A TECHNOLOGY totreat domestic sewage,in existence since the'60s, has been put tonew use: treating andrecycling wastewaterfrom public urinals.Mukesh Khare of theIndian Institute ofTechnology in Delhi claims the rotating biological contactor (RBC)process can eliminate foul odour from the urinals, especially in thesummers when there is aperpetual water shortage.
Wastewater from urinals contains both organic matter -dead cells, proteins, urea and sugars- and inorganic substances such asphosphorus and nitrates. To makethe wastewater reusable, the ureacontent, which is responsible for theodour, had to be reduced and thesuspended and dissolved solids hadto be removed. Khare and two of hisstudents decided to use the RBC afterreviewing various options for treatingthe wastewater.
The RBC consists of a series ofplastic discs fixed to a rotatable horizontal shaft and placed in a tank inwhich the wastewater is collected.The discs are partially submerged inthe wastewater and rotated.Microorganisms present in thewastewater bind to the revolvingdiscs, forming a layer of slime orbiofilm. The rotation of the discsserves two purposes: it exposes thebiofilm alternately to the wastewaterand air, facilitating processes thateliminate the odour and also enablesthe thick layers of slime to beslo'ughed off and deposited at thebottom of the tank, from where it can be removed.
Khare and his team have fabricated a simple prototype consisting of atank and RBC discs made of asbestosto keep costs low. Urinal wastewateris collected in a tank and then fed ata steady rate into the RBC system.
Khare says the results of thisexperiment were "very encouraging".He now plans to submit a project tothe department of science and technology for carrying out further studies. Khare intends to construct a pilotrecycling plant for IIT's academic complex.
An innovative aspect of Khare'ssystem is the use of solar energy todrive the RBC discs and pumpwastewater and the treated effluents.He is of the opinion that once thedesign and other parameters of theplant are worked out, the systemcould offer an efficient and inexpensive treatment and recycling systemfor urinal wastewater. He feels thatsuch systems would be ideal in shopping complexes, cinema halls andother non-domestic complexes.