions ozone is gaseous, hazardous and only partially soluble in water. Its use is not recommended in the absence of a trained, licensed water treatment plant operator.

过氧化氢(H₂O₂)目前在畜牧业中用作消毒剂使用。遗憾的是，被指定执行公共饮用水质量标准的美国环境保护署(EPA)并不认为过氧化氢是可行的消毒剂，因此也没有指定它的CT值。笔者也不知道目前是否有第三方（代表过氧化氢制造商和/或分销商）开发了过氧化氢的CT值。

Hydrogen peroxide (H2O2) is currently employed within the livestock industry as a disinfectant. Unfortunately, the EPA, the governing body assigned enforce public drinking water quality standards, does not consider H2O2 a viable disinfectant and finds no reason to assign CT values for its use. Nor is the author aware if CT values have been developed by an independent 3rd party on behalf of a H2O2 manufacturer and/or distributor.

二氧化氯(ClO₂)是爆炸性的。这一特定使运输和储存存在的重大问题。同样，蒸发出液体氯的固体残渣也存在安全问题。二氧化氯必须通过将未稀释的亚氯酸钠与氧化剂(如氯)和/或强酸(如盐酸)在受控和安全的条件下混合而在现场生成。虽然二氧化氯的化学过程可能有了进步，现在可以被安全地运输、储存、注入到水线中、并在足够的浓度下进行测量，但笔者认为，这一进步仍然是未知的。因此，如果您有这种产品，或目前正在使用这种可运输的二氧化氯产品，建议使用美国标准试验方法的标准或美国环境保护署批准的方法(www.hach.com)来验证整个配水系统中二氧化氯的可检测量和浓度是否能达到并维持在目标值。

Chlorine dioxide (ClO2) can be explosive. This presents significant issues in regard to shipping and storage. Similarly, the solid residue left from evaporated liquid ClO2 presents a concern. ClO2 must be generated on-site via mixing undiluted concentrations of Sodium Chlorite with an Oxidant (e.g. Chlorine) and/ or a Strong Acid (e.g. Hydrochloric Acid) in a controlled and safe manner. While there may have been an advancement in ClO2 chemistry and it is now being shipped, stored, injected into a water line safely and measured thereafter at sufficient concentrations, this advancement remains unknown to this author. Accordingly, in the event you have, or currently use such a transportable ClO2 product, the use of an ASTM standard or EPA approved method (www.hach.com) is recommended to verify measurable concentrations of ClO2 are achieved and maintained throughout your plumbing distribution system.

氯化消毒是能导致病原体失活的一种有效的一级消毒剂，也是二级消毒的首选方法。此外，a）无论配水系统的大小，它都是最简单和最便宜的消毒方法；b）在液体状态下，如次氯酸钠，可以用可测量和可控的方法方便地预先注入储水系统中；c）氯化技术非常发达，它是全世界使用最广泛和最众所周知的消毒方法；d）虽然氯溶液的保质期有限（但这一缺点并不抵消前述优点）。

Chlorination is an effective primary disinfectant for the inactivation of pathogens and commonly preferred for secondary disinfection as well. Further, A.) It is the easiest and least expensive disinfection method, regardless of distribution system size; B.) In a liquid state, such as sodium hypochlorite can easily be injected into water in advance of retention systems, measured and controlled; C.) The technology for chlorination is well developed as it is the most widely used and understood disinfection method throughout the world; D.) Although aqueous Cl solutions have a limited shelf life.

CT理念CT concept

化学消毒剂的功效可以通过了解消毒剂的残留浓度和影响其消毒性能的因素(主要是温度、pH值、接触时间和所要达到的消毒水平)来预测⁵⁴。这一关系通常被称为CT，CT中的“C”是消毒剂的残留浓度（以mg/L计量），“T”是消毒剂接触时间（以分钟计量），这两个因素在特定条件下（如温度和pH值）针对特定的微生物就形成了CT这一理念。考虑到消毒剂的衰减，要在水接触系统出口处测量消毒剂的残留浓度。

The efficacy of chemical disinfectants can be predicted based on knowledge of the residual concentration of a disinfectant and factors that influence its performance, mainly temperature, pH, contact time and the level of disinfection required.54 This relationship is commonly referred to as the CT concept, where CT is the product of “C” (the residual concentration of disinfectant, measured in mg/L) and “T” (the disinfectant contact time, measured in minutes) for a specific microorganism under defined conditions (e.g., temperature and pH). To account for disinfectant decay, the residual concentration is measured at the exit of the hydraulic contacting system.

接触时间T采用T₁₀值计算，T₁₀值是指当90%的水达到或超过要求的接触时间时的滞留时间。T₁₀值可以通过理论水停留时间乘以一个系数来估算（该系数是针对储水系统设计的特定系数）。或者，可以进行液压示踪剂试验，以确定在预期的最大流速条件下的实际接触时间。该T值取决于储水量以及与该储水系统设计相关的水力参数。改进水流动力学以达到CT要求要比增加消毒剂浓度和在接触系统内进行物理改造（如实现层流和/或增加水流路径的距离）更有效。在美国环境保护署(EPA)的指南手册中可以找到2 log、3 log和4 log病毒灭活的CT信息⁵⁵。

Contact time T is calculated using a T10 value, defined as the detention time at which 90% of the water meets or exceeds the required contact time. The T10 value can be estimated by multiplying the theoretical hydraulic detention time by a baffling factor, dictated by the design of the retention system. Otherwise, a hydraulic tracer test may be performed to determine the actual contact time under expected maximum Flow (rate) conditions. The T value is dependent on retention volume and the hydraulics related to the design of the retention system. Improving flow hydraulics to achieve CT requirements serves greater utility than increasing the disinfectant concentration and managed with physical modifications (such as to achieve laminar flow and/ or increasing the distance of flow paths) within the contacting system. CT tables for 2 log, 3 log and 4 log inactivation of viruses can be found in an Environmental Protection Agency (EPA) Guidance Manual.55 Selected CT values are presented for a range of 4 Log10 values using disinfectants that have been proven and acceptable for drinking water.

消毒剂量的测定

Determination of disinfection dose<<

Log10灭活的基础是给药剂量，“CT”中的“C”是消毒剂残留(mg/L)，“T”是作用时间或接触时间(分钟)，两者相乘，即：C • T = mg/L • min = 给药剂量

Log10 inactivation is based on the Delivered Dose, “CT” “C” is the disinfectant residual (mg/L), “T” is the exposure or contact time (minutes), multiply them: C • T = mg/L • min = (delivered dose)

CT值可以在美国环境保护署的信息中找到，以确定基于特定监测参数（pH、消毒剂残留和/或温度）的病原体灭活效力：

CT Values can be found in US EPA tables to determine log inactivation based on specific monitored parameters (pH, disinfectant residual and/or temperature):

举例 Example

设定一个每分钟20加仑(gpm)（20加仑约等于75升）的水消毒系统，该系统能持续灭活一个养殖场供水系统中99.99%的所有病毒。使用氯作为首选的消毒剂，pH值为7，温度为10°C。

Design a 20 gallon per minute (gpm) water disinfection system capable of inactivating up to 99.99% of all viruses on a continuous basis within the water supply for a Livestock operation. Chlorine is the preferred disinfectant water pH and Temperature is 7° and 10° C respectively.

从表4可以看出，在pH值为6到9、温度为10°C的水源水中，CT值为6时可以实现游离氯对病毒的4log10灭活。

From Table 4 a CT Value of 6 is identified to achieve 4 Log10 inactivation of virus with Free Chlorine within a source water with a pH between 6 and 9 and a temperature of 10° C.

表4：游离氯对病毒的灭活CT值，pH值为6-9

*饮用水系统所需的安全水平

*Required safety level (barrier) for potable drinking water systems

图5所示的设计消毒系统可以用如下方法进行验证：

A disinfection system of the design as described in Figure 5 can be validated as described below:

水力系数（每分钟20加仑的水消毒系统进行的示踪剂研究）= 0.5

Hydraulic Factor (by Tracer Study @ 20 gpm) = 0.5

水停留净时间(T) =(114加仑/20 gpm)×0.5 = 2.85分钟

Net Hydraulic Retention Time (T) = (114 gallons/20 gpm) ×.5 = 2.85 minutes

计算达到4 Log10灭活所需的游离氯浓度：

(CT值/时间) = mg/L

得到：6/2.85 = 2.11 mg/L

Calculation of Free Chlorine Concentration to achieve 4 Log10 Inactivation:

(CT Value/T) = mg/L

6/2.85 = 2.11 mg/L

图5：储水系统设计示例

根据上述消毒效力参数，当氯溶液以离开最后一个水塔时还能达到至少2.11 mg/L的游离氯浓度的流速进入第一个水塔的入口时，就能实现灭活99.99%的病毒病原体的消毒效力。

With the performance parameters described above, when a chlorine solution enters the inlet of the first tank at a rate that will provide a concentration of Free Chlorine of ≥ 2.11 mg/L in the water exiting the last tank, performance is validated with an inactivation rate of 99.99% against viral pathogens.

安全性较差(99% & 99.9%)的浓度(mg/L)见表5。

Refer to Table 5 for concentrations (mg/L) providing less security (99% & 99.9%).

表5：使用游离氯灭活病毒的CT值，安全性较差

*饮用水系统所需的安全水平(屏障)

*Required safety level (barrier) for potable drinking water systems

**饮用水中的含量限值= 4.0 mg/L

**Concentration limit for potable drinking water = 4.0 mg/L

二氧化氯的参数如表6所示。

The same model applied for Chlorine Dioxide is shown in Table 6.

表6：二氧化氯对病毒的灭活CT值，pH 6.0-9.0

饮用水系统所需的安全水平(屏障)

*Required safety level (barrier) for potable drinking water systems

使用游离氯达到4 Log10病毒灭活所需的CT值(mg/L*min)。水温为10°C, pH值为6.0 - 9.0，CT值为25.1。

水力停留净时间(T)=(114加仑/20 gpm)×5 = 2.85分钟。

CT Value (mg/L*min) to achieve 4 Log10 inactivation of virus with Free Chlorine. With a water temperature of 10° C and a pH between 6.0 and 9.0 = 25.1 Net Hydraulic Retention Time (T)= (114 gallons/20 gpm) × 0.5 = 2.85 minutes.

计算达到4 Log10灭活所需的二氧化氯浓度：

(CT值/时间) = mg/L

得到：25.1/2.85 = 8.81 mg/L

Calculation of Chlorine Dioxide Concentration to achieve 4 Log10 Inactivation:

(CT Value/T) = mg/L

25.1/2.85 = 8.81 mg/L

根据上述消毒效力参数，当二氧化氯溶液以离开最后一个水塔时还能达到8.81 mg/L的浓度的流速进入第一个水塔的入口时，就能实现灭活99.99%的病毒病原体的消毒效力。

With the performance parameters described above, when a Chlorine Dioxide solution enters the inlet of the first tank a rate that will provide a concentration of 8.81 mg/L in the water exiting the last tank, the level of protection is validated with an inactivation rate of 99.99% against viral pathogens.

安全性较差的浓度(99% & 99.9%)如表7所示。

Concentrations providing less security (99% & 99.9%) are shown in Table 7.

表7：使用二氧化氯灭活病毒的CT值，安全性较差