Why is your lab's autoclave wasting water and how to save it?

Steam autoclaves (also known as sterilizers) are common and required equipment in microbiology and animal laboratories today. However, they traditionally consume large amounts of water.

Purchasing a water-efficient steam autoclave is a smart investment that ultimately helps the environment, saves money, and satisfies LEED compliance. For example, a small to mid-sized conventional autoclave may use over a million gallons of water per year. With the growing importance of natural resource conservation, this is a social and economic issue.

Fortunately, a variety of autoclave water conservation strategies have been developed in recent years to meet the need for water conservation. These strategies also helped the lab achieve LEED credits and ASHRAE 198.1-2009 certification for new construction businesses.

Water consumption technology of traditional steam sterilizer

Steam autoclaves consume water for three reasons - steam generation, wastewater cooling and vacuum generation. Let's take a look at each.

#1 Generating Steam: At its core, an autoclave is designed to use pressurized, high-temperature steam to kill any viruses, bacteria, and/or other microorganisms that may be present in the sterilizer chamber. These chambers are usually double-walled vessels with a space called a "jacket" between the walls. When the autoclave is on and idle, the jacket is filled with steam to preheat the unit, ready for operation. Tap or purified water is the source of this vapor. This water consumption source is called the first water source, namely WS1.

#2. Waste Water Cooling: Autoclaves also use water to cool the waste produced. During idle conditions and intermediate sterilizations, steam is always condensed inside the sterilizer and then vented to the floor drain. According to building codes, all waste (or effluent) needs to be cooled to below 140°F before discharge, in large part by introducing raw cold water into the waste stream of the sterilizer, and then immediately discharging the entire mixture to the drain . This cooling water is referred to as the second water source, namely WS2. Unfortunately, many older autoclaves have a "constant drain" of cold water to cool the waste. This means cold water will flow through the steriliser to the drain 24/7 even if the sterilizer is off. The result is the use of 1,500-2,500 gallons of raw cooling water (WS2) per day,

#3. Vacuum Generation: Autoclaves also use water to generate vacuum, as in certain types of loads within the unit, it is necessary to remove air and ensure proper sterilization. This is achieved by evacuating. Autoclaves use a venturi-based water jet or a liquid ring pump (LRP) to create the vacuum. In both systems, the water used to create the vacuum is immediately directed to the drain. This water source will be called the third water source, or WS3. Note that unless a liquid ring pump is specified, most autoclaves come with water jets because of their lower upfront cost. While autoclaves equipped with liquid ring pumps do save water, there are still significant opportunities for further water savings because the water used by vacuum systems is often sent directly to the drain system, which is not an efficient process.

Today's Water Saving Solutions for Traditional Steam Sterilizers 

It is important to note that the amount of water consumed in the autoclave will not be the greatest during steam generation as only 30-50 gallons per day are required. In fact, that figure pales in comparison to the other two autoclave processes, each of which can use 10 to 50 times more water per day. Therefore, to address inefficiencies in wastewater cooling and vacuum generation, some autoclave manufacturers are now offering optional systems and solutions that can significantly reduce water usage. Let's take a look.

Improvements in effluent cooling: Newer autoclaves do not have the same constant exhaust design as older models. To improve the cooling process, the newer system will condition cold water (on and off) only when hot wastewater greater than 140°F is present. The result is an average reduction of 190% in cooling water consumption (WS2) compared to conventional constant displacement units. Likewise, some manufacturers now offer optional systems that can be installed over existing constant emission systems. The system incorporates a combination of condensate cooling and mixing tanks. Specifically, the tank condenses and cools hot waste primarily by using previously cooled waste water, and injects small amounts of cold water into the system only when needed. Such an installation can reduce water consumption by as much as 900,000 gallons per year and reduce water bills by an average of over $6,500 per year (calculation based on national average commercial water + wastewater discharge rates)2. Typical return on investment (ROI) is 3-6 months, as equipment and installation cost between $1,500-3,000.

注意：近年来，使用设备冷却的水循环来冷却废蒸汽和冷凝水已成为越来越受欢迎的选择。这些系统装有热交换器，可将热量从废水转移到冷却器回路中。这些系统依靠冷冻水回路进行冷却。但是，优良作法是使用冷原水的安全备用冷却系统。同样，虽然从理论上讲，这种配置将原水消耗降低到零，但实际上，仍然有少量水用于补充和冷却。

改善真空产生：安装再循环系统-将水抽回真空系统-可以从根本上减少消耗的总水量。再循环系统也将以与前面讨论的冷却水箱用于废水冷却相同的方式冷却冷凝水。这是一个额外的好处。结合这两个因素，再循环系统可以减少水费，节省约85％的净水，或每年节省$ 1,000-1,600。制造商之间这种配置的成本差异很大。因此，投资回报率范围为2-5年。

在节水解决方案时考虑设计

但是，上面提到的每种耗水方案确实需要进行一些设计考虑。让我们来看看每个。 

废水冷却的改进和设计注意事项：结合冷冻水类型系统来解决废水冷却效率低下的问题在很大程度上取决于冷冻水的可及性和家用冷水机组的现有容量。由于某些设计细节，某些高压釜给冷却器带来了巨大负担。因此，了解以下内容重要性无庸赘述：必要的流量，允许的管路压力，最大温度升高和冷冻水的最大压降，以及输入到冷冻水回路中的总热量。

这种情况的一个例子发生在许多冷却器回路在100-300 psig（典型值）之间运行且允许压降在5-10 psig之间的建筑物中。这些冷水机组的主回路温度通常为42°F，回流管路上允许的温度升高为+ 15°F。如果蒸汽灭菌器无法满足这些要求，则可能需要辅助设备，例如减压阀，膨胀/囊罐和冷却器回路上的泵。但是请记住，安装辅助设备可能很难将其包装到可用空间中，并且可能会产生较高的相关成本，例如购买，安装和维护价格标签。

真空发生器的改进和设计注意事项：在考虑安装再循环系统时，请记住要记住有多少可用空间。一些再循环系统和一些热交换器系统会增大高压釜的占地面积，或者需要单独的设备滑道。结果，需要考虑空间需求。

替代方法–无需其他设备或系统

把它关掉：除了对传统的，现有的系统进行修改之外，还有一种非常简单，成本为零且工作量最小的方法，也可以显着减少高压釜的用水量：将其关闭。除了恒定排放的高压灭菌器外，在晚上和周末只需关闭高压灭菌器即可节省大量水。24/7全天候保持高压灭菌。这确实意味着系统始终准备就绪，可以使用，但是维持适当的温暖温度所需的蒸汽意味着不断产生冷凝水。从角度来看，如果仅在工作日内打开高压灭菌器，则可以节省多达70％的冷却水（WS2）。因此，一些制造商在其消毒器上包括自动开关功能。此功能允许控制系统在工作日开始之前对灭菌器进行预热，并在一天结束时和周末关闭蒸汽供应。甚至可以配置更高级的系统，以便每个机构可以在一周的每一天设置不同的开始时间和停止时间。一些高压灭菌器还具有类似于计算机的睡眠模式的功能，如果在指定的时间段内未使用该设备，则蒸汽供应将关闭。

灰水：到目前为止，在高压灭菌器行业中，关于灰水的一次性使用（雨水，湖或井中的非饮用水，或其他工艺产生的废水）已经引起了一些讨论和关注。和基于水箱的冷却。毫不奇怪，由于过滤和生物生长的问题，使用灰水会使项目复杂化，因此通常建议不要将其用途纳入节水策略。

LEED积分和ASHRAE标准

美国绿色建筑委员会的LEED评级系统旨在帮助设施设计者和业主优先考虑保护自然资源而获得认可。从LEED认证到LEED白金级，对项目进行分级和评级。正确配置的正确消毒器可有助于多个类别。分级的示例包括节水和设计创新。有关LEED信用额度的具体金额在很大程度上取决于项目和灭菌器的配置。但是，这种贡献可能是巨大的，不应忽视。

LEED focuses on specific design outcomes and achievements, not to be mistaken for a building code or code. This is why ASHRAE 187.1-2009 is very important. ASHRAE 187.1, titled "Standard for High Performance Design of Green Buildings," is a standard written for ease of incorporation into building specifications and codes. The use of this code has been steadily gaining approval in the construction industry until the last few years. Section 6 "Water Efficiency" is exceptionally important in autoclaves because it prohibits continuous vent cooling of the autoclave and requires the use of a mechanical vacuum system instead of a water spray (venturi) vacuum system. This part also prohibits the use of potable water for primary cooling. Although the scope of the last requirement is limited to HVAC systems,

key points

Steam autoclaves are the primary source of laboratory water. While this depletion can be addressed with more modern systems and installation options, unfortunately there are still thousands of older sterilizers using today's constantly pumping cooling systems. These systems waste more than 10 billion gallons of fresh water each year. For example, a typical campus or facility will often have a variety of autoclave makes and models, from 25+ years old to newer autoclaves, and for one university, more than 100 autoclaves devices are not uncommon. Given this, every laboratory, research facility, and university should conduct a facility survey to determine what type of autoclave is installed and what type of water-saving solution is appropriate.

To calculate potential water savings for your lab, visit our Steam Sterilizer Water Savings page and try the Water Savings Calculator. Want to learn more about how a combined disinfection system can help save water (and money) in your laboratory autoclave? Contact us now.

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