Non-Thermal Plasma for Chemical-Free Water Treatment

在水到达水龙头之前，它必须经过一系列的处理步骤，使它变得健康，适合人类饮用。这涉及到使用大量的化学品来去除溶解和悬浮的污染物以及对水进行消毒。对处理过程的有效性有重大影响的水的重要特性之一是PH值(水的酸度的量度)。这个参数非常重要，如果没有适当地控制在某个范围内，治疗过程就会失败。例如，在水净化和消毒期间，以及在去除废水中的磷或重金属期间，都需要进行PH值控制。水和废水处理过程中的pH控制要求很广，几乎涉及处理过程的所有步骤。然而，准确控制pH值需要使用大量的化学物质，如石灰、烧碱、盐酸和硫酸。到目前为止，添加化学物质来控制酸碱度是一种“规范”，这种做法没有受到挑战或破坏。随着自然资源面临的压力越来越大，以及严格的环境和安全立法，需要新的可持续进程来减少化学品的使用及其运输过程中的碳足迹。考虑到这一点，需要在这个被忽视的领域进行激进的思考。这项提议的主题是一种新的可持续和创新的酸碱度控制方法。这一新想法的基本概念是，当水暴露在等离子体中时，其PH值改变为酸性或碱性。该项目将利用这一概念为水和废水处理过程中的pH值控制开发一种新的可持续方法，该技术有望产生一种具有一系列额外好处的无化学处理方法。等离子体在材料加工和半导体制造等广泛的工业应用中扮演着重要的角色。最近，人们对液体等离子体放电作为传统水处理技术的替代技术的兴趣显著增加。在等离子体的类型中，非热等离子体(NTP)引起了人们的兴趣，因为所用的功率主要是在不加热体积的情况下产生等离子体。NTP是通过两个电极之间的高压放电产生的，在两个电极之间产生大量的高能电子、各种活性分子和自由基物种、离子和光子(例如，OH-自由基、臭氧、过氧化氢、紫外线、冲击波)。当水暴露在这种高度活性的环境中时，会产生一系列有用的化学物质，用于污染物的氧化和水的消毒，这些化学物质的协同作用产生了这些作用。去除水中污染物一直是等离子体在水处理中应用的研究重点。然而，当NTP应用于水中时，它不仅产生氧化剂和消毒剂，而且它还可能改变水的pH，因此可以作为一种方法来控制水中的pH。这项研究的主要重点是确定在与实际处理过程中预期的条件相似的条件下控制水中pH的最佳条件。这将涉及设计和制造具有不同电极配置的三个等离子体原型，然后确定能够在给定的碱性和酸性pH设定值下生产水的最有效的NTP操作条件。然后，该系统将使用真实的饮用水和真实的废水进行测试。该项目还将介绍该系统预计将提供的其他好处，如去除农药、金属和内分泌干扰化学品，并将根据这项研究的结果，确定将决定NTP用于pH控制的商业潜力的关键问题。

Before water reaches the tap, it must go through a range of treatment steps to make it wholesome and fit for human consumption. This involves the usage of large amounts of chemicals to remove dissolved and suspended contaminants and disinfection of the water. One of the important characteristics of water that has significant effect on the effectiveness of the treatment process is pH (a measure of the acidity of water). This parameter is so important to the point that if it is not properly controlled within a certain range, the treatment process fails. pH control is required for example during water clarification and disinfection and also during removal of phosphorus or heavy metals in wastewater. The requirement for pH control during water and wastewater processing is wide and touches almost all steps in the treatment process. However, accurate control of pH requires the use of a significant amount of chemicals such as lime, caustic soda, hydrochloric acid, and sulphuric acid. Until now, addition of chemicals to control the pH is the "norm" and this practice has not been challenged or disrupted. With increasing pressure on natural resources and stringent environmental and safety legislations, there is a need for new sustainable processes to reduce the use of chemicals and the associated carbon footprint with their transportation. With this in mind, radical thinking in this ignored area is required. A new sustainable and innovative approach for pH control is the subject of this proposal. The basic concept of the new idea is that when water is exposed to plasma, its pH changes to either acidic or alkaline values. This project will use this concept to develop a new sustainable method for the control of pH in water and wastewater treatment processes and this technique is expected to lead to a chemical-free treatment method with a range of additional benefits. Plasma plays an important role in a wide variety of industrial applications such as material processing and semiconductor manufacturing. More recently, interest has increased significantly in liquid plasma discharge as an alternative to conventional water treatment techniques. Out of the types of plasmas, non-thermal plasma (NTP) is of interest since the power used is mainly to generate the plasma without heating the bulk volume. NTP is produced by a high voltage discharge between two electrodes where a large amount of high energetic electrons, various reactive molecular and radical species, ions and photons are generated (e.g. OH-radicals, ozone, hydrogen peroxide, UV, shock waves). When water is exposed to this highly reactive environment, a range of useful chemistries for the oxidation of contaminants and disinfection of water resulting from the synergetic effects of these take place. Removal of contaminants in water has been the main focus of research carried out on plasma application in water treatment so far. However, when applied to water, NTP does not only produce oxidants and disinfectants, but also it has potential to change the pH of the water hence it can be used as a method to control pH in water. The primary focus of this research is to determine the optimal conditions for controlling pH in water under conditions similar to those expected in a real treatment process. This will involve the design and fabrication of three plasma prototypes with different electrode configurations, then determine the most effective NTP operating conditions that enables production of water at a given alkaline and acidic pH set values. The system will then be tested using real drinking waters and real wastewaters. The project will also provide an appreciation of the additional benefits that the system is expected to offer such as removal of pesticides, metals and endocrine disrupting chemicals and based on the outcomes of this study, the key issues that will determine the commercial potential of NTP for pH control will be defined.