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vermicompost effect on pathogens and more

Page history last edited by unityfire888@... 11 years, 7 months ago

 

Below is an excellent research paper I found posted on http://www.ecobaby.ie/composting/vermicompost01.htm

 

Eco Nappies and Vermicomposting    (to go back use your browser's 'back' button ) Updated August 2007

See how some young students won the Intel Environmental Award 

at the 2003 Esat BT Young Scientist and Technology Exhibition at Dublin's RDS.

Click Here for Details: http://www.ecobaby.net/ecobaby_news/news-esat_bt_exhibition01.htm

How can Eco Nappies be Composted?

The most efficient way to compost Eco Nappies is using earthworm composting. You may find this referred to as 'vermicomposting'. With vermicomposting, the worms are very active in their search for suitable food. They rapidly penetrate all parts of the nappy, breaking down the pulp, and excreting the material, making it available for microbes to break down. 

How does earthworm composting work?

Worms feed on organic material, break it down and then excrete it as worm castings or vermicompost. The castings are in the form of tiny pellets which are coated with a gel. This crumb-like structure helps improve soil drainage and aeration. Worms are constantly tunneling which also helps aerate compost and soil and enables water, nutrients and oxygen to filter down. This is also a major factor in the rapid breakdown of the Eco Nappy.

Why is Worm Compost so good for plants?

The organic matter also undergoes chemical changes in the process. This make the nutrients more readily accessible to plant roots but in a form that is slowly released when required by the plants. Vermicomposting has this same effect on toxins, such as heavy metals found in sewage sludge. The process is called 'fixation' and it prevents plants taking up more than they need. Studies also show significant pathogen reduction in organic matter that has been through the vermicomposting process.

The vermicompost acts like a buffer for plants where soil pH levels are too high or low making soil nutrients available again to the plant The castings are much higher in bacteria, organic material and available nitrogen, calcium, magnesium, phosphorus and potassium than soil itself Vermicompost is biologically active and will continue to condition soils for up to 4 years.

Experiments in the US on tomato crops have shown that adding vermicompost will increase production by up to 33%.

Can Earthworm Composting reduce waste volume?

The vermicomposting process also reduces waste volume (up to 60% ) and compacts it giving it higher nutrient intensity and improved water holding capacity. 

Is Vermicomposting popular?

Vermicomposting is set to become increasingly popular in the next century as it yields rich organic fertiliser, recovers energy rich resources, safely disposes of organic waste and helps tackle environmental problems such as landfill and the expense of collecting and transporting this waste. In fact, a number of local authorities in Ireland already promote the use of Vermicomposting.

Is Worm Composting Fast?

Vermicomposting is much faster than regular composting. Compost can be ready in 1 month whereas normally it might take 6 months).

Can you suggest some more advantages to Worm Composting?

  • Some examples: Waste materials, like food scraps or animal manure, are packed with primary nutrients such as energy, proteins and minerals which were originally costly to produce. Vermicomposting this waste converts it into a valuable end product and returns these nutrients to the soil where it can be put to good use once again.

  • In compost application experiments, plots with added worm compost showed almost the same yield as artificially fertilised plots while plots with added organic compost showed much lower yields. Vermicompost also aids soil aeration and drainage so improving soil condition. Vermicompost is valued highly by gardeners.

  • Vermicomposting waste will produce no pollution or unusable residue making it a very effective form of recycling. The organic matter that passes through the digestive tract of the worm is excreted as castings. The by-products of this process are water vapour and carbon dioxide, occurring at the natural rate of organic matter decomposition.

For a sustainable environment, outputs from each production cycle should become inputs to other enterprises as in nature. Vermicomposting is an ideal example, as the worm composting process mimics nature.

Can earthworms deal with toxic substances in the composter?

Some relatively toxic substances can be found in the waste we put into composters. As long as the worm composter is working properly, the worms will be able to handle these substances. Heavy metals become soluble and therefore potentially toxic in acidic environments. Worms prefer a relatively alkaline environment. Normally ground garden limestone is sprinkled into the composter. (Only use garden lime, NOT Quicklime, of course!). Worms carry out fine grinding of the lime particles. This neutralises any excess acidity and liberates plant nutrients stored in the rock. Heavy metals are also fixed in the soil and released slowly avoiding toxicity.

Worms develop and maintain a culture of effective aerobic bacteria by culling pathogens, fungi and anaerobic bacteria. They also ensure the organic mass is well aerated.

How does Worm Composting work?

Vermicomposting is much more complex than worms simply eating and excreting organic material. It is a highly complex chain of chemical, biochemical and biological interactions and reactions. The whole process is based on natural systems which have evolved ov

er hundreds of millions of years. Worms play a vital role in creating the optimum conditions for the beneficial organisms to establish and reproduce. These 'good' organisms compete with and dominate the more harmful microbes. The waste is reduced in volume and increased in nutrient value. 

So who's responsible?

It takes more than just the worms to make vermicompost. The worms eat, chew and churn up the waste. The other organisms which accompany them also break it down. A simplified description of the overall mechanism is described below:

 1.    The worms ingest organic matter, fungi, protozoa, algae, nematodes and bacteria. This is passed through the digestive tract. The majority of the bacteria and organic matter pass through undigested (although the organic matter has been ground into smaller particles). This forms the casting along with metabolite wastes such as ammonium, urea and proteins. The worms also secrete mucus, containing polysaccharides, proteins and other nitrogenous compounds. Through the action of eating food and excreting their casts, worms create “burrows” in the material. This in turn increases the available surface area and allows aeration.

2.    There is an abundance of oxygen and nitrogenous compounds (urea, proteins and NH3) in the excreta (vermicast) and mucus secreted from the external tissues of the worms. Some bacteria require oxygen (aerobic bacteria) whereas some object to oxygen and prefer its absence (anaerobic bacteria). Anaerobic bacteria are responsible for the stench from stagnant drains, refuse sacks and landfill sites. With the aerobic conditions in vermicompost, aerobic microbiological growth increases. It is believed that the initial burst of microbiological activity mainly consists of nitrogen fixing bacteria, nitrification bacteria, and to a lesser extent, aerobic bacteria. This is based upon previously established information that burrow walls have a high proportion of the total nitrogen fixing bacteria and that casts have higher concentrations of soluble salts and greater nitrifying power. Accompanying this microbiological growth is the breakdown of organic nitrogen compounds to ammonia and ammonium.

The good news is that the sweet smelling aerobic process overcomes the ugly smell of anaerobes. That is why worm compost piles (properly fed and maintained) smell so nice!

3.    The whole process consumes organic matter and creates a ruffled surface in the burrow walls. The large surface area and improved aeration results in favourable conditions for obligate aerobes (such as Pseudomonas spp., Zoogloea spp., Micrococcus spp. and Achromobacter spp.). The continued growth of the microbiological population continues to increase the rate of decomposition of the material.

Air flows through the material more readily, minimizing the likelihood of anaerobic biochemical reactions occurring. This minimizes the formation of sulfide and ammonia gasses, odors that are typically present if anaerobic conditions are established. Objectionable odors disappear quickly, due to microorganisms associated with the vermicast

What about dangerous pathogens, enteric viruses and parasites?

Naturally, it is important that where potentially harmful organisms are in materials being composted, they should not be present in harmful numbers when the process is finished. With earthworm composting, this is indeed the case.  

The vermicomposting process has a profound effect on the levels of pathogens namely E.coli, Faecal Coliforms and Salmonella spp. with reductions of >99.9% possible. Material that is Vermicomposted exhibits greater pathogen reduction than that achieved with conventional composting. As all three of these pathogens are not obligate aerobes (that is requiring oxygen to survive, grow and multiply), it is likely that these organisms are subject to exploitative competition. The obligate aerobes namely Pseudomonas spp., Zoogloea spp., Micrococcus spp. and Aebromobacter spp. have evolved to process nutrients and reproduce at the highest efficiency in aerobic conditions and so the pathogens are excluded from nutrients and space as the obligate aerobes continue to increase under ideal conditions. 

A similar reduction in numbers exists for enteric viruses due to the lack of host species, exposure to a microbiologically active environment and the secretion of virucidal enzymes by the earthworms during the digestion process. An identical pattern is observed during the vermicomposting process when examining parasite Helminth ova) numbers, primarily due to the lack of host organisms and possibly direct digestion by the earthworms. 

Benefits of Vermicompost

The typical levels of the nutrients (N, P, K) in vermicomposted green waste are of the order of 1-2 %. It would appear that the vermicompost does not compare favourably with commercial chemical fertilisers however two important factors are overlooked when comparing the two, the microbial content and the organic matter content.

Chemical fertilisers are either sterile or have negligible microbiological activity. The chemical fertilisers are composed primarily of water-soluble chemical salts and as such organic material rarely forms part of chemical fertilisers. Once the salts have been depleted from a chemical fertiliser, then re-application is required to maintain the nutrient levels. The presence of nitrifying and nitrogen fixing bacteria in vermicompost means that nitrogen can be fixed from the atmosphere and converted to plant soluble nitrates.

The process continues as long as there is sufficient organic matter (which is present in vermicompost) and so re-application is not required at the same rate as chemical fertilisers. The ability of the microbiologically active vermicompost to regenerate the nutrients from the atmosphere, organic matter and water replaces those lost from chemical fertilisers by leaching, plant uptake and chemical reactions. In relation to moisture holding capacity and improvement of soil structure, chemical fertilisers have negligible effect, as they primarily consist of water-soluble salts. Vermicompost, on the other hand, due to the aggregate nature of the worm castings has appreciable water holding capacity and its use leads to improved soil structure. 

Vermicompost requires no curing (as traditional composted materials do) as it is already populated with beneficial microorganisms The overall time required (and hence the cost) for processing is therefore greatly reduced, and the process produces no toxic by-products or waste. The vermicompost itself is highly valued by gardeners all over the world and has a significant market value.

 

Find this scientific paper (excerpt below) at

http://www.oardc.ohio-state.edu/michel/csu.pdf

Compost Science & Utilization, (2001), Vol. 9, No. 1, 38-49

The Effectiveness of Vermiculture in Human Pathogen

Reduction for USEPA Biosolids Stabilization

Bruce R. Eastman1, Philip N. Kane2, Clive A. Edwards3, Linda Trytek4,

Bintoro Gunadi3, Andrea L. Stermer1and Jacquelyn R. Mobley 1

1. Orange County Environmental Protection Division, Orlando, Florida

2. Florida Department of Environmental Protection, Orlando, Florida

3. Soil Ecology Laboratory, Ohio State University, Columbus, Ohio

4. Tri-Tech Laboratories, Inc., Orlando, Florida

A field experiment tested the feasibility of vermicomposting as a method for elimi-

nating human pathogens to obtain United States Environmental Protection Agency

(USEPA) Class A stabilization in domestic wastewater residuals (biosolids). The ex-

perimental site was at the City of Ocoee’s Wastewater Treatment Facility in Ocoee,

Florida, and Class B biosolids were used as the earthworm substrate. Two windrows

of biosolids 6 m long were heavily inoculated with four human-pathogen indicators,

fecal coliforms, Salmonella spp., enteric viruses and helminth ova. The test row was

seeded with earthworms, Eisenia fetida. The quantity of E. fetidawas calculated at a

1:1.5 wet weight earthworm biomass to biosolids ratio and the earthworms allowed

time to consume the biosolids and stabilize the biosolids. The test indicated that all of

the pathogen indicators in the test row were decreased more than in the control row

within 144 hours. The test row samples showed a 6.4-log reduction in fecal coliforms

compared with the control row, which only had a 1.6-log reduction. The test row sam-

ples showed an 8.6-log reduction in Salmonella spp., while the control row had a 4.9-

log reduction. The test row samples showed a 4.6-log reduction in enteric viruses

while the control only had a 1.8-log reduction. The test row samples had a 1.9-log re-

duction in helminth ova while the control row only had a 0.6-log reduction. Dr. Jim

Smith, Senior Environmental Engineer and Pathogen Equivalency Commission

(PEC) Chair, for the USEPA, indicated by personal communications, that a three- to

four-fold reduction in indicator organisms would be sufficient to warrant serious con-

sideration of vermicomposting as an effective stabilization methodology (Smith

1997). These results in conjunction with pilot project results strongly indicate that ver-

micomposting could be used as an alternative method for Class A biosolids stabi-

lization. This was obtained statistically by vermicomposting.

 

 

Achieving Pathogen Stabilization Using Vermicomposting

After two years of tests, a project in Florida finds that vermicomposting is effective in reducing pathogen levels in biosolids to meet Class A requirements.

By: Bruce R. Eastman

Reprinted with permission from BioCycle November 1999, pages 62-64

Within the last decade, implementation of state and federal regulations and other local codes have changed biosolids processing in Florida. Previously, biosolids stabilization varied greatly among the state's 3,500 to 4,000 wastewater treatment facilities. Public and privately owned wastewater treatment facilities were required to stabilize their biosolids to a minimum Class C standard for land application, with most facilities using aerobic or anaerobic digestion. Requirements for septage solids stabilization, prior to publication of the current rules and regulations, were minimal at best. While record keeping was more organized than for septage stabilization, it was still insufficient.

With implementation of the new rules, these facilities were required to stabilize to a Class B standard. Class C was no longer satisfactory for land application. For most small facilities, this was impossible to achieve without prohibitive retrofitting and expansion, as they usually generated Class C biosolids.

Consequently, it became incumbent upon government to explore alternative methods. The Orange County (Florida) Environmental Protection Division (OCEPD) undertook research for the potential use of earthworms as an alternative human-pathogen (pathogen) stabilization method for biosolids. Research revealed studies suggesting that vermicomposting may be effective in stabilizing pathogens. In some cases, precomposting of biosolids was done to eliminate pathogens. OCEPD staff felt, however, that the earthworms would eliminate pathogens during the vermicomposting process, making the precomposting step unnecessary. Thus the "non-thermal windrow vermicomposting" method was developed.

In 1995, a partnership was formed between OCEPD, American Earthworm Com-pany and the city of Ocoee, Florida. The goal was to develop a Class A pathogen reduction method that is both cost-effective and meets all criteria for public health and safety set forth by the governing agencies. However, the U.S. Environmental Protection Agency (EPA) had not established standards in this area. After communicating the goals of the project and its potential benefits, the EPA developed criteria by which this project and future research could be applied to public health and safety.

Initially, a pilot study was conducted to evaluate vermiculture's effectiveness with biosolids on a small scale. The pilot study demonstrated a noticeable reduction in the four pathogen indicators: fecal coliform, Salmonella sp., enteric virus and helminth ova in the biosolids. The next step was to begin a full-scale operation to define the project's operational feasibility. The EPA issued a two-year experimental permit in March, 1997, with project oversight for EPA performed by the Florida Department of Environmental Protection (DEP). Standard operating procedures would be developed from the information gathered throughout the full-scale operation.

FULL-SCALE DEMONSTRATION

In order for vermicomposting to be considered by the EPA as an alternative methodology for Class A pathogen stabilization, the project needed to demonstrate a three-to four-fold reduction of pathogen indicators that had been spiked into the biosolids in the test and control plots. The EPA office in Cincinnati set those parameters using the reasoning that if vermiculture can demonstrate a three- to four-fold reduction in residuals that have abnormally high number of pathogen indicators, than it could be assumed that it would reduce pathogen content to the requirements of Part 503 in residuals containing normal numbers of pathogens. (EPA's Class A pathogen reduction requirement is as follows: The density of fecal coliform in the biosolids must be less than 1,000 most probable numbers (MPN)/gram total solids (dry-weight basis) or the density of Salmonella sp. bacteria in the biosolids must be less than three MPN/four grams of total solids (dry weight-basis)).

To test whether the three-to four-fold re-duction could be accomplished, a portion of the full-scale operation was utilized to house the experimental plots. A structure was constructed to protect these plots from adverse weather. Biosolids (15 to 20 percent solids) were land applied into two rows approximately six m long by 1.5 m wide by 20 cm deep, utilizing approximately 1,361 kg of biosolids each. One row was designated the test and the second was the control. These two rows were inoculated with a minimum 10 to the 5th spike of three of the four pathogen indicators: fecal coliform, Salmonella sp. and enteric virus.

The test row was then seeded with E. foetida at a 1:1.5 earthworm biomass to biosolids ratio. This ratio represented the earthworms' feeding rate for a 24-hour pe-riod. Earthworms were provided 1,361 kg of biosolids for a 14-day feeding period. Samples of both rows were collected from random locations and analyzed throughout the project.

The helminth ova portion of the experimental project was conducted at a separate time due to difficulty in acquiring the helminth ova eggs. Biosolids (15 to 20 per-cent solids) were land applied into two rows approximately 2.3 m long by 1.5 m wide by 23 cm deep. One row was designated as the test and the other the control. The test row was then seeded with E. foeti-da similar to the three pathogen tests. Florida peat, the substrate in which the earthworms were held, was spread across the test row, adding approximately 15 cm to the depth. Earthworms were provided 531 kg of biosolids for feeding for a seven-day period. Samples of both rows were randomly collected and analyzed throughout the project.

ACHIEVING REQUIRED REDUCTION

Analytical results showed that all of the pathogen indicators in the test row had a greater reduction than in the control row. EPA's required three- to four-fold re-duction was achieved in all of the pathogen indicators within 144 hours. Fecal coliform, Salmonella sp. and enteric virus achieved the EPA goal in 24 hours, 72 hours and 72 hours, respectively. The helminth ova achieved this goal within 144 hours. The helminth ova reduction times were slightly elevated compared to the previous test with the three pathogen indicators. OCEPD staff felt this occurred because of the addition of peat (substrate in which the earthworms were held) when the earthworms were added. The earthworms remained in the peat and did not immediately migrate to the biosolids. Therefore, slower reductions may have occurred because the earthworms already had a food source in the peat.

The initial baseline analysis for fecal coliforms in the test row was an average 8.5 billion MPN/one gram; the control row average was 8.3 billion MPN/one g. After just 24 hours, the test row samples showed an average six-fold reduction (98.70 percent) of fecal coliforms; the control row samples had a less than one-fold average reduction (20 percent). Samples collected every 24 hours for 14 days showed that reductions continued in both the test and control rows. However, the reductions in the test row were much greater and quicker than those of the control. This is due to the vermicomposting process, whereas reductions in the control row can be attributed to the natural die-off of the organisms. This is true for all of the pathogen indicators in the control row.

The initial baseline analysis for Salmonella sp. in the test row was an average 4.6 billion cells/25 ml; the control row average was 5.2 billion cells/25 ml. Samples for the Salmonella sp. analysis were collected at 72 hours and 144 hours. After 72 hours, the test row samples showed an average 13-fold reduction (99.99 percent); the control samples showed an average three-fold reduction (93.18 percent).

The initial baseline analysis for enteric virus in the test row was an average 197,000 plaque forming units (PFU)/four grams; the control row average was 173,000 PFU/four g. Samples collected for enteric virus analysis were collected at 72 hours and 144 hours. After 72 hours, the test row samples showed an average six-fold reduction (98.92 percent); the control row only had an average one-fold reduction (53.8 percent).

Viability tests done by a research team at Tulane University (headed by Dr. Robert Reimers) indicated that the helminth ova spike in the test row was 826,000 viable eggs (Ascaris sp.); the control row spike was 841,000 viable eggs (Ascaris sp.). Sam-ples collected for helminth ova analysis were collected at 72 hours and 144 hours. After 72 hours the test row samples showed a less than one-fold average reduction (47.5 percent); the control row samples showed no reduction. After 144 hours, the test row samples showed an average six-fold reduction (98.87 percent); the control row samples showed a one-fold reduction (74.24 percent).

These results show that EPA's required pathogen reduction in the indicator organisms was obtained, suggesting that vermicomposting can be used as an alternative method for stabilization of Class A biosolids. After pathogen stabilization has been achieved, the castings would need to be air dried to 75 percent solids to meet vector attraction reduction requirements. Drying can be done by windrowing or through a mechanical process. The latter takes one to two days (or less); however, caution should be used to prevent the destruction of the beneficial bacteria developed during vermicomposting.

All supporting documentation from this project will be submitted to the U.S. EPA for consideration as an alternative "Class A Pathogen Stabilization Methodology."

Bruce R. Eastman is Assistant Manager with the Orange County Environmental Protection Division, Florida.

November 1999 BIOCYCLE pages 62-64

 

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