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Process | October 2011

The latest trends in waste water treatment

Some of them are fixed film, geotextile filtration, membrane filtration, UV oxidation process and bio block, says Dr Abhay Kumar.

Due to the high population and the scarcity of land filling areas, municipalities face a major challenge in collecting, recycling, treating and disposing of waste material.Proper recycling of wastewater will reduce the health risk to humans and animals and also avoid contamination of surface and ground water.

There is a need for good waste water treatment processes and water management since the world is  currently on the brink of water scarcity. To avoid such a scenario, wastewater treatment and water management awareness among the masses is vital. In view of current emerging issues, past approaches to control water pollution have been modified by adopting new technologies.

Issues with Current Treatment

•Generates a large amount of sludge that must be sent to the offsite for disposal and handling the sludge is a difficult task.
•Most of the treatment is not effective in some seasons.
•High energy requirement.
•High operation and maintenance requirement.

In case of small community systems, waste water treatment seems more important. In the early ages, people used well water for drinking and other purposes but the increase in population led to the need for new technologies for waste water treatment and its reuse. Advanced treatment process can be an extension of conventional processes and improvement upon earlier drawbacks. It gives us a hope that better quality waste water increases the scope for its reuse.

New technologies for small communities includes fixed film package treatment systems, geotextile filtration, membrane filtration, UV oxidation process and bio block. Other methods which indirectly help in wastewater treatment are drip irrigation, evapotranspiration and mound systems. All these systems have been fine-tuned to meet the current problem.

Fixed Film Systems (FFS)
A biological process that  employs a medium such as rock, plastic wood or other natural or synthetic solid material that will support biomass on its surface and within its porous structure. The main applications are that they reduce the biochemical oxygen demand (BOD) and total suspended solids (TSS) from septic tank effluents to meet higher effluent
standards.
 
Geotextile filtration
Geotextile membranes are poly propylene or polyester or from natural fibres like coir and can be used in waste water treatment. These membranes make it amenable for use in flowing water where micro organisms and other contaminants can get attached to the geotextile fibres.  

UV oxidation Process
By using UV oxidation, the water quality can increase and also help reduce the carbon footprint. Powdered activated carbon (PAC), which was used earlier, could remove the odour and taste but could not remove the MIB (2-methylisoborneol)  and geosmin sufficiently.

A comparative study was done to replace the PAC, in which it revealed that a PAC dosage of
30 mg/l reduced 55 percent of geosmin concentration. Meanwhile, the UV oxidation system exhibited an 80 per cent reduction in the peak flow and 90 per cent reduction in the average flow.

Bio Block
This process is also called a 'Biological urinal block'. It is biodegradable and safe to use. It removes the cause of odour and prevents the blocking of traps and pipes. The concept behind this is using beneficial organisms which are non-pathogenic. The microbes digest the organic urinal crystals rapidly and allow the free flow of drainage lines.

Poo Gloos
It is an igloo-shaped device that is used to clean wastewater with bacteria. It is six feet in diameter, three feet high and has a foot tall base. It is made in such a way that seven plastic domes will be lined with biofilm to maximise the surface area. The device can be installed in existing wastewater treatment lagoons that need to be treated. Tubes within each device pump air bubbles to support the autotrops. This circulates the sewage that can then be fed to the bacteria.

Deployable Aqueous Aerobic Bioreactor (DAAB)
DAAB is a new finding developed by the Texas Research Institute for Environmental Studies (TRIES) at Sam Houston State University (SHSU), and PCD works. This technology offers a low-cost and highly transportable method for wastewater clean up. The advantage of this technique is to convert wasterwater to Environmental Protection Agency (EPA) acceptable standards.

This process uses specially selected bacteria to clean wastewater by removing organic and inorganic material. This system is completely autonomous and can be monitored, diagnosed and controlled via the internet.

Solar Detoxification
In recent years, it has been found that solar detoxification plays a major role in disinfecting water. The actual process behind this is that waste water collected from bathrooms and kitchens can be stored in the settling tank for primary treatment and passed onto the second tank where it will be mixed with titanium dioxide, which can then be pumped to the solar flat plate.  

Membrane Bioreactor
Membrane bioreactors (MBRs) are increasingly being specified as the best available technology for all wastewater treatment applications. This process is a combination of ultra filtration and biological treatment. This replaces the traditional clarification process in the activated sludge process. According to Daigger 2003 and Judd 2006, submerged MBRs have proven to be more cost and energy efficient than tubular side stream modules.

The most serious problem with this system is membrane fouling as a result of deposition of biosolids, colloidal species and scalants on the membrane surface resulting in flux and permeability decline.

The basic need for a waste water process is to speed up the natural process by which water purifies itself. In ancient periods there was no need for water treatment due to a natural process that eliminated contamination. But the increased population and emerging industries have increased the need for treatment processes. As the economy grows, there is demand for upgraded water treatment systems. The character and quantity of contaminants presenting problems today are far more complex than those in the past. In future, more improved technologies will be introduced to overcome waste water treatment process drawbacks.
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