BrownKawa Farmstead is pleased to announce that we have been conditionally approved by the State of New Mexico to install and test an experimental vermifilter septic system on our remote rural property.
Related blog posts:
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Also check out the Worm Septic section of our FAQ
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Some helpful vermiseptic references we used to support our permit:
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1. Sinha et al, Griffith University, Queensland, Australia (2008) Sewage treatment by vermifiltration with synchronous treatment of sludge by earthworms: a low-cost sustainable technology over conventional systems with potential for decentralization. The Environmentalist
This primary research paper is referenced by many other papers on the topic, indicating its wide acceptance. It describes a controlled experiment and discusses the results in a wider environmental and economical context.
Key applicable points: This gives an excellent overview of the many benefits of earthworms as applied to biofiltration of wastewater, detailing the many mechanisms in this odor-free process resulting in clean water disinfected enough for reuse in agriculture, parks, and gardens. The paper notes the lack of sludge using vermifiltration, and quantifies the level of treatment attained. Suspended solids were removed by over 90%, resulting in no sludge. Turbidity was removed by over 98%, pH was almost neutralized, BOD loads were removed by over 98%, and COD was removed by 80-90%, through enzymatic action.
The paper also explains the earthworm life cycle and interaction with its environment, emphasizing that the population can adjust to the variable wastewater environment due to worms’ ecological adaptation abilities.
Aspects not applicable to our design: The researchers also discuss processing of toxic wastes which is far beyond the expectations of our small household septic application, and we do not aim to use the water in agriculture, parks or gardens (other than our drainfield wildlife garden).
2. Arora et al, Indian Institute of Technology, Roorkee, India (2014). Pathogen removal during wastewater treatment by Vermifiltration. Environmental Technology
This primary research paper quantifies pathogen removal from wastewater in a vermifiltration system and explores the mechanisms behind pathogen removal.
Key applicable points: The study found that BOD was reduced by 84.8% and COD was reduced by 73.9%. They go on to quantify the impressive removal rate for various pathogenic indicator organisms, and explored further to identify and analyze antibacterial microorganisms symbiotic with earthworms found within the vermifilter bed. They conclude that vermifiltration removes over 99% of coliforms from wastewater and therefore provides primary, secondary, and tertiary treatment (disinfection) in one.
Aspects not applicable to our design: The experimental treatment bed in this study used almost 50% inorganic filtration materials (gravel and sand) and 50% vermicompost. Our design uses a smaller layer of gravel, and the vermicompost includes a deep layer of organic filtration material such as wood chips. Our system is only aiming for primary treatment at this point, although impressive results like this would certainly not hurt our system.
3. Gupta, ABES Engineering College, Ghaziabad, India (2015). A Review on Effectiveness of Earthworms for Treatment of Wastewater. International Journal of Engineering Development and Research
This paper provides a literature review of several studies from 1991-2014 of vermifiltration of wastewater from various applications.
Key applicable points: Domestic wastewater study showed BOD reduction of 85-93% and COD reduction of 74-80%. A different study on rural domestic waste water showed COD reduction of 81.3%. The paper also gives a succinct overview of earthworm ecology, biology, economic significance, earthworm mechanism in wastewater treatment, and the synergistic action of enzymes, microorganisms, and earthworms, based on the literature review.
Aspects not applicable to our design: The paper also summarizes results in the gelatine industry, palm oil mill effluent, dairy industry, and treatment of sludge, all irrelevant to our household septic system application.
4. Taylor et al, University of Queensland, Australia (2004). Characterizing The Physical And Chemical Properties of a Vermicompost Filter Bed. Compost Science & Utilization
This primary research paper focuses on analyzing the composition and properties of the vermifilter bed.
Key applicable points: The study found that the vermifilter bed naturally develops unique filtration properties such as high wastewater retention time and complex flow characteristics due to the action of earthworms, far greater field capacity than is possible with inorganic filter systems.
Aspects not applicable to our design: The system described diverges from our design in some key ways. The tank is fully submerged underground requiring a wind ventilator, while ours is above ground and vented directly to ambient air. There is no aeration and drainage tube within the vermifilter bed in the Australian tank as there is with ours. The described tank is designed to take all household organic waste including kitchen scraps, newspaper, and cardboard, while ours is designed for household sewage only. The described tank therefore has a buildup of compost and requires an auger to remove compost through the top of the tank (where unprocessed waste is deposited). The system described is commercially available in Australia but not in the United States.
5. Yadav, K.D. et al (2011). Vermicomposting of source-separated human faeces by Eisenia
fetida: effect of stocking density on feed consumption rate, growth characteristics and
vermicompost production. Waste Management.
This abstract simply describes the optimum stocking density of worms for processing wastewater.
Key applicable points: .5 kg is appropriate for bin startup, as the worm population grows rapidly. 3 kg of worms is optimum for full production in processing sewage. In this study the worms ate a maximum of 40-45% of their body weight in human feces per day.
Aspects not applicable to our design: We did not have access to this full article but included it as justification for the .5 kg initial stocking minimum described in our manual (which is also the amount used in Reference 7).
6. “Happy Worms All Winter Long!” article from NM Healthy Soils website.
This article describes how to maintain earthworms through winter. The author, Sam McCarthy, raises earthworms in the Santa Fe, New Mexico area.
Key applicable points: With enough bedding volume, food, and water (conditions similar to our design), the author finds that earthworms maintain their activity throughout the winter.
Aspects not applicable to our design: Our design has additional supports for the worms, since the bin is housed in an insulated shed which would protect it further from the elements (both heat and cold).
7. Vermicomposting Toilets Design and Construction, and Function and Maintenance manuals from http://www.vermicompostingtoilets.net.
Finally, this critical, thoughtfully developed and referenced website provides the open-source design and use documents on which our design is based. Other sections of the website discuss the history and various aspects of vermifiltration. This website is maintained by Wendy Howard, who brought the technology to Portugal and worked for its acceptance by building departments in communities there.
Key applicable points: There are strong parallels between our highly derivative manual and this site’s design and construction and function and maintenance web pages, both of which form the basis for our manual. The whole website provides context for our efforts.
Aspects not applicable to our design: Our document was modified to meet New Mexico requirements and to focus on the combined greywater/blackwater portions of the website, since New Mexico requires our system to handle all of the liquid waste on our site (even though our house is also plumbed for greywater diversion).