Interaction with pathogenic microbes and plant in the domestic sewage: Natural treatment systems
By: Pankaj Kanaujia* and Madhu Prakash Srivastava**
District Jhansi is located in the Bundelkhand region of central India in the South Western part of Uttar Pradesh and lies between longitudes 78˚20’ to 78˚30’ E and latitude 25˚6’ to 25˚29’ N. Jhansi city is situated in a semi arid region of the country. It is located in the plateau of central India, an area dominated by rocky reliefs and minerals underneath the soil. It has an average altitude of 284 meters. Most part of the year the city people experience acute scarcity of water for agricultural, industrial and domestic uses. Water bodies are severely degraded as a result of discharge of raw sewage from communities into its watershed. The consequent consumption of water is making the city people more prone to diseases and health problems. Fresh water bodies are increasingly exposed to high load of nutrients from ever increasing urban population in the city thereby, causing serious impacts on its flora and fauna.
Sewage canals are under tremendous pressure due to ever rising population. The impacts are further aggravated during summer due to excess shortage of water. Treatment of wastewater is required because it causes foul smell, bad odours, and demands for dissolved oxygen in the water bodies, adds nutrients (nitrate and phosphate) and increases suspended solids or sediments in streams. The untreated water also contains pathogenic bacteria.
Moreover, frequent drought situation has severely affected agriculture. Today fresh water bodies are receiving million of liters of wastewater with high concentration plant nutrients and pathogens. Some studies in our laboratory has also revealed that the fresh water bodies in Jhansi city are highly eutrophic as result of input excessive plant nutrients from sewage and agriculture run off. These irresponsible situations exacerbate the quality of the water and limit or even prevent the use of the water for various purposes as they threaten the human health and aquatic life seriously. About 80% of the consumed water is released into local water bodies as wastewater. Wastewater treatment and reuse of treated water are potential solution to address the problem of poor quality and quantity of water in this region.
Pathogenic organisms present in wastewater flourish in the presence of rich nutrient of the domestic waste. In addition, domestic wastewater also contains certain group of bacteria and other microorganisms. The most commonly occurring pathogens in the wastewater include strains of Salmonella, Shigella, Leptospira, intra-pathogenic form of Escherichia coli, Pasteurella, Vibrio, Mycobacterium, human enteric viruses, cysts of Entamoeba histolytica and hookworm larvae. Bacterial pathogens are removed by different processes such as sedimentation, chemical reaction, natural die-off and action of different and biologically active substances released by the plant roots and predation by water animals (zooplanktons).
Although some have documented that macrophytes can improve BOD and bacterial removal from wastewaters through sedimentation, mechanical filtration, nutrient assimilation, oxygenation, and microbial attachment mechanisms, others did not detect any significant difference between planted and unplanted systems. Multifarious treatment technologies are available today to restore and maintain the chemical, physical and biological integrity of the nation's waters. The potential use of a variety of natural biological systems like ponds, land treatment and wetlands systems helps to purify water in a controlled manner. These systems show their efficiency due to their design, performance, operation and maintenance. These systems must be upgraded from time to time to ensure the removal efficiency of the contaminants
However, there is a lack of proper wastewater treatment in India. With respect to environment this situation should be changed as fast as possible. In most Indian cities, there are very few wastewater treatment process and lack of effective environmental pollution laws. Today conventional treatment facilities fail in satisfying all demands of ecologically aware societies. This is because they don’t harmonize with basic principles of water conservation, do not enable reclamation and reuse of water and nutrients, generate toxic sludge as by product and use chemicals harmful to environment and people.
Phytoremediation is the in situ use of plants and their associated microorganisms to degrade contain or render harmless contaminants in soil or groundwater that can be accessed by the roots of plants. Even though the use of plants in remediation of contaminants is not new, phytoremediation has evolved in the past decade as a technology for the treatment of contaminated soil and groundwater offering low costs and less landscape disruption. Constructed wetlands are decentralized, low-energy, low-cost systems to improve water quality. They rely on natural wetland function which includes plants and microorganisms which uptake and breakdown the wastewater nutrients either aerobically or an aerobically. These systems are responsible for providing multiple benefits like improvement in water quality, water security & reuse, CO2 reduction, provides habitat for many plants and animals. It also acts as a source for recreation, education, aesthetic/amenity value. Plants (free- floating, emergent or submerge vegetation) are the part of constructed ecosystem to remediate contaminants from municipal, industrial wastewater, metals, acid mine drainage. Constructed wetlands are used to treat the municipal waste water also eliminate the pathogenic microorganism by macrophytes plant like Typha latifolia, Phragmites karka and Phragmites australis.
A number of problems can be solved by constructed wetland like denitrification, adsorption of ammonia, ions, heavy metals, phosphorus compounds, removal of pathogens, uptake of toxic substances as well as decomposition of biodegradable organic matter and toxic organic compounds.
*Department of Botany, University of Lucknow, Lucknow 226007
**Mamta Girls Degree College, Barabanki