Sustainable Water Purification. M. R. Islam

In the current scenario, composites have gained popularity in various fields such as constructional, aeronautical, vehicular, biomedical, industrial etc. (Mahajan and Aher, 2012). The use of the said materials in wastewater treatment is becoming a research focus for many. The properties offered by composites include specific strength, processability, and design flexibility. While these composites successfully eliminated Zn²⁺, Ni²⁺, Cu²⁺, Pb²⁺, Hg, etc., each ion is replaced with another component from the adsorbing chemicals that are used in the process. Each of these composites would be considered unsustainable if environmental sustainability were considered (Khan and Islam, 2016). Figure 1.4 shows how chemicals are removed from the contaminated water only to be replaced with toxins, which arise from the purification process.

      Figure 1.4 Water purification process.

The above purification process does not include the impact of using unnatural radiation (e.g. ultraviolet). Although conventional analysis makes it impossible to identify the impact, let alone quantify it, Islam and Khan (2019) Islam et al. (2016) have shown that the effluent water would carry the signature of each unnatural process (energy or mass) used during the purification cycle.

1.5 Introduction to Zero Waste Engineering

      Natural additives have been used for the longest time, dating back to the regime of the Pharaohs of Egypt and the Hans of China (Gove, 1965). However, the renaissance in Europe has given rise to industrial revolution that became the pivotal point for the emergence of numerous artificial chemicals. Today, thousands of artificial chemicals are being used in everyday products, ranging from health care products to transportation vehicles. With renewed awareness of the environmental consequences and more in-depth knowledge of science, we are discovering that such ubiquitous use of artificial chemicals is not sustainable (Khan and Islam, 2016). If the pathways of various artificial chemicals are investigated, it becomes clear that such chemicals cannot be assimilated in nature, making an irreparable footprint that can be the source of many other ecological imbalances (Chhetri and Islam, 2008). Most persistent and bioaccumulative chemicals eventually find their way into our bodies via the food chain. Chemical industries mass produce artificial additives and, therefore, gain the advantage due to the economy of scale, in line with modernization since the industrial revolution.

      Federal regulators have determined that about 4,000 chemicals used for decades in Canada pose enough of a threat to human health or the environment that they need to be subjected to safety assessments (The Globe and Mail, 2006). These artificial additives are either synthetic themselves or derived through an extraction process that uses synthetic products. Even when the source is natural, it may have been contaminated through artificial agents, such as chemical fertilizer, pesticide, etc. These artificial chemicals have a number of hidden adverse side effects. Furthermore, once artificial additives are disposed into the environment, they remain in nature for a very long time. These synthetic products never degrade biologically; they are either pulverized (hence become invisible) or oxidized to produce toxins (Khan and Islam, 2016). On the other hand, natural additives are naturally occurring substances that are considered valuable in their natural form. Most of the natural materials are readily biodegradable, so they have zero waste and they have no long term negative impact. Natural materials are inherently superior to synthetic materials with regard to efficacy and safety in matters related to human health. Any attempt to improve current engineering practices should investigate the possibility of replacing artificial additives with natural ones that are environment friendly and truly sustainable (Khan and Islam, 2007).

1.6 Scope of the Book

      This book takes a holistic approach for water purification. All existing technologies are reviewed and evaluated against a sustainability criterion. Based on the shortcoming of existing technoloigies and overall lifestyle, new line of technologies are proposed. These technologies are all wholly sustainable, meaning they simultaneously meet environmental, economical, and technological challenges. Such technologies are presented for three categories, namely, drinking water, agricultural use, and industrial waste management. It is shown that each of the proposed technologies has the potential to turn waste into asset, thus creating double dividend.

1.7 Organization and Introduction of the Chapters

      The introduction chapter (Chapter 1) introduces the readership such concepts as zero waste engineering, sustainability and others. This is followed by Chapter 2, which discusses water science. With a truly scientific approach, this chapter offers a delinearized history of water science and delineates the role of water in all aspect of life all through history.

      Chapter 3 (Sustainability of Current Water Purification Techniques) presents a detailed account of all major water purification techniques. Each technique is tested for its sustainability.

Chapter 4 (Sustainable Drinking Water Purification Techniques) presents a discussion on what needs to be done in terms of lifestyle adjustment. This is following by the presentation of an array of sustainable technologies, all suitable for drinking water. Recommendations are made for the best options for drinking water.

      Chapter 5 (Sustainable Purification Techniques for Agricultural Wastes) presents a number of options for purifying agricultural waste. The possibility of deriving double dividend by adding value to the waste or by extracting minerals from the waste stream is discussed.

      Chapter 6 (Sustainable Purification Techniques for Industrial Wastes) presents a discussion on how to reset the current ‘technological disaster’ to a sustainable mode. It then presents several options for complete sustainability during industrial waste water treatment. A number of emerging technologies, each having tremendous commercial potentials, are presented.

      Chapter 7 (Summary and Conclusions) lists a summary and key conclusions from each chapters.

      Chapter 8 is a comprehensive bibliography and a list of references.

      Note

      1 * This term does not relate to modern scientific term, which emerges from atomic theory. Rather, it refers to a material in its natural state.