Mechanism of Earthworms in wastewater treatment

 

Water, as we all know, is a terrible thing to waste. But for businesses that go through a lot of water—dairy farmers, wineries and sewage plants—vast quantities of wastewater is an unfortunate by-product. Earthworms promote the growth of beneficial decomposer bacteria in waste water & acts as an aerator, grinder, crusher, chemical degrader & biological stimulator. The 2 processes, that is microbial process & vermin process simultaneously work in the vermi-filtration system. Earthworm body works as a biofilter which widens the microbial metabolism by increasing their population. It also grinds, aerate, crush, degrade the chemicals and act as biological stimulator. Microbial and Vermi processes will simultaneously work by treating the wastewater using earthworms. Effluent resulted will be extremely rich in nutrition and can be reused as earthworms are versatile waste water eaters and decomposers. Earthworms have over 600 million years of experience as “ecosystem engineers”. Vermiculture scientists all over the world knew about the role of earthworms as waste managers, as soil managers & fertility improvers and plant growth promoters for a long time. But nowadays they are used in waste water treatment and contaminated soil remediation. About 4,400 different species of earthworms have been identified, and quite a few of them are versatile waste water eaters and bio-degraders and several of them are bio-accumulators & bio-transformers of toxic chemicals.

Ecology of Earthworms

 Earthworms can also tolerate toxic chemicals in the environment. As worms breathe through their skin proper ventilation of air in soil medium is necessary. They can tolerate a temperature range between 50 and 290 C. A temperature of (200–250)C and moisture of 60–75% are optimum for best worm function. Generally, earthworms can also tolerate extensive water loss by dehydration. Earthworms are bisexual animals and multiply very rapidly. After copulation each worm ejects lemon-shaped ‘cocoon’ where sperms enter to fertilize the eggs. Studies indicate that they double their number at least every 60–70 days. Given the optimal conditions of moisture, temperature, and feeding materials earthworms can multiply by 28, i.e. 256worms every 6 months from a single individual. The total life cycle of the worms is about 220 days. Red worms take only 4–6 weeks to become sexually mature. They have been reported to bio-accumulate them in their tissues and either biodegrade or bio transform them into harmless products with the aid often enzymes. They have also been reported to host microbes in their gut which can biodegrade chemicals.

Mechanism of Earthworms in wastewater treatment

 Earthworms are versatile waste eaters and decomposers. It promotes the growth of beneficial decomposer bacteria in waste water and acts as an aerator, grinder, crusher, chemical degrades and a biological stimulator. The two processes-microbial processes and vermin-process simultaneously work in the Vermifiltration system. Earthworms further stimulate and accelerate microbial activity by increasing the population of soil microorganisms and also through improving aeration by burrowing action. Earthworms host millions of decomposer microbes in their gut and excreta called vermicast. The nutrients N and P are further used by the microbes for multiplication and enhanced action. Studies show that the number of bacteria and actinomycetes contained in the ingested material increased up to 1000-fold while passing through the gut. A population of worms numbering about 15000 will in turn fosters a microbial population of billions of millions.

Synergistic action of Enzymes, Micro-Organisms and Earthworms in Vermi-filtration

The role of different types of enzymes, microorganisms, and earthworms for effluent treatments has been studied. Scientists like carried out extensive studies on celluloses from L. rubellus. Their studies confirmed that enzymes can act on specific recalcitrant pollutants to remove them by precipitation or transformation to other products. They can also change the characteristics of a given effluent to render it more amenable to treatment or aid in converting effluent material to value added products.

They also carried studies on the bio management of dairy effluents using an        L. rubellus  culture and concluded that sludge cake could support the growth of earthworms without processing. They also studied about the bio management of paper mill sludge using vermiculture biotechnology.  L .rubellus  was used to treat approximately 1.5 tones of the sludge coming out of the mill daily. The sludge was successfully converted into biofertilizer and plant tonics. The research study later analysed the use of Aspergillus Niger  as an efficient means of protein waste bio conversion while working on waste water from olive mill. It was demonstrated, the utility of fungal species via A. flavus and A. Niger  in the treatment of pharmaceutical waste. It was also reported about bio- management of liquid effluents discharged after secondary treatment from the gelatin manufacturing industry using combination of A. flavus  and A. Niger.    

Economic Significance of Earthworms

Earthworms can physically handle most organic waste water and potentially at a fraction of the cost of conventional methods of wastewater treatment. Vermiculture technology by earthworms is a self-promoted, self-regulated, self-improved, self-driven, self-powered and self-enhanced, very low energy and less chemical requiring zero waste technology, easy to construct, operate and maintain. Any vermiculture technology involves about 100-1000 times higher ‘value addition’ than other biological technologies. It has less operational cost since it requires energy only for pumping of waste and no skilled labour. Maintenance cost is also minimal as it does not involve any mechanical devices.

Importance of  Earthworms in Vitrification 

Organic matter degraded by microorganisms was further digested by colonies of earthworms living in bedding material. Various actinomycetes inhabiting the earthworm’s guts also triggered degradation of solid contents. Studies reported an intensified bacterial diversity in the waste water due to the presence of earthworms (Eisenia fetida), especially in response to nutrients in their casts. Earthworms and microorganisms cooperate in Vermi-Filter ingests and biodegrade organic wastes and other contaminants in waste water. This extends the food chain in normal bioprocesses and thus greatly improves sewage treatment efficiency. Earthworms increase the hydraulic conductivity and natural aeration by granulating clay particles. They also grind silt and sand particles, increasing the total surface area, which enhances the ability to adsorb organic and inorganic matters from waste water. Intensification of soil processes and aeration by earthworms enable the stabilization of soil and the filtration system to become effective and smaller in size. The researcher observed that the presence of earthworms in effluent led to significant stabilization of sludge by enhancing the reduction of volatile suspended solids. Specially, earthworms on the waste water were capable of transforming insoluble organic materials into a soluble form and then, select digesting the sludge particles to finer states, which facilitates degradation of organic material by the microorganisms in the reactor. The studies concluded that ammonia had very low toxicity on the survival of earthworms in the waste water. In this study there were no observation and adverse effects of the selected effluents on the earthworm population.

Potential application of Earthworms in Wastewater treatment

Long-term researches into vermiculture have indicated that the Tiger Worm (Eisenia fetida), Red Tiger Worm (E. andrei), the Indian Blue Worm (Perionyx excavatus), the African Night Crawler (Eudrilus euginae), and the Red Worm (Lumbricus rubellus) are best suited for Vermi-treatment of a variety of solid and liquid organic wastes under all climatic conditions. Researchers have done many experiments into the field of waste water treatment technologies and found that E.fetida  earthworms are effective for treatment of waste water and have sufficiently treated wastewater from different industries.

What makes worms so good at filtering wastewater

Worms in and of themselves are not great at filtering wastewater. Rather, worms target the solids (or TSS) and break this waste down in their stomachs. Their excrement (worm castings) are rich in microbial activity.

This bacterium is aerobic, or needs air to function, and the burrowing earthworms create air channels throughout the system thereby bringing air to these tiny soldiers and creating an optimum living environment. This symbiotic relationship between worms and bacteria is what powers the process, as the bacteria target the BOD of wastewater, the worms target the TSS and nitrogen.Ultimately, BIDA System (Process of BioFiltro company) converts wastewater into a reusable asset and contaminants into nutritious fertilizer onsite.