Author – Punnyatoya Dash
Wastewater management from domestic and industrial sewage is becoming a challenge in developing countries like India. Domestic sewage contains biodegradable organic matter and can be degraded by microorganisms. However, Industrial sewage harbors chemicals and toxic heavy metals. The conventional method of wastewater treatment uses activated sludge, but there are several drawbacks associated with it. These sewage treatment plants not only require a large area but also have low efficiency. They have high energy requirements which also makes them expensive to operate.
To solve the wastewater crisis in India, many scientists have come up with an innovative process of using bio-remediation properties of water hyacinth for wastewater treatment. This process is called ‘Phytoremediation’, which has made wastewater management very much eco-friendly and cost-effective.
The principle behind Phytoremediation
The concept of using a plant-based or a microbiological system to eliminate contaminants had been around for a while, but was not applied to wastewater management till now. An important step in phyto-remediation is choosing an efficient and easily available aquatic plant, where the ability of the plant to thrive in polluted water is crucial. The plant should be able to absorb both organic and inorganic contaminants thus clearing the water.
Water hyacinth (Eichhornia crassipes) is commonly known as an invasive weed that floats on all water bodies, but its high reproductive potential is a boon for phyto-remedial processes. Being a vascular plant with perennial growth, hyacinth is an apt choice for phytoremediation. This macrophyte thrives well in polluted water that has high COD (chemical oxygen demand) and high chlorine levels. Its root system is capable of absorbing toxic and heavy metal pollutants like lead, magnesium and strontium-90. Moreover, its roots harbor aerobic bacteria that further aid in removing impurities from the wastewater.
This eco-friendly wastewater treatment process can be sustained in all types of climatic conditions, be it tropical, wet or dry. However, it is important to note than phytoremediation with water hyacinth has its own limitations. The optimum temperature for hyacinth growth is from 28-34°C with a pH range of 4-10. Changes in the temperature or pH of the water can thwart the growth of this aquatic plant.
Commercial implementation of Phytoremediation using Water hyacinth
SHEFROL in Puducherry
Professor Rajendra B. Magar, Afroz N. Khan and Abdulrazzak Honnutagi from Kalsekar Technical Campus in Maharashtra realized that an eco-friendly wastewater management system was the need of the hour. Professor Rajendra B. Magar and his team applied this phytoremediation concept in Puducherry in a small-scale implementation, which has gained economic acceptance. The village of Chinna Kalapet in Puducherry has encamped this system of eco-friendly wastewater treatment. They used water hyacinth and four-leaf clovers to make treatment more efficient. This process was named SHEFROL which stands for sheet flow root level. In this system, wastewater passes down through thin sheets and comes in contact with the roots of aquatic plants. These plants absorb pollutants, and hence detoxify the water. The intensive water root microorganisms help reduce turbidity from the wastewater. Furthermore, the topography of the village contributes to the easy distribution of wastewater leading to an odor-free wastewater management system!
Sukinda Chromite mines in Odisha
The concentration of chromium in wastewater in water bodies around Sukinda Chromite mines in Odisha increased causing a threat to the biotic community. Moreover, chromium-6 is a hazardous pollutant that can cause kidney disorders, cancers and various biotic disturbances. Water hyacinth came to the rescue at Sukinda Chromite mines to remove hexavalent chromium by the phytoremediation process! The plant was powdered and mixed with wastewater. The powder attaches to the chromium particles and settles them down. The water, with a significantly lesser concentration of chromium can be then decanted from the top. 0.4g of water hyacinth powder can purify a liter of wastewater in 30 minutes while live water hyacinth can remove 99.5% chromium-6 from wastewater in 15 days! Apart from clearing chromium toxicity, this method of phytoremediation also reduces the level of total dissolved solids, biological oxygen demand and chemical oxygen demand. The major advantage of this system is its consistency in the long run.
Alappuzha’s wastewater management in Kerala
Sewage wastewater created problems of wastewater management in the Alappuzha district of Kerala. Canals and lagoons were filled with wastewater and a lot of problems were being created by this. A sustainable and cost-effective solution was needed. Nagpur based CSIR – National Environmental Engineering Research Institute (NEERI), came up with an improved version of phytoremediation called ‘Phytroid technology’. A few advantages of this system are its low energy requirements, cost-effectiveness and negligible maintenance.
Biogas production from Hyacinth in Andhra Pradesh
M.S Shivakiran, Manikanta and Ravichandra, three biotechnologists from Vignan University in Guntur district of Andhra Pradesh have developed a model for conversion of domestic sewage water into biogas by using water hyacinth. They have employed a method called ‘Phytoremediation’ through which aquatic plants like water hyacinth could be used to produce biogas. The Vignan University team experimented by setting up a trench of 2,000-liter capacity in which water hyacinth is cultivated. The plant biomass is harvested and chopped in an organic waste converter to make it convenient for digestion of biomass in the biogas plant. A biogas plant in the university now produces 200 liters of gas daily; enough to run a canteen. The biogas produced is being supplied to the hostels in the university campus and the bio-manure is being utilized in the herbal garden.
As more and more people realize the benefits of phytoremediation with water hyacinth, this system is bound to find its way into many more commercial applications across India.