Non-Thermal Plasma for Chemical-Free Water Treatment

在水到达水龙头之前，它必须经过一系列处理步骤，使其健康并适合人类饮用。这涉及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显著影响的水的重要特性之一是pH值（水的酸度的量度）。该参数非常重要，如果不能正确控制在一定范围内，处理过程就会失败。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需要pH控制。水和废水处理过程中对pH值控制的要求很广泛，几乎涉及处理过程中的所有步骤。然而，精确控制pH值需要使用大量的化学品，如石灰，苛性钠，盐酸和硫酸。到目前为止，添加化学品来控制pH值是“规范”，这种做法尚未受到挑战或破坏。随着对自然资源的压力越来越大以及严格的环境和安全立法，需要新的可持续工艺来减少化学品的使用及其运输的相关碳足迹。考虑到这一点，需要在这个被忽视的领域进行激进的思考。本提案的主题是一种新的可持续和创新的pH值控制方法。新想法的基本概念是，当水暴露于等离子体时，其pH值会变为酸性或碱性值。该项目将利用这一概念开发一种新的可持续方法，用于控制水和废水处理过程中的pH值，预计该技术将带来一系列额外好处的无化学品处理方法。等离子体在材料加工和半导体制造等各种工业应用中发挥着重要作用。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）是令人感兴趣的，因为所使用的功率主要用于产生等离子体而不加热主体体积。NTP通过两个电极之间的高压放电产生，其中产生大量高能电子、各种反应性分子和自由基物质、离子和光子（例如OH-自由基、臭氧、过氧化氢、UV、冲击波）。当水暴露于这种高度反应性的环境中时，由于这些化学物质的协同作用，发生了一系列用于污染物氧化和水消毒的有用化学物质。去除水中的污染物一直是等离子体在水处理中的应用研究的主要焦点。然而，当应用于水时，NTP不仅产生氧化剂和消毒剂，而且它有可能改变水的pH值，因此它可以用作控制水中pH值的方法。本研究的主要重点是确定在类似于真实的处理过程中预期的条件下控制水中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，然后确定最有效的NTP操作条件，该条件能够在给定的碱性和酸性pH设定值下生产水。然后将使用真实的饮用水和真实的废水沃茨对该系统进行测试。该项目还将评估该系统预计将提供的额外惠益，如去除农药、金属和干扰内分泌的化学品，并根据本研究的结果，确定将决定NTP用于pH值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.