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An advanced wastewater treatment is an intermediate step in sewage treatment, undertaken between the primary and final treatment using advanced technologies.
It is a high degree treatment process performed when the sewage produced cannot be efficiently treated by pre-treatment components like a septic tank, trash tank, effluent tank, etc. The method effectively removes nitrogen, fecal coliform, contaminants, solids, and nutrients from the wastewater.
The advanced wastewater treatment components include aerobic treatment units (ATUs), constructed wetlands, lagoons, and media filters. This article explains the main components of an advanced treatment system.
Contents:
1. Aerobic Treatment Units (ATUs)
An aerobic treatment unit is a combination of the following processes:
1. Gross solids removal
2. Aeration
3. Clarification
4. Sludge return
The application of all the four processes together provides a high-quality effluent. They are performed in four separate chambers enclosed in a single tank. A series of tanks are arranged to create an aerobic treatment train, with a provision for wastewater to pass through the tanks.
An ATU system employs biological processes to convert the dissolved and undissolved constituents into gaseous, cell mass and non-degradable forms. The biological processes involve the synthesis and the separation of microbial cells from the treated effluent.
A variety of aerobic and facultative microorganisms are involved in the treatment process. Both of them together decompose the materials in the wastewater. These organisms require an aerobic environment for their survival and to decompose these materials. They also undergo nitrification of ammonia, thus reducing the number of pathogenic organisms.
An ATU system helps to remove substantial amounts of biological oxygen demand (BOD) and total suspended solids (TSS) that are not easily removed by physical processes like sedimentation or the conventional septic system.
2. Constructed Wetlands
A constructed wetland is a basin or a cell that is constructed specifically to treat wastewater. It contains microorganisms, culture media, and plants that serve the function of treating the incoming effluents. If the constructed wetland is supposed to collect subsurface flow, a layer of graded gravel media or porous media is filled in the cell to resist the corrosive and dissolving wastewater characteristics.
Image credits: SSWM
A construction wetland basin consists of an influent distribution device and an effluent collection device. The wastewater is allowed to pass through septic tank treatment before entering the constructed wetland. The wetland also conducts filtration, nitrification, denitrification, and adsorption to remove pathogens and nutrients.
3. Lagoon or Stabilization Pond
Lagoon is used either as a final treatment and dispersal option for wastewater or as one of the methods in advanced pretreatment of wastewater. The technique is preceded by a septic treatment system to remove large solids.
Image Credits: www.lagoons.com
Lagoon is a large basin of wastewater that treats the wastewater through chemical, physical and biological treatment processes. This process converts the wastewater to good quality water that is acceptable to the environment.
Depending on the presence of oxygen in a lagoon system, lagoons can be classified as:
1. Aerobic
2. Facultative
3. Partial-mixed aerated
4. Anaerobic
An aerobic lagoon maintains aerobic condition throughout its depth. They have a depth of 1-3feet, allowing the sunlight to penetrate through the entire water column. A facultative lagoon has two regions, where the top is an aerobic region and the bottom is an anaerobic region. Partial-mixed aerated and anaerobic lagoons are used for industrial and agricultural treatment systems, while aerobic and facultative lagoons are used for onsite treatment systems.
4. Media Filter
A media filter consists of a lined or watertight structure with a media surface for bacteria to perform the treatment process. The media acts as a surface for bacteria to colonize and undergo biochemical and physical processes. The media filter is designed as per predetermined specifications and requirements.
Image Credits: Evoqua Water Technologies
The wastewater from primary treatment is evenly distributed on the media surface. The surface helps to grow bacteria and microorganisms. As the water trickles down through the media, the organisms growing in the media treat the wastewater. The filter base collects the wastewater, which is again sent for treatment or a soil absorption area.
FAQs
An advanced wastewater treatment is an intermediate step in sewage treatment, undertaken between the primary and final treatment using advanced technologies. It is a high degree treatment process performed when the sewage produced cannot be effectively treated by pre-treatment components like a septic tank, trash tank, effluent tank, etc. The method effectively removes nitrogen, fecal coliform, contaminants, solids, and nutrients from the wastewater.
An aerobic treatment unit is a combination of the following processes:
1. Gross solids removal
2. Aeration
3. Clarification
4. Sludge return
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