Reeds to the rescue
the Punjab government has introduced reed-bed system ( rbs ), an ecofriendly way of treating sewage with the help of reed plants in Roorki village of Fatehgarh Sahib district. T he system is a specially engineered simulation of a natural wetland ecosystem for the treatment of sewage, sullage and industrial effluent with the help of microbes in the roots of reed species, which are special plants acclimatised to survive in harsh polluted environment. The whole system, based on root zone technology is environment friendly and does not require any chemicals, pesticides or electricity and skilled operators. It requires minimum maintenance, produces no sludge, aesthetically looks good (like a garden), and lasts for 25-30 years.
T he system consists of a sedimentation tank, a reed bed where reed is planted, and an outlet for treated water. The polluted water flows into the sedimentation tank, where the suspended solid particles settle down. The water then flows into the reed bed where it comes in contact with the roots of the reed. The roots have rhizomes and other bacteria in it, which help in the break down of organic solids. More than 3,000 types of bacteria and tens of thousands of fungi thrive in the bed.
During respiration, the atmospheric oxygen is taken in by the reed which passes through its leaves, stem to the roots. The oxygen is then released from the roots to get into the surrounding bed where the aerobic microbes survive. Away from the aerobic (oxygen containing) zone, oxygen starts depleting and here the facultative microbes thrive. Further away is the anaerobic zone (oxygen free) where anaerobic microbes thrive. These microbes oxidise the impurities in the wastewater, and decompose the contaminants to their basic forms. Reed plants consume the broken contaminants as staple diet. Thus, there exists a symbiotic relationship between the microbes in the reed bed and the reed species.
The water treated here is let out into a nearby pond for uses like irrigation, animal bathing, groundwater recharge, pisciculture, and other such activities. It is not safe for drinking, but if further treated, can be used for drinking purposes as well.
Reed-bed system is successful in treating water containing various contaminants, such as ammonia, heavy metals, suspended solids, phenols, pesticides, textile dyes, faecal coliforms, etc. It drastically reduces the biological oxygen demand ( bod ) and chemical oxygen demand ( cod ) of the water. " T he system is successful in dealing with not only the household sewage, but also industrial effluents. We have set up the largest rbs for industrial effluent treatment (40,000 litres per day (lpd) at l & t John Deere, near Pune. We have reed bed system in our Ankleshwar factory as well,' says Arvind Kulkarni, manager, Wastewater Management, Ion Exchange (India) Ltd.
Apart from the treated water, at the end of the cycle, the reed is cut and used as biomass (compost).
According to Ashok Olla of Delhi branch of Ion Exchange, on an average treating 1,000 lpd of sullage approximately requires 10 sq m of area and costs about Rs 25,000. As the area increases, the cost decreases. So it is financially viable to set up large reed bed systems, he adds.
N Vasudevan of Centre for Environmental Studies, Chennai maintained that rbs is quite suitable to semi-urban and rural areas. "We are quite satisfied with the treatment of sewage but not satisfied with the industrial effluents. Mainly the microbes present at the rhizosphere region of the reed plant plays a role in the conservation of the organics in the wastewater,' he added.
In Australia, reed-bed systems are used for stormwater runoff and sewage treatment. It is being successfully used for a number of years in various European countries, notably Germany and Holland. Many Canadian communities use rbs to treat sludge and transform it into relatively clean water and humus. Worldwide innovations are happening in the field of rbs . North Lincolnshire Council has developed an innovative smallscale portable system for industries generating small quantities of liquid effluent. As against horizontal reed bed, vertical system require less space and are equally efficient.
Reed-bed system in Roorki Roorki is a small village of about 1,000 households, situated 40 km away from Chandigarh. The Punjab government has hired Ion Exchange (India) Ltd on a one-year contract to set up the rbs in Roorki and show its viability. The state government will carry out the civil engineering works, like desilting of the pond.
Earlier, the area of Roorki pond was 1.6-2 hectares (ha), now it is reduced to 0.8 ha due to siltation and encroachments. "For the past 40-50 years, desiltation has not taken place. People no more need sand/mud for building their kuccha houses as they have pucca houses. Also the village has got piped water supply, thus wastewater is aplenty. Our aim is to desilt ponds so that groundwater is recharged and activities such as pisciculture thrive,' says J S Kesar, financial commissioner, department of rural development and panchayats , Chandigarh.
"Out of the 0.8 ha pond area, rbs will cover an area of 750 sq m. The depth of the system would be 8-10 m with an average of three to four reed plants planted per sq m. In all, 75,000 litres of sullage will flow in the system, with an output of 60,000 litres a day. Rest being consumed by the reed and some evaporation losses,' informs Kulkarni.
According to Kesar, the total cost of Roorki rbs is about Rs 4-5 lakh. Funds for the project are being generated from various resources and routed through the panchayat . Gram panchayat is contributing about Rs 1.5 lakh. For the setting up of the system, Ion Exchange is charging Rs 2.85 lakh.
On paper, the Roorki rbs project looks flawless, but problems exist at the field level. When this reporter visited the site, desilting of the pond was moving at a snail's pace. No sincere efforts were made to remove encroachments from the pond area. Although, Kesar recently maintained that disilting work is complete and rbs would start functioning soon.