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Sewage Treatment (STP)
Precipitation softening processes are used to reduce raw water hardness, alkalinity, silica, and other constituents. This helps prepare water for direct use as cooling tower makeup or as a first-stage treatment followed by ion exchange for boiler makeup or process use.
World Technologies is a global leader in the design, construction, and operation of advanced sewage treatment plants (STP), providing innovative solutions for efficient and environmentally responsible wastewater management. Our STPs are engineered to meet the needs of both municipal and industrial clients, ensuring compliance with environmental regulations and contributing to sustainable water resources management.
The screened sewage will then be collected in an Equalization Tank in order to dampen the variation in flow rate and pollutant concentration. Mixing in the Equalization Tank will be provided by coarse bubble diffused aeration. From the Equalization Tank, the equalized sewage will be pumped via feed pumps into Aerobic biological reactors (Aeration Tanks).
The Aeration Tank MLSS considered for design is 3500 – 4,000 mg/l. Air will be provided by fine bubble diffused aeration. Compressed air will be provided by the Air Blowers. WTPL proposes an extended aeration process. The aeration tank will have a low F/M ratio (0.1 kg BOD / kg MLSS-day) and a high Solids Retention Time. This will encourage endogenous respiration and reduce the sludge yield as well as increase the process stability.
Mixed liquor from each Aeration Tank will flow by gravity into the Lamella Clarifier Tank where the mixed liquor suspended solids (MLSS) will be settled. Settled sludge from the bottom of the Lamella Clarifier will be recycled back to Aeration Tank in order to maintain the desired MLSS and excess sludge will be wasted to aerobic sludge digester cum thickener. The Scum from the top of Lamella Clarifier is also fed to excess sludge wasting line. The excess sludge from the clarifier will be collected in a Sludge Holding/Thickening Tank. The supernatant from the Sludge holding tank will be made to flow to the Equalization Tank by gravity.
Sludge from the Sludge Holding Tank will be sent for flocculation in a flocculator Tank via Sludge Transfer Pumps. Poly-electrolyte dosing will be provided for better dewatering results. Flocculated sludge is poured in the special filtration bag made from the ‘water repellent material. After few hours of operation dry solid content of 15% to 20% can be achieved depending upon the nature of the sludge.
After the initial dewatering stage on the machine, the bags are sealed and removed with a special bag trolley and stored in the open. During this second phase, sludge weight and volume continue to reduce regardless of weather condition. After 10 to 15 days of storage, a cake of 50 to 90 % dry solid content is achieved. The concentrate from the system will be returned to the Equalization Tank by gravity.