Removal of Pathogens during Vermi-Stabilization

Properties of Vermicomposts Derived from Cameroon Sheep Dung

Due to a need for sustainability in agriculture, waste products ought to be utilized in the most appropriate way. A study was undertaken relating to the vermicomposting of Cameroon sheep dung (CSD) by the earthworm Dendrobaena veneta. Processing of this waste was investigated using unadulterated CSD and in a 1:1 mixture with unpalatable (waste) hay (CSDH). Results demonstrated that these materials were actively processed by D. veneta with vermicomposts obtained which can be characterized by a higher amount of total nitrogen, phosphorus and potassium (average, respectively, 17.0, 10.5, 13.2 g kg−1 d.m.), as well as lower total carbon and magnesium content (respectively, 340 and 3.2 g kg−1 d.m.), compared with the initial waste material. No significant differences were found between CSD and CSDH vermicomposts with respect to chemistry. Levels of selected trace elements (average: Cu 17.5–18.8, Cr 5.7–5.8, Pb 13.5–14.4, Ni < 3, Cd < 0.4 mg kg−1 d.m.) in both vermicomposts did not exclude their application to agricultural soil as a fertilizer.

A Comprehensive Review of the Fate of Pathogens during Vermicomposting of Organic Wastes

Management of both municipal and industrial organic wastes remains a major threat to biota and the environment due to the presence of pathogens in abundance. Vermicomposting employing earthworms is increasingly gaining attention as a sustainable and ecofriendly technique to transform and sanitize a variety of organic wastes into nutrient-rich biofertilizer. Although considerable research has been undertaken to show that vermicomposting can significantly reduce pathogenic contents, there is little effort to summarize the various mechanisms responsible for it. With the aim to assess the fate of pathogens during vermicomposting of various organic wastes, this article provides a comprehensive summary on the occurrence of pathogens in a variety of wastes vis-à-vis pathogens standards, the efficacy of the process for pathogen reduction, and current knowledge of the plausible mechanisms involved. It is evident from the present study that earthworms and endosymbiotic microbes during vermicomposting tend to eliminate pathogens by enhancing enzymatic activities in both gut- and cast-associated processes. Pathogen reduction during vermicomposting can be plausibly attributed to direct actions like microbial inhibition due to intestinal enzymatic action, and secretion of coelomic fluids with antibacterial properties, as well as indirect actions like stimulation of endemic microbes leading to competition and antagonism, and aeration by burrowing activity. Further, the pathogen reduction during vermicomposting is largely selective, and earthworms exert a differential effect according to the earthworm species and whether the pathogen considered is Gram-positive or -negative, owing to its cell wall composition. However, further research is necessary to understand the exact mechanisms involved for pathogen reduction during vermistabilization of municipal and industrial organic wastes.

Inactivation of bacterial pathogenic load in compost against vermicompost of organic solid waste aiming to achieve sanitation goals: A review

Waste management strategies for organic residues, such as composting and vermicomposting, have been implemented in some developed and developing countries to solve the problem of organic solid waste (OSW). Yet, these biological treatment technologies do not always result in good quality compost or vermicompost with regards to sanitation capacity owing to the presence of bacterial pathogenic substances in objectionable concentrations. The presence of pathogens in soil conditioners poses a potential health hazard and their occurrence is of particular significance in composts and/or vermicomposts produced from organic materials. Past and present researches demonstrated a high-degree of agreement that various pathogens survive after the composting of certain OSW but whether similar changes in bacterial pathogenic loads arise during vermitechnology has not been thoroughly elucidated. This review garners information regarding the status of various pathogenic bacteria which survived or diffused after the composting process compared to the status of these pathogens after the vermicomposting of OSW with the aim of achieving sanitation goals. This work is also indispensable for the specification of compost quality guidelines concerning pathogen loads which would be specific to treatment technology. It was hypothesized that vermicomposting process for OSW can be efficacious in sustaining the existence of pathogenic organisms most specifically; human pathogens under safety levels. In summary, earthworms can be regarded as a way of obliterating pathogenic bacteria from OSW in a manner equivalent to earthworm gut transit mechanism which classifies vermicomposting as a promising sanitation technique in comparison to composting processes.

Comparison of vermicompost characteristics produced from sewage sludge of wood and paper industry and household solid wastes

BACKGROUND

The aim of this study was to determine the potential of produced compost from the sludge of wastewater treatment plant using earthworms and compare it with the vermicompost produced from household solid waste.

METHODS

In the current study, three treatments with the same conditions in terms of organic wastes type were prepared to produce vermicompost from household solid waste and sewage sludges using earthworms. The standard methods were used to determine the physical and chemical parameters in the different produced vermicomposts.

RESULTS

The mean of C/N in the household solid waste, raw biological and chemical sludges was 32, 22.5, and 26.5, respectively. These levels were 16.5, 14.5, and 15 in the vermicomposts. The mean of nitrogen and phosphorus percentages in the vermicompost of solid waste, biological and chemical sludges was 2.2%, 2.6%, 2.3% and 0.72%, 0.54%, and 0.56%, respectively. The mean percentages of organic matters in the initial substrates and vermicomposts of solid waste, biological and chemical sludges were 97.2%, 90%, 80.5% and 65.8%, 67.8% and 63% respectively. The concentrations of heavy metals decreased in all vermicomposts. The EC levels in solid waste, biological and chemical sludges were 1459, 1041, and 1487 μs/cm, respectively. These levels were 544, 385 and 635 μs/cm in the produced compost.

CONCLUSION

Eisenia fetida can convert household solid waste, and biological and chemical sludges produced from wastewater treatment plant into a high-quality and acceptable compost.

A metagenomic analysis displays the diverse microbial community of a vermicomposting system in Uganda

Background

Vermicomposting is a mesophilic process using earthworms to efficiently and at low cost process large volumes of organic waste. It has been suggested to not only increase soil fertility but also increase biomass of beneficial bacteria while reducing harmful bacteria. The aim of this study was to set up a strategy to investigate and characterise the viral as well as the bacterial composition of a vermicomposting system.

Material and methods

The vermicomposting unit used in this study was placed at the Makerere University Agricultural Research Institute Kabanyolo on the outskirts of Kampala, Uganda, and was fed with 80% cattle manure and 20% food waste. On Day 172, the compost was terminated and compost samples were collected from three layers of the unit: the top, the middle and the bottom layer. A metagenomic approach was then applied to characterise the viral and bacterial composition of the vermicomposting system.

Results and discussion

A high abundance and diversity of bacteria were identified. Proteobacteria was the largest phyla in the compost (mainly Alpha-, Gamma- and Betaproteobacteria), constituting almost 65% of the bacterial reads in the data sets. DNA samples from several possible pathogenic bacteria, such as Salmonella spp., Escherichia coli, Enterobacter spp., Enterococcus spp. and Clostridium spp, were detected in the vermicompost, suggesting that there might still be harmful bacteria in the vermicast. Phages constituted the main viral group; apart from phages, mainly insect viruses were identified. The only animal or human virus identified was kobuvirus. In summary, metagenomic analysis was shown to be an efficient technology to characterise the microbial composition of vermicast. The data from this study contribute to a better understanding of the microbes present in this kind of composting system and can help determine measures necessary for safe manure handling.

Vermicomposting as manure management strategy for urban small-holder animal farms - Kampala case study

Inadequate organic waste management can contribute to the spread of diseases and have negative impacts on the environment. Vermicomposting organic waste could have dual beneficial effects by generating an economically viable animal feed protein in the form of worm biomass, while alleviating the negative effects of poor organic waste management. In this study, a low-maintenance vermicomposting system was evaluated as manure and food waste management system for small-holder farmers. A vermicomposting system using the earthworm species Eudrilus eugeniae and treating cow manure and food waste was set up in Kampala, Uganda, and monitored for 172days. The material degradation and protein production rates were evaluated after 63days and at the end of the experiment. The material reduction was 45.9% and the waste-to-biomass conversion rate was 3.5% in the vermicomposting process on a total solids basis. A possible increase in the conversion rate could be achieved by increasing the frequency of worm harvesting. Vermicomposting was found to be a viable manure management method in small-scale urban animal agriculture; the return of investment was calculated to be 280% for treating the manure of a 450kg cow. The vermicompost was not sanitised, although hygiene quality could be improved by introducing a post-stabilisation step in which no fresh material is added. The value of the animal feed protein generated in the process can act as an incentive to improve current manure management strategies.

Hygienic quality of faeces treated in urine diverting vermicomposting toilets

On-site sanitation solutions have gained much interest in recent years. One such solution is the urine diverting vermicomposting toilet (UDVT). This study evaluated the hygienic quality of the composted material in six UDVTs in operation in France. Samples were taken from three sampling positions in each toilet, with increasing distance from the fresh material. The concentration of Salmonella spp., Enterococcus spp., thermotolarent coliforms and coliphages were analysed and plotted against a number of variables. The variables found to have the greatest impact was the pH (for Enterococcus spp. and thermotolarent coliforms (TTC)) and time since last maintenance (coliphages). The pH was found to correlate with the material maturity. The current practise of maintenance can cause recontamination of the stabilised material and increase the risk of regrowth of pathogenic microorganisms. A modification in the maintenance procedure, in which a fourth maturation point is introduced, would eliminate this risk. UDVTs were found to be a good on-site sanitation option as the maintenance requirement is small and the system effectively reduced odour and concentration of pathogen and indicator organisms in human waste while keeping the accumulation of material down to a minimum. If the vermicompost is to be used for crops consumed raw, an additional sanitisation step is recommended.

Vermicomposting toilets, an alternative to latrine style microbial composting toilets, prove far superior in mass reduction, pathogen destruction, compost quality, and operational cost

Composting toilets aim to recycle excrement into safe, stable humus. Preceding this, low costs, low risks, and mass reduction should be ensured. Source separating vermicomposting toilets (SSVCs) outperformed mixed latrine microbial composting toilets (MLMCs) in all categories. MLMCs: incurred ten times greater operational costs; created 10x more operator exposure; employed no proven pathogen reduction mechanism since solid end-products averaged 71,000±230,000CFU/g (fecal-origin) Escherichia coli and 24±5% total solids, consistently failed NSF/ANSI Standard 41; failed to reduce volatile solids compared to raw fecal matter; increased total contaminated dry mass by 274%, and produced alkaline end-product (8.0±0.7) high in toxic free ammonia (Solvita® 2.6±1.5). SSVCs have low maintenance costs and risks; adequate worm density for pathogen destruction (0.03±0.04g-worm/g-material); reduced E. coli 200±244CFU/g in neutral (7.4±0.3), stable (60±10% volatile solids), and mature (4±0 Solvita® NH(3)) end-product.