Wastewater is any water effluent that has been contaminated directly or indirectly by human activity. It could be generated as a result of domestic, agricultural, commercial or industrial use. Management of wastewater has been a challenge humans have had to face for centuries. Traditional societies simply disposed of all wastewater by pouring it away in rivers, lakes, seas and pits. These methods are not viable anymore due to the effects of wastewater on the environment. The high level of pathogens, toxins and pollutants I wastewater require us to treat the water before releasing it into surface or groundwater bodies.
Types of Waste Water
Wastewater varies greatly in toxicity and recyclability based on how or where it has been generated. There are three main types of wastewater, based on the activities that generated it. These categories of wastewater are domestic, agricultural and industrial.
Domestic wastewater is any water effluent generated from direct human contact. It is not limited to household wastewater as the same effluent can be generated in commercial buildings, institutions and industrial facilities. Domestic wastewater basically refers to liquid discharged from toilets, washing clothes/ dishes, cooking and bathing. It can be further classified as grey, black or yellow water. Greywater is the effluent from the non-toilet fixtures such as showers, laundry, dishwashers and bathroom sinks and mostly contains soapy water. Blackwater is water collected from toilets and kitchen fixtures; they contain human faecal sludge, urine and food particles. This kind of wastewater usually has a high concentration of biological pathogens. The third type of domestic water is referred to as yellow water and consists of urine that has been directed separately from other sewage.
Agricultural wastewater is any water runoff from farming activities. In many cases, the wastewater returns to the groundwater without a problem but in large-scale commercial farming, the use of large amounts of fertilizers and pesticides requires the water to be treated before it is released to be absorbed into surface or groundwater channels. This includes water from green houses, large plantations and combined farming communities that use dedicated irrigation facilities and water sources. The benefit of treating this water is that it can be recycled and reused in the same farms.
Industrial Wastewater is the most challenging type of effluent to manage. This is because there is a wide range of contaminants that get mixed up with industrial effluents and separating them from the wastewater requires the use of advanced methods and technology. The following are some sources of industrial wastewater and how they are managed.
Electric Power Plants
Electric power plants generate large volumes of wastewater especially from facilities that generate electricity from fossil fuels such as coal. The wastewater generated from these power plants contains a wide variety of contaminants such as arsenic, nitrogen compounds and metals such as lead, mercury and cadmium. Contaminants that are trapped from other pollution controls such as wet scrubbers, flue-gas desulfurization, fly ash and bottom ash usually find their way into the wastewater. Most of the coal-fired plants use Ash ponds to treat their wastewater. Other treatment methods are also employed including closed-loop ash recycling, chemical precipitation and the use of ion exchange membranes as well as electrodialysis systems.
Food and Beverage Industry
The wastewater generated in the food and beverage industry is mostly biodegradable but due to the occasional chemical content such as antibiotics in foods and pesticides/ fertilisers in vegetables, on-site treatment is necessary before releasing the water into common waterways. Since this industry uses large volumes of water in cleaning processes, proper on-site treatment of the wastewater can help them recycle a lot of it and thus save on overhead expenses. Some of the waste contained in this water includes strong organic waste from animal slaughter such as body fluids and blood, plant organic material, alkali, acids and flavourings as well as preservatives from the food processing plants.
Vehicle maintenance garages, wash bays, bus stations and mechanical workshops all use a lot of industrial oil. Some of the most common water pollutants in the motor vehicle industry are industrial oils. After work is done on the machines, the mechanics normally rinse it off with petroleum and oil which ends up in the wastewater channels. Most of these contaminants including other solvents and lubricants find their way into the sewer system and are often dealt with at the municipal water treatment facilities.
There are several other sources of industrial wastewater and a wide variety of treatment methods have been developed to treat and purify the water before safely releasing it into the environment. With increased urbanisation, the demand for good water treatment facilities is growing at an alarming rate, as a result, the market demand for water filtration and purification devices is going to increase significantly in the coming years.