• Investment World
• eWorld
• Catalyst
• Mentor
• Life
• Canvas
• Praxis
• Urban Pulse
• Brand Quest

Our Bureau

Conventional biological treatment techniques have been found to be suitable for continuous operations with constant sewage load. In pilgrim centres sewage generation is seasonal.

Thiruvananthapuram , Sept. 9

MAJOR pilgrim centres such as Sabarimala in Kerala, known for their seasonal festival occasions that draw lakhs of devout people from across the southern States, have always provided a logistical and infrastructural challenge to the best prepared of administrations.

Sewage generation and the concomitant issue of air and water pollution flowing from these short-duration festivals have combined to pose a serious health hazard to members of the public who reside in these areas and depend on a common source of water for drinking and other purposes.

Conventional biological treatment techniques have been found to be suitable only for continuous operations with more or less constant sewage loading. In pilgrim centres, transport stations and holiday/summer resorts, hill stations and picnic spots, sewage generation is mainly seasonal, and that too varies in proportion to floating population.

In these places, the biological treatment systems have often been seen as failing to measure up; chemical precipitation process is the only alternative. Through this technique, the colour and turbidity present in sewage can be removed more or less completely. Along with this, more than 90 per cent of the dissolved organics contributing to biological oxygen demand (BOD) and chemical oxygen demand (COD) also get removed.

In chemical precipitation process, the modular type approach for phase separation equipment is possible so that when sewage load varies widely, the number of modular operations can be varied in proportion to the sewage generation. This adds to its general acceptability for big pilgrim centres such as Sabarimalai and Velankanni, says Mr P. Sivasankara Pillai of the Thrissur-based Envirochem Laboratories. He explained the salient features of the new technique at the just concluded national conference on biological treatment of wastewater and waste air (BTWWA) at the Regional Research Laboratory-Thiruvananthapuram (RRL-T) here.

Depending on the sewage generation, sufficient numbers of sewage collection tanks and sewage treatment modules (STMs) would have to be operated in parallel. The advantage here lies in the fact that the number of STMs to be operated or the duration of operation can be regulated in proportion to the rate of sewage generation on any day.

This flexibility is not at all possible in the case of continuous clariflocculators, in whose case, as the sewage flow becomes low, it will take a few days to get the tank filled up to the overflow launder. The result is that the accumulated mass becomes septic and starts emitting foul-smelling and toxic gases.

Chemical precipitation technique had been the standard process of sewage treatment in the US and European countries from the beginning of the last century. The cost of chemicals (coagulants) and the difficulty of sludge disposal were the main drawbacks seen as prohibiting their use in developing countries. But, now, chemical precipitation has made a comeback with low cost coagulants having been developed from waste materials.

On the other side, advancement of solid-liquid separation techniques has more or less solved the sludge disposal problem, too.

Citing an instance of purifying sewage by chemical precipitation followed by chemical oxidation, Mr Pillai said adequate dosage of an effective coagulant is uniformly mixed with sewage for precipitating and removing suspended and dissolved organic as well as inorganic matter.

Special type of flash mixers, flocculators and phase separation systems are employed for quick processing of sewage.

Article E-Mail :: Comment :: Syndication

Stories in this Section
`Chemical process better bet to treat sewage'

Copyright © 2003, The Hindu Business Line. Republication or redissemination of the contents of this screen are expressly prohibited without the written consent of The Hindu Business Line