Review of Modern Trends in Water Production, Purification, and Management

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Introduction

Climatic changes resulting from ominous human activities and excessive use of freshwater resources have adversely affected the quality and the quantity of the groundwater reserves. Access to potable water is getting limited globally, specifically across the Middle East and North Africa. Moreover, due to the presence of toxic pollutants freshwater shortage is also felt in Central and Western European countries and Latin America (Bundschuh et al., 2021). The population boom has exacerbated the water deficiency to a further dwindling level of below 1500 m3 per year (per person availability), which is far below the minimum essential standards.

Presently, desalination and brackish water treatment processes, are the major sources of abridging the potable water deficit. Nearly 16000 desalination plants are operational across 177 countries, providing 25 billion gallons of potable water per day.  Israel, UAE, and KSA are some of the countries that meet more than 50% of their industrial, power, irrigation, and domestic uses from desalinated water.  69-73% of such processes rely on membrane-based technologies for desalination and water treatment while 27% use thermal techniques

These prevalent desalination technologies are assessed to be energy-intensive and harmful to the environment, considering domestic and large-scale use. There are several new energy-efficient materials, different technologies, and renewable energy sources that offer promising prospects for environment-friendly and economically viable solutions (Ioannidou et al., 2020).

This paper shall review the environmentally sustainable new developments in water purification processes and novel techniques for the production of water, utilizing new materials and renewable sources, with a view to offering insight into the future water requirements.

New Energy Efficient Water Production and Purification Processes

The environmentally sustainable, latest water purification researches that offer bright prospects to meet future water production and purification technologies are discussed below:

Graphene

Graphene is a two-dimensional carbon molecule and has emerged as a promising base material for water production through desalination. The sleek single-atom thick structure of a perforated graphene filter offers far less frictional losses once seawater thrusts through it, as compared to other polyamide plastic filters. Perforated graphene filters offer hundreds of times better permeability resulting in 50 per cent less energy consumption. (Shao, Zhao, and Qu, 2020). It is important to highlight that the graphene-based membranes were found to be non-permeable in the case of pharmaceuticals, pesticides, endocrine disruptors, and other organic contaminants (Yangali-Quintanilla et al., 2010).

The graphene filters were found to be relatively more resistant to bio-growth as compared to the polyamide filters. Thus, attributing better efficiency to dependent Desalination plants. Moreover, graphene is assessed to be resistant to the damaging effects of chlorine which deteriorates the structural cohesion of ordinary polyamide filters. Hence the graphene-based water purification processes are expected to be more energy-efficient and environmentally friendly. (Shao, Zhao, and Qu, 2020). Graphene can be suitably used as a membrane for distillation and integrated with Photovoltaic solar cells being used to energize the desalination plants even.

Nanotechnology

Water purification systems based on Nanotechnology are modular and assessed to be highly efficient in comparison to the traditional methods employed for water purification. The nanostructures own their efficiency to the great surface-to-volume ratio of integral nanoparticles which enhances the adsorption capability against the influent chemical and biological particles. Such a disposition achieves streamlined isolation of the pollutants and impurities at even very low concentrations.

The nano-membranes and nano adsorbents materials primarily include silver, copper, and zero-valent iron nanoparticles. Carbon-based nanotubes (CNTs) are used as nanomaterials for water purification as well and display promising results for the removal of organic pollutants, inorganic impurities, and biological agents (Arora and Attri, 2020).

Photocatalytic Technology

Purification of water using titanium dioxide as a photocatalyst is gaining prominence in many types of research. The technology is found to be effective in purifying contaminated and polluted water. The technology primarily uses UV (ultraviolet) rays in combination with photocatalyst to eliminate the contaminations and toxins from water.

Titanium dioxide reacts with organic and inorganic compounds such as estrogens, pesticides, dyes, crude oil, and nitrous oxides to form safe coagulants. UV radiation from the sun or other artificial sources is used to segregate the microbes such as viruses and chlorine-resistant pathogens

Photocatalytic technology is best suited for the purification and treatment of surface waters, wastewater, and industrial wastewaters. (Lin et al., 2020)

Solar Harvesting of Atmospheric Humidity

The atmosphere is a huge untapped freshwater reservoir, equivalent to nearly 10 % of surface water resources. The suspension of water molecules in the atmosphere is quite a predominant phenomenon at low RH (relative humidity) levels, prevalent in arid environments. Microporous substances like zeolites are generally used for adsorption of atmospheric humidity however tend to be futile since the material requires a lot of energy to release water. Metal-organic framework (MOF) materials displayed a marked increase in water absorption from the atmosphere under ambient settings over a narrow RH range to harvest water. The procedure employs ambient sunlight to generate enough heat to energize the material for the release of refined water.2.8 litres of water can be harvested per kilogram of MOF per day at as low as 20% RH (Kim et al., 2017)

In yet another concept atmospheric water is harvested without any terrestrial and hydrologic restraint. A super gel composed of hygroscopic polypyrene chloride overlaid with a hydrophilic poly N-isopropyl acrylamide is utilized to prepare a water-absorbing substance. The combined effect of the molecular combination of such hygroscopic and hydrophilicity substances results in an efficient vapour harvesting and storing substance. It also releases water under varied weather conditions. This design as well represents a new approach to revamping the water purification management systems, especially in arid areas and is quite suitable for domestic and individual use. (Zhao et al., 2019)

Collection of Water from Fog

A vertical mesh wire trap is quite supportive for intercepting the fog to collect the fog-water droplets. Various types of materials are used for preparing vertical mesh for example plastic, aluminium, plexiglass, etc. The success of such a system is definitely contingent upon the geographic location and topography of the area. Primarily it suits dry mountainous and coastal regions. Water production from fog is a novel and environment-friendly technology. It entails no major expenditures as well. It is deemed suitable for underdeveloped countries. (Bhushan, 2019)

Water Purification Using Paper and Sunlight

The research entails a procedure, where a sheet of triangular carbon paper is draped over some water, resulting in optimum absorption of water by the paper. On exposure to sunlight, the water evaporates and the resultant pure water is collected separately and the contaminants are left behind. The apparatus can collect about 2.2 litres of water per hour, for every square meter of paper. The research can be further elaborated to develop a functional mechanism for the purification of water collected from open sources at domestic and individual levels (Marchildon, 2018)

The world population is expected to increase by an additional 2 billion people by 2050 (Reiter, 2012). The resultant increase in water requirement is expected to stress out the already strained ecosystem. In such circumstances, wastewater treatment and water reuse are expected to sustain the future urban planning regimes in line with the environmental requirements. The cardinals of future water management and regulations rest on three predominant approaches (1) Potable reuse, (2) Integrated wastewater management, and (3) integrated water and wastewater management (Angelakis et al., 2018).

Potable Reuse

Today, wastewater is no longer viewed as a waste requiring disposal, but as a renewable recoverable source of drinking water, resources, and energy (Tchobanoglous, 2012). Potable reuse is perhaps the most significant future trend expected in the field of water reuse, especially in neighbourhood and high-rise apartments. Potable reuse implies on-spot purification of wastewater for human consumption sequel to various levels of treatment. It is important to highlight that the US EPA acknowledges potable water reuse and has furnished necessary guidelines as well for Water Reuse (US EPA/USAID, 2012).

A similar system for onsite reuse of wastewater has been adopted in San Francisco. It is now mandatory for all new buildings larger than 250,000 square feet to implement the reuse technology. The system collects used water and purifies it to the sub-potable standards for subsequent washing, sanitation, and cooling uses. The system has reduced the water requirements from 50 to 95 per cent in various cases as per the findings of the San Francisco Public Utilities Commission (SFPUC). Future improvements and integration with Artificial Intelligence based smart home systems can further reduce water wastages and improve the efficiency of the water management systems. Moreover, any endeavour to incorporate new materials like graphene and nanomaterials may provide encouraging results for potable reuse, for drinking purposes.

Integrated Wastewater Management

Generally, in urban areas, the wastewater is delivered through extended sewerage channels to a centralized Waste Water Treatment Facility at a remote location. Thus, water reuse in such urban areas is not possible owing to the lack of dual circulation channels. (Tchobanoglous et al., 2014). Moreover, in such circumstances, the operational cost of delivering the treated water back to the point(s) of use often proves inefficient and uneconomical. Thus, it is expected that in the future decentralized arrangements for wastewater management will be performed at or near the point(s) of waste generation and reuse.

On similar lines, an experimental project known as “Janicki Omni Processor (JOP) was set up for a proto-type community system in 2015 to convert the waste accumulated from toilets into pathogen-free drinking water, electricity, and ash. Currently, the project provides clean water and is not only self-sustaining in terms of electricity but generates additional electricity along with non-toxic ash as phosphorus and potassium-rich fertilizer for the soil. (Cashman, 2020).

Integrated Water and Wastewater Management

One water to label all forms of water management is yet another novel concept in the domains of environmental sciences and water engineering works. The concept implies the merger of the Water Department with the Wastewater Management departments at the Municipal level. The rationale bespoke a more thoughtful and cost-effective resolution to meet impending water needs in the future.

Singapore during the 1990s conceptualized Deep Tunnel Sewerage System (DTSS) to meet the needs for Sewerage and Water Management. The project is expected to be completed by 2025 and it revolves around the integration concept. It envisages two deep gravity-run sewer tunnels leading to three centralized water reclamation plants. The treated and reclaimed water will be delivered to factories to produce drinking water sequel to the treatment at the water reclamation plants. Thus, synergizing the effect of the Water and Waste Management departments. (Centre for Liveable Cities, 2020).

Conclusion

New technologies usher in a new day for water production and wastewater treatment systems, in wake of the environmental necessities and human requirements. Combining the advanced water treatment methodology with water purification and the desalinated system will surely prove to be a prospective option to fulfil both obligations. New scientific breakthroughs will surely enhance our understanding of water, wastewater, and their implication for human health. However, water will always remain imperative for life on earth. Therefore, we must holistically conserve and secure our water sources to meet the future water resource management and water reuse challenges effectively.

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