What happens in STP Plant and how STP Treat the Sewage water?
STPs are essential in preserving people’s wellbeing and the environment. These facilities treat the wastewater from homes, industries and sewers so that it can be safely discharged into the natural water bodies. In this article, we’ll try to understand the processes that occur in sewage treatment plants and the ways these plants are designed to treat the sewage water.
The Stages of Sewage Treatment
It can be seen that sewage treatment has several stages whereby physical, biological and chemical methods remove impurities like pollutants and pathogens from wastewater. Here are the primary stages of sewage treatment:
Screening: This initial step involves the removal of oversized items like large debris, branches (sticks), leaves, and even plastic. Usually, this is done through the use of coarse screens and grates.
Primary Treatment: The wastewater is allowed to stand in large tanks in this stage. This causes heavy solids known as sludge to sink to the bottom while oil and grease float up to the top. They are removed and treated differently from these solids.
Secondary Treatment: After the primary treatment, the wastewater goes through a biological stage called secondary treatment, where microorganisms, mainly bacteria, decompose organic matter. For example, it can be managed with the help of activated sludge systems, trickling filters, and biological film reactors. The micro-organisms ingest the organic pollutants, converting it into biomass, carbon dioxide, and water.
Tertiary Treatment (optional): In some treatment plants, tertiary treatment is used for further purification of water. It may include additional chemical handling, such as adding chlorine or using UV disinfection to get rid of any other pathogens present.
Sludge Treatment: Primary and secondary treated solids are dewatered to limit their volume prior to being disposed of or reused. Some of the standard methods include aerobic digestion, anaerobic digestion, and mechanical dewatering.
How STPs Treat Sewage Water?
Now, let's delve deeper into how sewage treatment plants work to treat sewage water:
Screening and Removal of Debris: Large objects are first removed when wastewater enters the treatment plant through pipes. Such materials are typically gathered and taken to a landfill.
Primary Sedimentation: During this stage, the sewage is stored temporarily in large sedimentation tanks, that allow heavy components to sink to the bottom, forming primary sludge. The effluent flows to the subsequent stage.
Biological Treatment: Sewage treatment, however, revolves around the secondary treatment. Wastewater contains microorganisms, including bacteria and sometimes algae. They use up the remaining organic material, decomposing it into smaller molecules. This produces a secondary sludge by microbial activity.
Aeration: Many STPs employ various aeration systems in an attempt to preserve appropriate environmental conditions which are suitable for microbial activity. These facilities inject air into the wastewater so microorganisms have enough oxygen to breathe. This process leads to the decomposition of organic pollutants.
Secondary Clarification: The wastewater then passes through secondary clarifiers, where any remaining solids settle out after biological treatment. Typically, the settle solid, or secondary sludge, is then treated or discarded.
Tertiary Treatment (if necessary): In some cases, tertiary treatment is also administered at STPs to enhance water quality. These could include additional clarification, chemical treatment or disinfection procedures to eradicate residual contaminants and pathogens.
Discharge or Reuse: Lastly, the treated effluent is released into natural water bodies such as rivers and lakes and sometimes non-potable use like irrigation or industrial processes.
The raw sewage is converted into clean effluent, safeguarding the environment and public health by the sewage treatment plant. Through a combination of physical, biological, and chemical processes, STPs remove impurities, contaminants, and pathogens, ensuring that wastewater can be safely returned to the environment or reused for various purposes. These treatment facilities play a crucial role in promoting sustainable water management and reducing the impact of human activities on aquatic ecosystems.