A study on environmental effects of wastewater and water treatment plants

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Introduction

Population increase and an increase in human activities contributed to a high demand for clean water and increased amount of wastewater. The increased wastewater has been associated with a number of environmental effects which has strained water treatment plants in their endeavor to release non-pollutants to the environment (Boorse, 2011). Wastewater treatment is the most common pollution control method in the in the world. For instance, the United States has a large network of sewer collection pipeline that collects wastewater from industries, residential areas, institutions, and business, pumping stations and treatment plants. However, research on pollutants in the wastewater has indicated that there has been a considerable increase in chemical pollutants from pharmaceuticals, cosmetics, and pesticides. Water treatment plants, therefore, need to put in place mechanisms to ensure all harmful pollutants are eliminated before the wastewater is released into receiving waters thus reducing environmental pollution and aquatic life.

The purpose of this paper is to outline environmental threats posed by wastewater on animals and aquatic life if it goes untreated. Additionally, the article will demonstrate wastewater treatment process and how they have evolved over time to increase purity level of effluent released into the ocean and other water sources. The treatment processes will demonstrate how useful materials from the wastewater can be recovered and how new energy saving treatment methods have been developed to ensure treated water can be reused for other purposes like industrial use, farming, domestic consumption, and drinking. The research paper comprises of an introduction, body, and conclusion. The introduction introduces the research topic by presenting the thesis statement that the discussion in the body will seek to prove. The conclusion summarizes the ideas brought out in the discussion and how the thesis statement has been proved.

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Background Information

In every community, both solid and liquid wastes are produced from their daily activities. The liquid waste (wastewater) is normally the dirty water that has been used in various applications such as laundry, industries, runoff, and other household applications. Wastewater, in this case, refers to water-carried wastes from residential areas, businesses, industrial establishment, and institutions. If this wastewater is untreated and allowed to accumulate in septic tanks, organic matter in it decomposes producing malodorous gasses. If this wastewater is untreated and released to water bodies, it would contain toxic compounds that can lead to the demise of aquatic life and environmental degradation. Due to adverse environment impacts of wastewater, the collection of such wastewater and subsequent treatment is important to ensure that part of it that is released to the environment is not harmful. Initially, sewage was released into service water bodies such as seas, lakes, and rivers for natural purification. Due to the small volume of sewage compared to water bodies, it was diluted and some of the waste consumed by water organisms and bacteria. With the increased volume of wastewater, there is dire need to treat it before releasing it to water bodies thus helping the natural purification process.

With the increased use of chemicals and pharmaceutical products, they have become one of the main pollutants of the wastewater released from private households, institutions, and factories. Research conducted in the recent past years have revealed a considerable amount of pharmaceutical compounds such as carbamazepine and diclofenac in the aquatic environment (Zhang, 2008). These shows that current water treatment plants are unable to entirely remove them from the effluent released to the water bodies. Pharmaceuticals are currently used in diagnosis and treatment of ailments in animals and humans. If these pharmaceuticals are incorrectly disposed, they find their ways into wastewater where they dissolve thus being discharged to the ecosystem undetected. Therefore, there is a need to incorporate new water treatment methods that will eliminate pharmaceuticals in the effluent wastewater. Pesticides and personal care products are also being released into wastewater in substantial quantities thus there is a need to devise ways to eliminate them before they can be released into water bodies.

Wastewater Treatment Process

Wastewater is treated to make sure it does not pollute the environment it is released into and make it reusable. The wastewater discharged to the sewerage network is composed of solid matter and dissolved pollutants. The treatment process is geared to remove all the solid matter in the wastewater and disinfect the liquid waste to make it reusable. The wastewater is transported from various collection points to the treatment plant using underground tunnels. Conventionally, water treatment is accomplished in two distinct stages known as the primary and secondary stage. In the primary stage, solid waste in the wastewater is removed while in the secondary stage biological processes are used to purify the wastewater further.

Primary Treatment

Once wastewater influent arrives at the treatment plant, it is put into clarifiers where almost half of the pollutant is removed from the wastewater. In the primary stage, wastewater is passed through a screen that removes large floating materials such as sticks and rags. After screening, the sewage is passed into a grit chamber where solid particles such as stones, cinders, and sand are removed. Grit chamber allows these particles settle at the bottom where they can be easily removed. After heavy materials are removed, the wastewater still contains suspended solid materials which are removed through sedimentation. When the sewage passes through sedimentation tanks, its flow is reduced allowing small solid particles to cluster at the ba of the sedimentation tank forming a sludge. The sludge is then pumped and further treated for use in fertilizer manufacturing or incinerated.

Secondary Treatment

The wastewater still contains organic matter that is removed in the secondary treatment stage. This treatment stage uses gravity and biological treatment methods to remove 85 percent of organic pollutant in the wastewater (BWSC, 2017). The sewage is passed through a simple oxygen-activated sludge system. The wastewater is then passed through trickling beds where microorganisms gather and multiply to consume most of the organic matter remaining in the wastewater (Oturan, 2014). The cleaner water now flows into another sedimentation tank where excess microorganisms are removed. In modern water treatment plants, activated sludge are used instead of trickling filters.

After removing organic matter, sodium hypochlorite is added to the wastewater to disinfect it by killing any pathogenic bacteria remaining and reducing the order. If chlorination is done correctly, it can kill 99 percent of pathogenic bacteria found in the effluent. In many cases, de-chlorination is done to remove excess chlorine in the water before it is released into surface water.

Advanced Wastewater Treatment Methods

Due to the shift of economic activities, more difficult to remove pollutants such as pharmaceuticals, pesticides, and heavy metal have become a problem to wastewater treatment systems. Increased water demand and the need for water reuse have also strained water treatment systems calling for alternate treatment options. In addition to using modern treatment methods, mechanisms to prevent pollution such as pretreatment of industrial wastes are being put in place. Users of pharmaceutical products are also encouraged to follow proper disposal directions to ensure they don’t find their way into the sewerage system. Finally, use of other treatment options has been adopted due to the imposition of new regulations that require upgrading of wastewater treatment plants and certain purity level of effluent released to the environment from treatment plants.

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To produce more reusable water from water treatment plants, more advanced treatment methods are being used to remove chemical pollutants. Such techniques include and not limited to filtration, reverse osmosis, distillation, and carbon adsorption (Ganzenko, 2014). These biological treatment techniques are able to remove phosphorous, nitrogen, and other dissolved chemicals from the wastewater (Rybicki, 2007). A combination of these mechanisms is capable of attaining pollution control level required by environmental regulations in place. Effluent from these advanced treatment methods can be used in agricultural activities, recreational purposes, industrial use, and even for domestic use.

Pharmaceuticals, Pesticides, and Personal Care Products in Wastewater Treatment

The presence of pesticides, pharmaceuticals, and personal care products pollutant in the environment have awakened new concerns (Watkinson, 2007). The concern is aggravated by the fact that different chemicals are being used and released into the sewage system machining it hard to remove all of them. For instance, 300 different chemicals are being used in medicine in European Union (EU) only (Ternes, 2004). In addition to the medicinal chemicals, thousands of chemicals make up personal care products. Pharmaceuticals enter the wastewater network through unconventional disposal and metabolic products from humans and animals. Personal care chemicals, on the other hand, enter the wastewater after their normal use such as showering. Chemicals in fertilizers and pesticides also get into wastewater through runoff and stormwater when it rains. When these chemicals are directly released into water bodies, they pose an environmental danger to aquatic life. Due to inability to collect enough data there is no clear understanding of the actual environmental danger posed by these chemical products. Before scientists can come up with comprehensive evidence of risks posed by these trace pollutants, control of these pollutants remain to be the best option we have for now.

Controlling these chemicals from seeping into the environment can be accomplished through proper disposal and removal in wastewater treatment plants. Removal of different chemical pollutants from wastewater depends on the biological treatment stages employed by a treatment plant. The main stages that can be added in biological treatment stage to remove trace pollutants are sorption and biological degradation. These removal mechanisms are applied as wastewater move from primary clarifier into the activated sludge system to remove most chemical pollutants from the wastewater.

Sorption, or mainly absorption, involves the hydrophobic interaction of aromatic and aliphatic compounds with lipophilic cell membrane resulting in an electrostatic reaction of the two compounds. An example of such compound removed through this mechanism is antibiotic ciprofloxacin which was used in the United States. Many acidic pharmaceutical products are negatively charged making it easy to remove them through sorption at a neutral PH using the positively charged amino groups (Corominas, 2013). Biological degradation of trace pollutants, on the other hand, occurs on chemical pollutants when there is a substrate where corresponding bacteria can grow. In biological degradation, the particular bacteria uses the chemical pollutant as a carbon and energy source thus completely using up the pollutant from the wastewater. Pharmaceutical compounds such as contraceptive 17 α-ethinylestradiol and diclofenac are removed from wastewater using biological degradation (Ternes, 2004).

Recovery of Useful Materials from Wastewater

Wastewater treatment firms all over the word are striving to recover all reusable materials from the treatment plant. Water forms the greatest percentage of wastewater and once treated it is released back into the ecosystem in a less harmful form. Effluent from modern treatment plants is clean to the point that they can be reused for agricultural, industrial, and domestic use. Additionally, the biggest percentage of solid waste from wastewater is made of nontoxic organic compounds that are in the form of a sludge. Disposal of such waste is proving problematic thus requiring ways to transform and make them reusable (The United States Patent No. 3,655,39, 1972). There are different ways that the sludge can be put into a useful application such as the production of energy and fertilizers. When the organic wastes are incinerated, the energy produced is used in the production of cement and other building materials. Hydrolysis of these wastes at high temperatures also lead to the production of ethanol, butanol, and other organic compounds (Rulkens, 2007). Incineration with energy recovery leads to the destruction of toxic matters and immobilization of heavy metals into ash and cement. Biogas and other biofuels are also produced from sewage sludge all over the world.

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Apart from incineration, solid waste matter from wastewater treatment plants is recycled to form a different product. Sintering is one of the ways that is used to recycle solid waste matter. Sintering involves compacting weak materials to form strong bonds between them thus producing more strong materials. Sintering is used in ceramic industry to make bricks and tiles (Donatello, 2013). Biosolids removed from grit chambers in primary treatment are further treated to use manufacture of input fertilizers. Sludge from wastewater is rich in nutrients such as phosphorus, nitrogen, potassium, and sulfur which are important in crop growing. Due to the decline of phosphorus resources, fertilizer manufacturing companies have turned to phosphorus-rich wastewater sludge to manufacture fertilizers. Once in production plants, the sludge is thermochemically processed to remove heavy metal and other toxic materials leaving compounds that can enrich the soil for crop production.

Using Treated Water for Other Purposes

Conventionally, treated water from treatment plants is released into the ecosystem by being allowed to flow to water bodies such as rivers, lakes, and seas. In Deer Island Treatment Plant in Boston Harbor, the effluent discharged into the sea through a series of diffusers. In treatment plant that used advanced treatment techniques such as reverse osmosis, distillation, and carbon absorption, the effluent water can be directly used for industrial use, agricultural use, recreational use, and domestic use. This greatly helps in solving water supply problem which is experienced in many areas.

Conclusion

One way of managing the increasing environmental pollution is through effective management of wastewater. However, the release of pharmaceutical, pesticides, and personal care products have posed a serious problem to wastewater treatment firms. Traditional treatment methods have been found ineffective in handling such chemical pollutants thus requiring new treatment techniques to ensure such pollutants are not released to the ecosystem where they are a threat to human, animal, and aquatic life. Different biological treatment methods have, therefore, been devised to eliminate growing quantity of pharmaceutical, pesticides, and personal care product contents in wastewater. These methods have effectively been able to reduce environmental pollution caused by effluent from treatment plants. Solid wastes are also recycled to produce energy and used as inputs in fertilizer production companies. Modern water treatment techniques such as reverse osmosis, carbon absorption, and filtration have also increased reusability of effluent water as it is clean enough to be used in industries, recreation facilities, farming, and domestic use.

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  1. Boorse, R. T. (2011). ENVIRONMENTAL SCIENCE. Benjamin Cummings.
  2. BWSC. (2017). Treatment. Retrieved from Boston Water and Sewer Commission Website: http://www.bwsc.org/ABOUT_BWSC/systems/sewer/treatment.asp
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  4. Donatello, S. &. (2013). Recycling and recovery routes for incinerated sewage sludge ash (ISSA). A review. Waste Management, 2328-2340.
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  8. Rulkens, W. (2007). Sewage sludge as a biomass resource for the production of energy: overview and assessment of the various options. Energy & Fuels, 9-15.
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  10. Ternes, T. A. (2004). Peer reviewed: scrutinizing pharmaceuticals and personal care products in wastewater treatment.
  11. Watkinson, A. J. (2007). Removal of antibiotics in conventional and advanced wastewater treatment: implications for environmental discharge and wastewater recycling. Water research, 4164-4176.
  12. Zhang, Y. G. (2008). Carbamazepine and diclofenac: removal in wastewater treatment plants and occurrence in water bodies. Chemosphere, 73(8), 1151-1161.
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