What Causes Sewage Treatment Plant Clogging?

Sewage Treatment Plants play a major role in treating wastewater and ensuring that it is safe for discharge into the environment or reuse. However, one common issue that STPs face is clogging. Clogging can significantly disrupt the functioning of the plant, leading to inefficiencies, delays, and even system breakdowns. In this blog, we’ll explore the primary causes of clogging in STP plants and how to prevent them to ensure smooth and effective wastewater treatment.

Causes of STP plant clogging

Over-accumulation of Solids

The most frequent cause of clogging in an STP plant is over-accumulation of solids in the system. Suspended solids, oil, grease, and organic impurities are present in wastewater and must be removed during treatment. But if solids are not settled or filtered, they accumulate and clog the pipes, filters, and other components of the system.

· Solution: Systematic cleaning of plants like filter cleaning, screen cleaning, and settling tank cleaning can be employed to avoid solids accumulation. Chemical addition to facilitate flocculation and coagulation can also assist in better fine solids removal.

Inadequate Primary Treatment

Primary treatment is used in an STP to filter out the bigger solids from wastewater prior to biological treatment. If the primary treatment fails, the bigger solids will pass through the system and end up in the secondary treatment process. They will plug up biological filters, aeration tanks, and other equipment.

· Solution: See to it that primary treatment plants, including grit chambers, primary settling tanks, and screens, are properly maintained. Maintenance and proper monitoring can make primary treatment more efficient.

High Fats, Oils, and Grease (FOG) Concentration

Fats, grease, and oils are typical commercial food processing plant, restaurant, and residential wastewaters. They plug and solidify the pipes, tanks, and filters of an STP plant if they settle or cool in pipes, tanks, and filters of an STP plant. FOG also creates a heavy scum on the surface of a tank, suppressing oxygen transfer in the bioprocess, and causing plugging.

· Solution: Grease traps and interceptors placed ahead of the wastewater to the STP can be used to cut down on the fats, oils, and greases. The units should be serviced and cleaned regularly so as not to clog the system.

Misuse of Chemicals and Cleaning Materials

Overuse of washing chemicals and chemicals in effluent streams will cause plugging of an STP plant. Reactive chemicals like solvents, bleach, and detergents will interfere with biological treatment either by inactivating useful microorganisms or chemical imbalance. It can cause the formation of sludge, which can cause plugging of the pipes, filters, and pumps.

· Solution: Educate users in the handling of chemicals and cleansing agents. Don't accept wastewater fed into the plant with a high level of toxic chemicals. Screening the incoming wastewater for any indication of pollution can eliminate this problem.

Improper Disposal of Non-Biodegradable Substances

These non-biodegradable wastes like plastics, sanitary towels, paper towel, nappies, etc., other solid wastes are regularly flushed out in the toilets or sewerage instead of their respective dumping grounds. These materials cannot be easily decomposed by the treatment process and hence cause clogging in different parts of the STP system.

· Solution: There should be campaigns to increase the awareness of the public regarding how to dispose of non-biodegradable waste. Apart from this, there should be a trash screen or filter at the inlet that will not allow large particles to enter the STP.

Overloading of the STP System

Overloading takes place when there is more wastewater flow than the capacity of an STP plant can handle. This is caused by heavy rainfalls, where there is excess stormwater that gets mixed with sewage, or by an increase in wastewater volume of domestic or industrial catchments without an increase in flow as otherwise would be the case. An overloaded plant becomes inefficient, and solids, sludge, and other materials settle, leading to clogging.

· Solution: Proper planning and STP design will prevent overloading. Periodic monitoring of flow rates and ensuring that the plant has sufficient capacity to manage peak loads will prevent overloading too. Stormwater diversion systems or temporary holding tanks can be provided to treat additional flow in the event of heavy rainfall or industrial overflows.

Biofilm Build-Up on Equipment

Biofilm refers to a community of microorganisms like bacteria, algae, and fungi that deposit a slimy layer on STP system surfaces. Biofilms are useful to the biological treatment process but cause overgrowth and clogging in the aeration tank, filter equipment, and other equipment. Biofilm deposits reduce the efficiency of the treatment process.

· Solution: Growth of biofilm is regulated by maintenance, cleaning, and proper aeration on a regular basis. Proper environmental conditions (e.g., level of oxygen, pH) must be supplied to avoid overgrowth of biofilm.

Inadequate Sludge Handling

Sludge is used to describe content that is waste after treatment and ought to be drained and disposed of so that it does not clog. Sludge will cause pipes and tanks to clog and form clogging if not drained or properly treated. Bad disposal of sludge will also attract insects and lead to odors.

· Solution: Periodic sludge evacuation, dewatering, and sludge disposal prevent sludge buildup. Sludge monitoring and evacuation operations can be mechanized to make the process clog-free and effective.

Ineffective or Inadequate Pumps and Valves

Valves and pumps are the most important part of the STP system. The pumps cannot pump the water in the system if the pumps are not correctly sized or serviced to meet the volume needed. Similarly, defective valves can cut off flow and lead to plugs in the system.

· Solution: Regular inspection, maintenance, and repair of broken pumps and valves are necessary to provide effective working. Sizing equipment correctly to the STP system capacity is able to prevent mechanical failure clogging.

Conclusion

Clogging of an STP plant may result in a variety of issues from compromise of the treatment effectiveness to failure of a system. Awareness of the common causes of clogging—over-accumulation of solids, fats, oils, and grease, improper disposal of wastes, and overloading of the system—can aid prevention and correction of such issues. Maintenance, inspection, and proper waste management practices are required to maintain an STP plant in a position where it is operating efficiently and effectively. If we keep causes of clogging in mind, we can be in a situation to make sure wastewater treatment is effective and treated water is safe to discharge or recycle.

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