Future+Technologies+for+Treatment+of+Wastewater

=** Introduction **=

toc Within the last few decades, concern for pollution and its effects on the environment and health has increased substantially. This is primarily due to global population growth and urban development which has resulted in greater concentrations of pollution within areas inhabited by people. Because of the increase in density of the concentrations of pollution, the harmful consequences on ecosystems have been more obvious than ever. For this reason, these harmful side effects are being documented with more and more frequency, which has also sparked the interest in the “green” movement. The issue of [|water scarcity] has also emerged as a threat and is very much interwoven with pollution and industrialization. After all, water scarcity is not solely dependent on the amount of available water. It is also a matter of ensuring that there are proper sanitation systems in place (can’t cook, clean, drink, etc... without clean water). The exponential growth of these issues has scientists and engineers focusing on environmentally friendly alternatives to harvest and purify wastewater. Wastewater is defined as water that contains a “complex mixture of natural organic and inorganic materials as well as man-made compounds” (Abdel-Raouf, 2012). Horan states that sources for wastewater include “Discharge of either raw or treated sewage from town and villages; discharge from manufacturing or industrial plants; run-off from agricultural land; and leachates from solid waste disposal sites” (Horan, 1990). Even though wastewater can stem from agricultural practices, it can also infiltrate non-polluted agricultural regions and fisheries which greatly alters the health of livestock. Wastewater also deteriorates oceans and bodies of freshwater once it reaches this point in the water cycle. Traditional methods of purifying and ensuring wastewater is kept to a minimal (water treatments plants, using chlorine, etc…) are often extremely costly and require large amounts of energy to power. As well as this, water treatment plants are counterproductive in that they produce secondary waste that further contaminates the planet. Current development in wastewater technology is attempting to correct these flaws. These advancements are also attempting to make the process more affordable, more environmentally friendly, and so that it requires less manpower to operate. Future purification technologies that will be explored in this review include the use of microalgae, ultraviolet light, and aquatic plants.

=** Algal Water Treatment **=

There are numerous technologies that have the potential to increase the environmental friendliness of traditional water treatment plants, but they do not solve the problem. For example, adding solar panels, wind mills, or using biogas will obviously be better for the environment but it will not eliminate the secondary waste or increase affordability. Unfortunately, it will reduce affordability because the cost of renewable technology in its current state is often very expensive. However[|, the cost of renewable resources] is quickly falling and will one day surpass traditional resources in affordability. After much research and field testing, micro algae emerged as a potential replacement. Using algae has “traditionally been employed as a [|tertiary process]”, which is the last step in the water treatment process. A traditional “tertiary process [is] aimed at removing ammonia, nitrate, and phosphate”, something that the biological purifiers have been doing remarkably well (Abdel-Raouf, 2012). As well as this, certain species of algae (//Chlorella, Dunaliella, Euglena)// have been discovered to contain metal absorbing qualities that could prove beneficial for removing toxic metals such as lead, zinc, and copper from wastewater. This is crucial because toxic metals “can cause serious health disorders” if they are absorbed into the human body (Barakat, 2010). Water purification also involves the removal of nitrogen, but current methods “remove the majority of the nitrogen as N2 gas, whereas algal treatment retains useful nitrogen compounds in the biomass” (Christenson, 2011). This means that algal treatments offer an affordable, eco-friendly alternative for the “removal of coliform bacteria, reduction of both chemical and biochemical oxygen demand, removal of N and/or P, and….for the removal of heavy metals” from harmful wastewater (Abdel-Raouf, 2012).

=** Ultraviolet Light **=

The application of ultraviolet Light (UV) has also captured the interest of individuals as an alternative water purification method. In some countries such as Canada and the U.K, new federal regulations have been installed that will require water treatment facilities, chemical plants, and other industrial establishments to find other options for purification. In the moment, this might be a drawback for water plant operators, but in the long run it will be highly beneficial. Ultraviolet light has been a strong contender for the replacement of chlorine and other traditional methods because of “modern regulatory pressures, new scientific discoveries, and improvements in UV technology” (Craik, 2007). As well as this, it has been discovered that UV can “inactivate the waterborne protozoan parasites [|Giardia spp.] and [|Cryptospridium spp].” (Craik, 2007). This technology is especially useful for developing countries where clean drinking water is not easily accessible (countries in Southeast Asia and Sub-Saharan Africa). The reason for this is that “centralized drinking water facilities are not available in many places,…so there is a great need for point-of-source treatment methods” (Almquist, 2017). Water scarce regions could utilize this technology to pro vide safer drinking water to their people without any environment impacts. Along with no environmental footprint, other reasons for exploring UV include a “high disinfection efficiency with most viruses, bacteria, and protozoa….and safe operation” (Guo, 2009).

=** Aquatic Plants as an Alternative **=

The use of aquatic plants has also captured world interest because of its vast potential for regions filled with water shortage and pollution. This is because they can remove a “wide range of pollutants such as total suspended solids, dissolved solids, electrical conductivity, hardness,…nitrogen, phosphorus, heavy metals, and many other contaminants” very similarly to micro-algae (Rezania, 2015). Aquatic plants such as [|vetiver grass], [|hyacinth, and water lettuce] seem to be the most capable at absorbing unwanted particles. However, Rezania claims that [|hyacinth] is the most effective aquatic plant for wastewater treatment despite its rapid growth which causes “serious problems for navigation, irrigation, and power generation”. Overgrowth is a large disadvantage for the use of aquatic plants, as it is very likely that algal blooms or other notable events will happen. Controlling and maintaining commercially grown plants on a large scale would be very important in ensuring that useful aquatic plants do not become invasive.


 * Conclusion **

Our environment is changing for the worse due to population growth and industrialization. Pollution and new regulations on greenhouse gas emissions have forced water treatment plants to turn to environmentally conscious alternatives (algae, aquatic plants, UV) to combat this global change. Along with pollution, water scarcity is also a large issue that could be partially solved by these alternatives. For example, using these technologies in Sub-Saharan Africa, where “only 61% of the population have access to clean drinking water” would be highly beneficial (Kpan, 2017). Unfortunately, many of these alternatives are still in the experimental stage and have yet to be used commercially. For many, the idea of using plants or light to filter and clean drinking water is absurd. However, it’s completely realistic to assume that this idea is within reach with the advancements in today’s technology and the desire for environmental impact. Ultimately, ensuring that the algae, plants, etc… filters the water to the same capacity that traditional processes can is of utmost importance for its competitiveness. If it does not offer the same effectiveness as traditional methods it will not survive on the market.

=** References **=

Rezania S. The efficient role of aquatic plant (water hyacinth) in treating domestic wastewater in continuous system. International journal of phytoremediation. 2015; 18(7): 679-685.

Guo M, Hu H, Bolton J. Comparison of low- and medium-pressure ultraviolet lamps: Photoreactivation of //Escherichia coli// and total coliforms in secondary effluents of municipal wastewater treatment plants. Water research. 2009; 43(3): 815-821.

Horan, N.J., 1990. Biological wastewater treatment systems. Theory and operation. John Wiley and Sons Ltd. Baffins Lane, Chickester. West Sussex PO 191 UD, England.

Craik S, Bolton J, Smith, D. Special Issue on application of ultraviolet light to air, water, and wastewater treatment. Journal of Environmental Engineering & Science. 2007; 6(3): 92.

Almquist C, Fyda S, Godby N, Miller M. An investigation on the use of ultraviolet light emitting diodes (UV LEDs) in a plug-flow reactor for water treatment. Environmental progress & sustainable energy. 2017; 36(3): 857-863.

Vetrivel S. Green algae of the genus Spirogyra: A potential absorbent for heavy metal from coal mine water. Remediation. 2017; 27(3): 81-90.

Shamshad I, Khan S, Waqas M. Heavy metal uptake capacity of fresh water algae (Oedogonium westti) from aqueous solution: A mesocosm research. International journal of Phytoremediation. 2016; 8(4): 393-398.

Zhou G, Peng F, Zhang L, Ying G. Biosorption of zinc and copper from aqueous solutions by two freshwater green microalgae //Chlorella pyrenoidosa// and //Scenedesmus obliquus//. Environmental Science and Pollution Research. 2012; 19(7): 2918-2929.

Utomo H, Tan K, Yi Z. Biosorption of heavy metal by algae biomass in surface water. Journal of Environmental Protection. 2016; 7(10): 1547-1560.

Anastopoulos I. Progress in batch biosorption of heavy metals onto algae. Journal of Molecular Liquids. 2015; 209: 77-86.

Omar H. Bioremoval of zinc ions by Scenedesmus obliquus and Scenedesmus quadricauda and its effect on growth and metabolism. International Biodeterioration & Biodegradation. 2000; 50(2): 95-100.

Bulgariu D. Equilibrium and kinetics studies of heavy metal ions biosorption on green algae waste biomass. Bioresource technology. 2010; 103(1): 489-493.

Abdel-Raouf N. Microalgae and wastewater treatment. Saudi journal of biological sciences. 2012; 19(3): 257-275.