Clarifier tanks are a part of a sewage treatment plant that are used for the continuous removal of solid waste through mechanical means. Clarifiers remove suspended solids from the wastewater for clarification and thickening through the process of sedimentation. The heavier solids, called sludge, will settle at the bottom of the tank whereas the lighter solids, called scum, will float to the top.
How the clarifiers work
Sedimentation also occurs in other tanks of the STP, but use of mechanical methods is what sets the clarifiers apart. The circular clarifier tanks hae a pair os scrapers rotating around the central axis. In some cases, the clarifier tanks have a square shape, and are equipped with conveyor belts. These mechanical devices for solid waste removal move as slowly as possible in order to minimize the resuspension of settled solids. The clarifier tanks are sized to allow a specific water retention time for solids to settle before the water flows onward. The velocity of the flowing water is slowed down using baffles at the entrance of the clarifier tanks. The overflow weirs uniformly distribute the flow of water over a wide area to prevent resuspension of settled solids.
Factors to address in clarifier maintenance
Owing to their large size and mechanical components, clarifiers incur considerable purchasing costs. They remove a major part of suspended solids and reduce the stress of the downstream equipment. If the clarifiers malfunction, it could impact the quality of discharge water, and affect the compliance with norms. The downstream equipment could be dressed. Additionally, a failed clarifier entails significant losses in terms of downtime and repair costs.
3 key factors considered for optimum and cost-effective maintenance of clarifier tanks.
Maintenance of sludge removal system
Complete removal of the sludge from the clarifier is essential for proper functioning of the clarifier. The squeegees sweep all the settled solids from the floor of the clarifier. Due to this heavy work, they need regular inspection and adjustment. Similarly, if the seals placed at various points in the clarifier tank have leakage, the influent can be drawn into the underflow. Such occurrence is known as short-circuiting. Inspect the seals placed in all fixed and moving areas of the clarifier, and promptly replace worn-out seals to avoid leakage.
The low flow rate of water in the clarifier can lead to waste clogging the pipelines and the suction header orifice. Hence, it is important to undertake regular cleaning of the clarifier tanks.
Maintenance of the effluent system
A V-noched weir attached to launder is what makes up a typical effluent system in sewage water treatment plants. It is vital to prevent the growth of algae on the weir and the launder. Generally, operators clean the two components with brushes and chlorine. Such spring brushes are attached to the rotating devices in the clarifier for fast and efficient cleaning. Launders painted with epoxy paint are easier to clean. In some cases, operators install opaque covers on the launders to shield them from light that promotes algae growth.
Clarifier drive
The drive motors in the clarifier provide the force needed to rotate the scrappers in the circular tanks. These scrapers push the settled solids to the center of the clarifier for removal. The drives have several moving parts that need to be lubricated and replaced as they wear out.
Factors to consider in clarifier drive maintenance
Cleaning the drives
Condensed water often collects in the clarifier drives. If not cleaned in time, this condensate could lead the bearing and gear to rust, resulting in premature failure of the drive. Special valves are provided on the drives to drain the condensate. In areas with heavy rainfall and humid weather, the condensate could gather more quickly in the drives. Thus, there is a need to monitor the rate at which this condensate gathers in the drive, and set a specific schedule for cleaning the clarifier drives.
Controlling the torque
Improper torque in the clarifier drives could deeply affect the reliability of the clarifier, and damage the clarifier drive. Monitor and check torque to ensure it stays within specified limits. Solutions such as digital representations of of torque functioning help monitor the torque without any hassle.
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Maintenance of reducers
The reducers and the gear bearing of the clarifier require lubrication. You can give an oil bath to reducers and main gear bearings that run in grease or oil. In most cases, the main gear casing, main bearing, and reducers will have drains located close to them for lubrication.
Lubrication of critical parts
Many critical moving parts make up the clarifiers in wastewater treatment plants, and they need proper lubrication. Bearings must be regularly lubricated. Worn-out bearings begin to make noise or heat up during operations. It must replace in time to prevent serious damage.
In many STPs, the main gear and drive motor directly link to the cycloidal or planetary-gear reducers. This design of STP clarifiers is safer to operate and requires less maintenance than older systems. Lubrication is vital to the proper functioning of these drive chain systems. Otherize, the drive chain will wear out and fail prematurely. The resulting lack of proper tensioning or sprocket misalignment could lead the drive chains to come off the sprockets.
Conclusion
STPs are designed to have a long lifespan. As advanced modern STPs require a high initial investment, many businesses might prefer to keep the older STPs running with timely repairs. However, even though timely repairs keep a wastewater treatment plant running smoothly, they cannot prevent its efficiency from reducing over time. In such cases, ensuring efficient as well as cost-effective wastewater treatment becomes a problem.
Inovar works to resolve the most pressing problems businesses face with setup, installation and maintenance of wastewater treatment plants.
Inovar brings the complete set of water treatment services from feasibility studies to the design, manufacturing, and installation of water treatment systems. Further on, annual maintenance contracts back Inovar STPs to reduce long-term maintenance costs.
Our team works closely with customers to understand their application requirements and suggest a cost-effective water treatment solution. Apart from providing compact and efficient automatic and semi-automatic wastewater treatment plants, Inovar also helps businesses retrofit and update older STPs.
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