According to UNESCO data, in Latin America, for example, wastewater treatment has almost doubled in the last 20 years. Some progress is being made in this area at global level. This implies that its treatment must be more efficient, affordable and sustainable to make better use of this resource. In compliance with Sustainable Development Goal 6 of the United Nations’ 2030 Agenda, the need to increase the percentage of the world’s population that has access to safe drinking water and sanitation will, in turn, lead to increased wastewater discharges. Wastewater: a key resource to address current challenges In Spain, it is commonly reused in agriculture as fertilizer. When this sludge complies with dryness, heavy metal, nutrient and pathogen content requirements, it must be managed with the least impact possible on the environment. This is followed by a process to reduce the amount of water by dewatering, usually with decanter centrifuges. Subsequently, this mixed sludge is digested by aerobic (with air) or anaerobic processes (in a closed tank called a digester) to stabilize the growth of bacteria and to remove them. The main one is the generation of large quantities of sludge, which is extracted in the primary and secondary decanting processes.įirst, the sludge is thickened to reduce the volume of water to be treated, thus optimizing the existing downstream processes. Sludge treatment, WWTP wasteĬertain types of waste are produced as by-products of wastewater treatment. The techniques used include filtration with sand beds or other materials, and disinfection, either using chlorine (usually sodium hypochlorite) or UV light, to reduce the amount of microscopic living organisms that have been generated in the previous stages. To achieve this, a series of processes are carried out to eliminate pathogenic agents, such as fecal bacteria. Tertiary treatmentĭuring tertiary or chemical treatment, the aim is to increase the final quality of the water so that it can be returned to the environment (sea, rivers, lakes and other hydrographic basins) and, in some cases, used for human activity. It is common in wastewater treatment plants for water treatment to end at this point, when the treated water meets the defined discharge requirements and there are no additional water quality requirements for reuse or further use. This mixture is extracted or flushed out through the lower part of the decanter and the purified water flows out through the upper part without most of the bacteria and solids, giving rise to clarified water. Here, the bacteria that have grown in the previous process precipitate to the lower part of the settling tank, generating a mixture of water and solids, which is called biological sludge. Thus, it consists of removing objects that could damage the plant or the equipment that will be used during the purification process.Ī second or secondary settling process is usual after the biological process. Preliminary or pretreatment, is the first stage of wastewater treatment and is used to prepare water for purification during the following phases. Some of these processes, such as the treatment and management of sludge, are significant because they are complex to manage and are of great interest. In addition, WWTPs also carry out other processes associated with the by-products obtained in the different treatments. These processes are usually divided into four stages known as preliminary, primary, secondary and tertiary treatments. The water entering WWTPs undergoes a series of physical, chemical and biological processes to remove the pollutants it contains. What processes take place in wastewater treatment plants? This process aims to return this resource to the water cycle, either by discharging it into watercourses or reusing it in activities such as agriculture. Wastewater treatment plants (WWTPs), are in charge of collecting water from a populated area or industrial sector and of removing its pollutants. Wastewater or sewage is water whose quality has been compromised by human intervention, and is classified as urban, domestic or industrial, depending on where it comes from. According to the United Nations’ 2017 World Water Development Report, entitled Wastewater – The Untapped Resource, wastewater can be a key resource for meeting the planet’s growing demand for freshwater and raw materials. One of the current challenges at global level is to treat as much wastewater as possible in wastewater treatment plants.
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