Worms evolved to turn plant and animals wastes into soil. After more than 600 million years, they’re perfectly adapted to the task. Aristotle is quoted as saying “Worms are the intestines of the Earth” and it’s not a bad analogy for what they do. Earthworms’ bodies works as ‘biofilters’. They ingest and degrade organic wastes, converting them into nutrient-dense and microbially-rich soil. Their burrows aerate the soil. They lock up heavy metals and organic pollutants within their bodies. They’re able to increase the hydraulic conductivity and natural aeration of soil not just through the physical action of burrowing, but by granulating the clay particles which pass through their bodies.
The life span of an earthworm is about 3–7 years depending upon species and ecological situation. They harbour millions of nitrogen-fixing and decomposer microbes in their guts. They are enormously adaptable to a huge range of environmental conditions. Eisenia foetida, for instance, can tolerate soils nearly half as salty as salt water. They can also tolerate high concentrations of heavy metals and organic pollutants. Eisenia foetida even survived 1.5% crude oil containing several toxic organic pollutants.
Earthworms survive within a temperature range of 5-29°C. Their optimum temperature range is 20–25°C. Moisture levels of 60–75% are ideal, though they can also tolerate extensive water loss by dehydration. Cold is not as big an issue for them as heat – while their activity slows down a lot in winter, excessive heat can kill them instantly.
Vermicomposting ecosystems establish and self-regulate very easily, with worm numbers rapidly adapting to availability of food. Earthworms are bisexual and can double their number at least every 60–70 days. Given a good food supply and optimal moisture and temperature conditions, earthworms can multiply by 28, ie. 256 worms every 6 months from a single individual. The worms also stimulate and accelerate microbial activity in the system by increasing the population of soil microorganisms and improving aeration through their burrowing actions. The number of bacteria and actinomycetes contained in ingested material increase up to 1,000 times while passing through earthworm guts. A population of worms numbering about 15,000 will in turn foster a microbial population of billions of millions.
There are many good fully-referenced studies now available on earthworms’ role in soil creation and waste treatment. Here are a few for further reading …
- Sewage treatment by vermifiltration with synchronous treatment of sludge by earthworms: a low-cost sustainable technology over conventional systems with potential for decentralization. Sinha, R K, Bharambe, G & Chaudhari, U. Environmentalist, December 2008, Volume 28, Issue 4.
- An Overview of the Environmental Applicability of Vermicompost: From Wastewater Treatment to the Development of Sensitive Analytical Methods. Pereira, M G et al. The Scientific World Journal Volume 2014 (2014).
- A Review on Effectiveness of Earthworms for Treatment of Wastewater. Gupta, H. International Journal of Engineering Development and Research, Volume 3, Issue 3 (2015).
- Worming the Way to a Greener Future: Vermicomposting for Municipal Organic Waste Disposal. Katie Kilpatrick. Senior Thesis Environmental Studies, Dr. Liz Gron, Mentor March 15, 2013
- Design and Suitability of Modular Vermifilter for Domestic Sewage Treatment. Bhise H S, Anaokar G S. International Journal of Emerging Engineering Research and Technology, Volume 3, Issue 4, April 2015.
- Vermicomposting of source-separated human faeces by Eisenia fetida: effect of stocking density on feed consumption rate, growth characteristics and vermicompost production. Yadav K D, Tare V, Ahammed M M. Waste Management, Volume 31, Issue 6, June 2011, Pages 1162–1168
- The life-cycle of the compost worm Eisenia fetida (Oligochaeta). Venter, J M & Reinecke, A J. South African Journal of Zoologyy, 23:3, 161-165 (1988)
Worms in sanitation
The flush toilet with centrally-processed sewage treatment has doubtless been a great invention from the human point of view, but it comes at a significant environmental cost. Not only does it pollute enormous volumes of clean water, requiring a lengthy and energy-intensive process to return it to something still short of its original condition, it deprives the soil of an essential component for maintaining its life, health and fertility. The waste of land-dwelling animals, humans included, is not naturally designed to be decomposed in water. Decomposition in water is an anaerobic (without oxygen) process. Anaerobic decomposition is slow, smelly and encourages the growth of pathogens. Treatment of residues is necessary to remove harmful organisms which need never have proliferated in the first place. This process also removes all the beneficial organisms present. This is aside from the heavy metal, pharmaceutical, domestic and industrial chemical pollution present in sewage which is not removed in conventional processing.
The argument against anaerobic processing also applies to septic tanks which, while not requiring the energy inputs that centralised sewage processing does, eventually need to be pumped out because the rate of accumulation of solids generally exceeds the rate of anaerobic decomposition. Water passing through septic tanks is not treated at all. It merely remains in the tank long enough for bulk solids to settle out and scum (oil, grease, fats) to rise to the top. Soil biota in leach fields and soakaways are often insufficient to clean the water of dissolved pollutants and pathogens, leading to nitrate and bacterial pollution of ground and surface waters, especially where conditions are less than ideal (high water table, shallow soils, slopes, degraded soils, soils lacking in organic matter).
In contrast, aerobic decomposition – particularly aerobic decomposition involving worms – is fast, odour-free and pathogen-free. Offensive smells don’t persist in any environment where worms are active. They prevent problems by killing the anaerobes and pathogens which create foul odour. There is no build-up of sludge. Wastes are either completely consumed or converted into rich fertiliser for the soil, full of soil life and nutrients, promoting the growth of healthy vegetation, which in turn nourishes healthy animals and people. Organic and inorganic pollutants are ingested by the worms and locked up in their bodies or otherwise broken down by the microbial flora and fauna present in a vermicomposting ecosystem.
If water is used as a temporary carrier medium for sewage, it’s returned to something much closer to its pristine state after filtration through a vermicomposting ecosystem. Worms degrade the wastewater organics by enzymatic action (enzymes work as biological catalysts bringing pace and rapidity in biochemical reactions). The reduction in the 5-day Biological/Biochemical Oxygen Demand (BOD5), one of the principle measures used in the assessment of successful sewage treatment, is typically over 90% in as short a throughput time as 10 minutes. In 1-2 hours, 98-100% can be removed. Chemical Oxygen Demand (COD) is reduced by 80–90%, total dissolved solids (TDS) by 90–92%, and the total suspended solids (TSS) by 90–95%.
If vermicompost is removed periodically from the system, vermiculture technology gives about 100-1000 times greater value added than other biological technologies.
It’s a no-brainer really. How humanity ever managed to overlook worms’ potential role in either centralised or decentralised sewage processing right from the start is to be wondered at. It’s of little surprise then that people are starting to catch on in a big way now. Many studies have been completed, mostly in India which has been quicker to see the potential in vermicomposting sewage than the West. Many different ways of using worms to process human waste have evolved, from vast worm beds in sewerage works (developed primarily in New Zealand) to high tech domestic scale units.
The biotechnology however, remains embarrassingly simple. It’s possible to install or retrofit a fully-functioning vermicomposting sewage treatment system using little more than materials sourced from industrial waste streams with DIY skills. There is no need for expensive and problem-prone manufactured units. This site exists to encourage the spread of this low tech approach where local permitting allows. In many instances, the regulations governing the use of septic tanks with drainage can cover a vermicomposting system. Speak to your local municipality!
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