Oil contamination in sewage water comes from various sources. In domestic wastewater, the primary sources of oil contaminations are kitchen waste, restaurant waste, and waste generated from other human activities like car washing, spillage of motor vehicle lubricants, etc. The oil is present in wastewater in two different forms:
- Free-floating Oil & Grease (De-emulsified oil): Free oil float on the surface because of its nature and rise rapidly on the water surface under laminar (calm) condition. Free oil contains droplet size >150 microns. This de-emulsified oil can be removed through various means, e.g., oil skimmer, overflow weir plate, and carbon/organoclay adsorber.
- Emulsified oil: It comes in two categories:
- Mechanically emulsified oil – This oil is stabilized by static charges and other forces. Such oil mixes with water by pumps and other mechanical mixture/equipment. Droplet size varies between 20-150 microns.
- Chemically emulsified oil – When surfactants such as soap, detergent, and other hydrocarbons are present in wastewater along with the free-floating or mechanically emulsified oil, the surfactant and oil react with each other and becomes stabilized. Surfactants have hydrophilic (water-loving) and lipophilic (oil-loving) nature. Hence, they act as a coupling agent between oil and water.
In the treated water from one of our sewage treatment plants (STP), there is 7-15 mg/l oil and grease in mechanically & chemically emulsified form. Since the treated water from STP acts as a feed to the tertiary treatment unit comprising ultra-filtration (UF) units, it results in frequent choking/scaling and decreases the shelf-life of UF membranes. Thus, we are seeking solutions that can remove the emulsified oil from the treated sewage water.
Constraints:
- Since the sewage treatment plant is a biological process, any chemical dosing in the STP process to remove oil and grease shouldn’t affect the biological agents (bacteria) present in the sewage treatment system.
- The treated effluent from the sewage treatment plant is directly fed to the UF unit. There is no space available for introducing a separate chemical dosing unit between the STP and the UF units.
Awards:- INR 3,00,000
Deadline:- 31-03-2023
