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Krishnasamy, K., Nair, J. and Hughes, R.J. (2013) Vermifiltration systems for liquid waste management: a review. International

Journal of Environment and Waste Management, 12 (4). p. 382-396.

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http://dx.doi.org/10.1504/IJEWM.2013.056908

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Int. J. Environment and Waste Management, Vol. x, No. x, xxxx 1

Copyright © 20xx Inderscience Enterprises Ltd.

Vermifi ltration systems for liquid waste management: a review

Karthika Krishnasamy*, Jaya Nair and Robert James HughesSchool of Environmental Science,Murdoch University, South Street,Murdoch, Western Australia 6150, AustraliaE-mail: [email protected]: [email protected]: [email protected]*Corresponding author

Abstract: Vermifi ltration is an innovative wastewater treatment process that implies the use of composting worms to treat water loaded with organic contaminants. It is considered to be an innovative technology that provides a sustainable solution for the treatment of wastewater with synchronous sludge reduction and treatment. In this paper, an overview of vermifi ltration systems in liquid waste management is presented. The paper starts by giving an overview of the vermifi ltration process and then provides details of current studies and technologies used to treat wastewater using the vermifi ltration process. The anti-clogging nature of vermifi ltration systems is compared with other biological treatment systems and the key factors infl uencing the process and the treatment effi ciency of the process are critically reviewed. The scope and improvements to the process are fi nally suggested.

Keywords: onsite and decentralised wastewater systems; vermifi ltration; vermifi ltration systems; wastewater treatment.

Reference to this paper should be made as follows: Krishnasamy, K., Nair, J. and Hughes, R.J. (xxxx) ‘Vermifi ltration systems for liquid waste management: a review’, Int. J. Environment and Waste Management, Vol. x, No. x, pp.xxx–xxx.

Biographical notes: Karthika has a B.Sc (Hons) in environmental science from Murdoch University, Western Australia. She is interested in developing cost-effective, sustainable waste management techniques. Her research was based on treating solid and liquid anaerobic wastes using composting worms. Karthika is currently doing her PhD at Murdoch University focusing on saline soils of Western Australia.

Dr Nair currently an adjunct senior Lecturer at Murdoch University, Western Australia is also Director of RAUM International Pty ltd involved in solid waste management. Having PhD degrees in aquatic biology and in Environmental Science she has worked on various projects related to water and waste for over 20 years. Dr Nair has been teaching and supervising undergraduate and post graduate students on Pollution management mainly on water and waste treatment and has published book chapters, in international journals and presented the work widely in international conferences.

Robert has a PhD in environmental science from Murdoch University. He has approximately 30 publications in wastewater treatment, solid waste management

IJEWM 13(1) 08 Krishnasamy et al. (3)_r(R1).indd 1IJEWM 13(1) 08 Krishnasamy et al. (3)_r(R1).indd 1 6/8/2012 1:33:40 PM6/8/2012 1:33:40 PM

2 K. Krishnasamy et al.

and ecological risk assessment and worked for several years as a researcher at the Environmental Technology Centre. He has taught at Murdoch University in environmental: engineering, science, management and policy. Robert has worked with 4 government departments in Australia. Recently he was involved with the review of works approvals for wastewater treatment plants, solid waste facilities and infrastructure associated with mining and oil and gas facilities. He is currently reviewing environmental impact assessments on mining proposals.

1 Introduction

Wastewater is generated from a variety of sources, such as households, food processing industries, farms and others. The high volume of wastewater produced from these sources has ensured that wastewater treatment is required to reduce the impacts of wastewater disposal on receding environments and the benefi cial uses of these environments, e.g., potable, irrigation, recreation or industrial water use (Hughes et al., 2006). However, to meet appropriate disposal guidelines, there is a constant need for the development of cost effective and environmentally sound wastewater treatment systems. This is especially important for developing countries and rural communities, where there may be less subsidisation of wastewater treatment system development and increased per capita development, maintenance and operational costs. For rural communities and developing countries, decentralised treatment systems offer an advantage in treating and disposing of the wastewater without the need for deep sewerage; they can be developed gradually, reducing the upfront capital costs and increasing the possibility of community ownership through community development projects, e.g., condominium sewerage systems.

The use of composting worms in solid waste management has been widely studied by various researchers on a range of organic wastes and it is known as vermicomposting (Dominguez, 2004) or vermistabilisation (Loehr et al., 1988). The application of composting worms in wastewater management is termed vermifi ltration or lumbrifi ltration or vermicompost fi ltration (Hughes et al., 2006). Vermifi ltration is a new technology based on the science of vermicomposting and wastewater treatment through bio-fi ltration and attached growth systems. Research on the use of composting worms in liquid waste management has gained importance after they were successfully used in wet composting toilets (Smith and Hughes, 2004). The reason vermifi ltration has gained importance with researchers is because it represents a novel technology that is environmentally friendly, easy to manage and not energy or capital-intensive (Hughes et al., 2006). This paper describes how composting worms can be used in liquid waste management based on an overview of the studies on vermifi ltration. The term ‘worms’ will be used for ‘composting worms’ throughout this paper.

2 The vermifi ltration process

Vermifi ltration and vermicomposting are natural methods of organic waste management that rely on the use of worms (Bajsa et al., 2004). The main difference between the two processes is that vermifi ltration systems treat liquid and solid wastes (Taylor et al., 2003), whereas vermicomposting systems mainly treat solid wastes. In a typical vermifi ltration system, there


Vermifiltration systems for liquid waste management 3

will be a few sections (beds), one or two upper beds where solid wastes are retained and biodegraded through conventional vermicomposting and lower beds where the liquid wastes are biodegraded, commonly using attached bio-fi lm growth (Hughes et al., 2009). The organic solids that are fi ltered out of the incoming wastewater in the upper beds are biodegraded using worms and associated micro-organisms (Hawkins et al., 2008) and form a layer of humus material rich in organic matter (Hughes et al., 2008). The production of humus in the system increases the porosity and hydraulic conductivity of the upper beds (Taylor et al., 2004) and the high surface area of the particles that make up the humus, leads to greater adsorption of contaminants (e.g., nutrients, surfactants, metals) (Hughes et al., 2009). The use of worms to produce the humus helps to overcome clogging and cake formation and reduces the solid fraction by up to 60%. It also reduces maintenance requirements (Sinha et al., 2008).

The action of worms on the wastes creates air spaces through movement and turning of the substrate, producing aerobic conditions in the humus, with oxygen available to aerobic decomposer microbes, accelerating the biological decomposition of the wastes (Loehr et al., 1985). Aerobic processes are faster than anaerobic processes when biodegrading organic matter (Pell and Nyberg, 1989). The increased oxygenation of the humus leads to greater oxygen exchange with the wastewater fl owing through the upper vermifi ltration beds, which leads to greater chemical oxygen demand (COD) removal from the system (Hughes et al., 2008; Taylor et al., 2004). The oxygenation of the incoming wastewater also increases nitrifi cation in the system (Hughes et al., 2008).

2.1 Comparison of vermifi ltration with other biological wastewater treatment technologies

The vermifi ltration system offers a number of advantages when compared with other commonly used biological wastewater treatment systems. According to Yang et al. (2008), the vermifi ltration system was convenient to operate when compared to conventional activated sludge treatment methods, as there is no sludge formation with the vermifi ltration system. Moreover, the removal of total nitrogen and total phosphorus was reported to be 10% higher in vermifi lters compared to activated sludge systems; there is also three times more NH4–N removal in vermifi lters (Li et al., 2009).

Vermifi ltration overcomes the limitation of aeration and clogging that occurs in constructed wetland systems and reed beds. Chiarawatchai et al. (2009) investigated the potential of worms in reducing the clogging of constructed wetlands receiving high strength swine wastewater. It was found that worms translocated the clogging solids from the pores of the gravel as castings to the surface. The presence of worms in the non-clogged reed bed was also revealed by Davison et al. (2005). Researchers claim that once a reed bed gets established and reaches maturity, worms will appear and transport solids, which in turn prevent clogging of the reed beds pores (Lismore city council Report, 2009). Sinha et al. (2008) argue that there is a low utilisation of waste materials in wetland-based treatment systems compared to vermifi ltration, but there is no detailed study to prove this comparison.

Healthy soil acts as an effective bio–geological fi ltration medium adsorbing organics, inorganics, pathogens and parasites, with most of the removal occurring in the top 12–15 cm (Monk, 1995). In any fi ltration system, the hydraulic conductivity of the infi ltrative surface is predominant in achieving effective treatment (Hawkins et al., 2008). Though there is a signifi cant removal of Biological Oxygen Demand (BOD), COD and suspended solids by the soil fi lter (Spyridakis and Welch, 1977), the system may fail due to the formation of sludge and fi lms of



micro-organisms that grow under conditions of excess carbonaceous nutrients as slime capsules (Tyler et al., 1977), creating a ‘clogging zone’ that can reduce the hydraulic conductivity of the fi ltration medium (Otis, 1985; US EPA, 2002). Thus, the overall treatment effi ciency of soil fi ltration is decreased. The worms are the vital macerator organisms in vermifi ltration systems and they constantly devour the colonies of micro-organisms. The worms also improve the adsorption properties of the geological system by grinding them in their gizzard (Sinha et al., 2008) and also enhance the biological decomposition of waste. The pores created by worms have a signifi cant impact on wastewater treatment. The infi ltration rate can be 4–10 times greater in soils with worms compared to those without worms (Edwards and Bohlen, 1996) and does not require back washing, e.g., back washing is required in sand fi lters, to clean the clogged pores.

2.2 Key factors in the vermifi ltration processThere are a number of factors that will impact on the performance of a vermifi ltration system. The key factors are worm species and biomass, hydraulic retention time, hydraulic conductivity, constituents and characteristics of the wastewater. They are reviewed below.

2.2.1 Worm species and biomassDifferent worm species have different burrowing characteristics and therefore, have different impacts on the treatment process. The anecic earthworm species make permanent vertical burrows into the deep layers, acting as preferential fl ow paths that may reduce the treatment effi ciency due to lessening of contact of the effl uent with the fi lter matrix. On the other hand, endogeic worms make extensive non-permanent horizontal burrows that may enhance wastewater treatment by distributing the effl uent over a larger area (Hawkins et al., 2008). The third category are epigeic worm species like E. fetida and E. Andrei, critical for biodegradation of wastewater solids because they like organic rich substrates compared to the other species (Hughes et al., 2007). Due to their preference for organic rich substrates like manure, epigeic species are most commonly used to inoculate systems and ensure that a suitable humus fi lter is produced (Klein et al., 2005).

The population density, maturity and health of the worms in the vermifi ltration bed infl uence the treatment process. The optimum worm density is one of the important parameters for effi cient functioning of a vermifi ltration system (Li et al., 2008). The treatment effi ciency of vermifi ltration is positively affected by the number of worms per unit area in the vermifi lter bed. A vermifi ltration system should be started with enough worms to vermicompost the incoming wastes and produce a suitable humus fi lter. It has been estimated that a relatively high number of at least 15,000–20,000 worms/m3 of the vermifi ltration system should be used (Sinha et al., 2008).

Recent research is beginning to show that perhaps the number of worms to inoculate a system may not be highly critical in systems treating low strength wastewater, as the worm population can adjust itself according to the incoming waste in a vermifi ltration system. For example, vermifi ltration studies on wastewater treatment by Li et al. (2009) that began the treatment with a population of 3,000/m2 built up to 12,000/m2 at the end of the study. It should be noted, however, that as with typical vermicomposting, if the waste entering the vermifi ltration system has high organic matter content and a volume greater than the worms can readily biodegrade, or if the worms are unable to build a population within a short time period, then the system may fail. For instance, it is known in vermicomposting research that if the worm biomass is too low in the vermicomposting system, the decaying organic matter usually lies as a thick mat on the surface (Edwards and Bohlen, 1996). In a



vermifi ltration system, this thick mat of untreated waste can lead to poor treatment of the incoming wastewater, as the thick mat typically has a low hydraulic conductivity and ability to adsorb and transform incoming contaminants. In many cases, this thick mat will create an anaerobic condition in the system, killing the worms which diffuse oxygen through their bodies and leading to a collapse of the treatment process.

2.2.2 Hydraulic Retention TimeHydraulic Retention or Residence Time (HRT) is the average time the wastewater remains in the vermifi ltration treatment system. HRD is an important factor in the treatment, where the worms and other profi le materials convert and stabilise the nutrients, BOD, COD and suspended materials in the wastewater. However, most of the solids and some nutrients will be in the system for much longer and the worms biodegrade them. The treatment effi ciency of the system increases with HRT. The residence time might increase due to the accumulation of casts in the system over time (Taylor et al., 2003), arising from an increase in the vermifi lter volume. The HRT of a vermifi ltration system can be calculated as (Sinha et al., 2008):

( )( )

( )3

3

Hydraulic retention time h

porosity of the medium volume of the soil profile m

flow rate of wastewater through the vermifilter media m / h

=

×

The optimal HRT of a vermifi ltration system can be determined based on the concentration of the organic pollutants in the wastewater. The system removed high BOD loads of 10,000–1,000,000 mg/L from food processing industry wastewater within 4–10 hours of HRT (Sinha et al., 2008b). The most appropriate HRT for optimal removal of BOD, COD, TDSS and turbidity of brewery wastewater with 500 worms in about 0.032 cum was found to be between 3–4 hours (Sinha et al., 2008b) while that of dairy wastewater was found to be from 6–10 hours (Sinha et al., 2007). The worms can reduce the small BOD loadings of sewage (200–400 mg/L) within 30–40 minutes and high BOD sewage water in 1–2 hours (Sinha et al., 2008). However, in some cases, the optimal HRT ranged from six to nine hours for sewage wastewater (Xing et al., 2005). Due to the differences of HRT between some studies, it is important to consider that the optimal HRT may vary with the vermifi ltration system design.

2.2.3 Hydraulic Loading RateThe Hydraulic Loading Rate (HLR) is defi ned as the rate at which wastewater enters the vermifi ltration system. HLR depends on several factors like structure, bulk density, effl uent quality, profi le aeration and method of effl uent application (Eliasson, 2002). In a vermifi ltration system, HLR is the volume of wastewater that can be treated reasonably in a given time. Hydraulic loading rate of the vermifi ltration system can be calculated as (Sinha et al., 2008):

( )( )

( )

3

2

Hydraulic loading rate h

volumetric flow of the wastewater m

area of the profile (m ) time taken by the wastewater to flow through profile h

=

×



Similar to soil based treatment systems, a high HLR can reduce the HRT of the system and therefore, the treatment’s effi ciency (Sinha et al., 2008). This is mainly because wastewater requires a certain contact time with the humus and attached growth in vermifi ltration to allow for the adsorption of contaminants, transformation of nitrogen and reduction of COD (Hughes et al., 2006).

There has been a range of HLR in experimental studies. For example, the HLR ranged from 2.0–3.0 m3/m2/day for the pilot study by Xing et al. (2005) and from 0.5–1 m3/m2/day in the study by Yang et al. (2008), while raw wastewater from a household was applied at the rate of 0.13 m3/m2/day in a study by Taylor et al. (2004). In an innovative study to treat rural sewage continuously, Li et al. (2009) started the fi ltration with 0.2 m3/m2/day and gradually increased it to 1.3–1.5 m3/m2/day and even up to 4 m3/m2/day. They observed that when HLR exceeded 3 m3/m2/day, some worms escaped from the vermifi lter. Hence, the application was maintained at 1.5–2 m3/m2/day and increased to 3 m3/m2/day during the summer months to cool the fi ltration system (Li et al., 2009). However, an application of 1 m3/m2/day was considered to be the best to get more effi cient and stable treatment (Li et al., 2009).

2.2.4 WastewaterThe pH of the wastewater infl uences the survival and activity of worms. Vermifi ltration systems have been found to stabilise the acidic or basic wastewater (Hughes et al., 2007). In a study by Hughes et al. (2007), it was also found that the earthworm species E. fetida and E. andrei, can survive pH values between 6.2 and 9.7, with juvenile impairment at both higher and lower pH levels.

Wastewater composition may signifi cantly affect the earthworm population and can limit the treatment process (Hughes et al., 2007). The toxicity of various components and their threshold limits has not been widely studied. In an attempt to overcome this knowledge gap, Hughes et al. (2008; 2009) studied the concentration of ammonium and sodium salts that limit the performance of a vermifi ltration system. The studies found that sodium chloride is one of the more toxic of the common ionic sodium compounds in wastewater. The studies also found that ammonia and common sodium salts pose a low toxicity risk to a vermifi ltration system from normal household use.

Redox potential of the wastewater is also critical in the vermifi ltration system (Philippe et al., 2006). It should remain positive to maintain the population of worms, as worms cannot survive in conditions with low availability of oxygen for a long period of time (Edwards and Arancon, 2004). Due to this, the continuous sprinkling of highly reduced water should be avoided for effi cient working of the system (Li et al., 2008). Further research needs to be conducted in this area, by focusing on the relationship between worm submersion in a low dissolved oxygen environment and vermifi ltration system health.

2.3 Vermifi ltration system designThe systems used by various researchers have varied in their design and profi le construction. In most of the cases, the set up included plastic tubing, sand, gravel and wood chips to achieve effi cient treatment. The systems were designed either to recharge the groundwater with wastewater through in situ treatment or constructed to recover treated water for further usage (Bhawalkar, 1995).

One of the earliest systems used to recharge groundwater (Fig. 1a) or recover the treated water (Fig. 1b) was described by Bhawalkar (1995). In case of in situ treatment for recharging



groundwater, the worms grind the soil, thereby increasing the hydraulic conductivity and surface area that can adsorb the organics and inorganics in the wastewater. The wastewater gets more refi ned as it further passes through the soil matrix. The loading rate of sewage water was maintained at 2 m3/m2. In case of water recovery design as illustrated in Figure 1b, the wastewater can be treated in single or multiple stages based on the concentration of wastewater (Bhawalkar, 1995).

The schematic representation of a system designed by Li et al. (2008) to treat swine facility wastewater is presented in Figure 2a. In this system, the medium used was wood chips and vermicastings (humus) over which the wastewater was sprinkled. The surface was made into ridges and furrows so the worms can occupy the ridges if there was poor drainage. The treated water was then recycled back into the swine facility (Fig. 2b).

The dowmus wet composting system to treat solid and liquid waste is illustrated in Figure 3. This system can be used to treat toilet and kitchen wastes/black and grey water effectively for a household. The solid wastes are vermicomposted and removed as they accumulate on the top. The liquid gets treated in the fi lter bed and the treated water is mixed with rain water to improve the quality for irrigation.

The system designed by Mobbs for sustainable houses is space effective, with a three layer fi lter system (Mobbs, 1998). A system designed to treat vegetable wastes along with wastewater is illustrated in Figure 4.

Figure 1 (a) Vermifi ltration system to recharge groundwater (Bhawalkar, 1995) and (b) Vermifi ltration system to recover water for reuse (Bhawalkar, 1995)



Biolytix Filter™, considered to be the fi rst widely used commercial vermifi ltration system in Australia (Taylor et al., 2003), consists of an aerobic fi lter bed with worms and beetles to convert sewage into humus (Fig. 5). The bottom layer constitutes an 80 micron geofabric layer to remove fi ne particles and the treated water is used for irrigation (Biolytix, 2003).

In a study made to compare the effect of a ceramic fi lter with sand in vermifi lters (Fig. 6), Yang and Zhao (Yang and Zhao, 2008) designed a duel system with both ceramic and sand media. The system with the ceramic fi lter had higher treatment effi ciency in terms of BOD, COD and ammonia removal when compared to the sand. Moreover, there was more air circulation and only slight abrasion to the surface of worms in the ceramic fi lter, compared to a sand in fi lter matrix (Yang and Zhao, 2008).

2.4 Treatment of wastewater from various sourcesThere are a few reported studies on the treatment of wastewater using vermifi ltration. Li et al. (2008) investigated the methodology for swine wastewater treatment by vermifi ltration.

Figure 2 (a) Vermifi ltration of piggery effl uent (Li et al., 2008) and (b) Schematic representation of experimental design used in piggery farm (Li et al., 2008)



Gardner et al. (1997) and Yang et al. (2008) investigated the method to treat on-site effl uents from rural settlements. There was also a facility set up to treat the organically loaded water in a community of 2,000 inhabitants in France (LIFE, 2005).

The potential to treat domestic wastewater using vermifi lter beds was also investigated in a few researches (Bajsa et al., 2004; Chaudhari, 2006; Sinha et al., 2008; Taylor et al., 2003; Xing et al., 2005), while positive results were obtained for wastewater treatment from dairy and brewery industries (Sinha et al., 2007; Sinha et al., 2008b).

2.4.1 Removal of organics (BOD and COD) The removal of BOD and suspended solids is commonly high in vermifi ltration systems (Table 1), largely due to their ability to fi lter out solids and produce humus. The more

Figure 3 Schematic representation of dowmus vermifi ltration system (Bajsa et al., 2004)

Figure 4 Cross-section of vermifi ltration system (Mobbs, 1998)



Figure 5 Biolytix wastewater treatment system (Biolytix, 2003) (see online version for colours)

Figure 6 Comparison study of sand and ceramic pellet as fi lter media (Yang and Zhao, 2008)

Table 1 Biological Oxygen Demand (BOD5), Chemical Oxygen Demand (COD) and Suspended Solids (SS) removal (%) from various vermifi ltration studies

Source Wastewater source BOD5 COD SS

Xing et al. (2005) Sewage 91–98 81–86 97–98Chaudhari (2006) Municipal 98–100 45 –Sinha et al. (2007) Dairy industry 98 80-90 90–95Yang et al. (2008) Wastewater treatment

plant86 72 88.5

Sinha et al. (2008b) Domestic 90 80–90 90–95Sinha et al. (2008b) Brewery 99 71 95–98LIFE (2005) Domestic 97 75 94Li et al. (2009) Sewage 89.3 83.5 89.1



insoluble the matters, such as suspended solids in wastewater, the more easily they are removed by vermifi ltration systems. Suspended solids such as faecal matter and other readily biodegradable organic matter are trapped at the top of the vermifi ltration bed and then processed by worms and microbes.

In suitably designed vermifi ltration systems, such as those which provide suitable areas for conversion of liquid COD, COD removal is also high. The reason liquid COD removal is greater in some systems was tested by Taylor et al. (2003) in the performance of small-scale vermifi lter beds loaded with raw domestic wastewater along with paper wastes and kitchen scraps. They evaluated COD and BOD values of water from varying fi lter depths. It was found during the study that soluble organic compounds from the humus and raw waste in the top of the system leached through to lower sections where it was biodegraded. Hence, it appears a vermifi ltration system will require a suitable fl ow path and residence time.

The other critical factor for COD consumption is the availability of oxygen. In the column mesocosm studied by Taylor et al. (2003) to treat wastewater, oxygen content increased up to 82% compared to the infl uent, which had only 6% dissolved oxygen. Li et al. (2009) recorded outfl ow dissolved oxygen values above 9 mg/L after treatment through a vermifi ltration system.

2.4.2 NutrientsNutrient removal has been observed by a number of authors in vermifi ltration systems (Hughes et al., 2008; Li et al., 2008; Taylor et al., 2003). Ammonia has been found to be removed through two key processes. For example, Li et al. (2008) found that up to 60% of the ammonia in wastewater was removed through adsorption on organic matter and woodchips. Li et al. (2008) did also note some minor volatile emissions of ammonia. The studies by Taylor et al. (2003) and Li et al.(2008) found that the majority of ammonia was converted to nitrate via nitrifi cation or after adsorption. Nitrifi cation in vermifi ltration systems can be attributed to the movement of the worms which aerate the humus at the top of the system, leading to an exchange of oxygen into the incoming wastewater. The humus is aerated through the creation of burrows and the production of small aggregate vermicasts, which have a high affi nity for oxygen exchange with the atmosphere (Parkin and Berry, 1994).

Denitrifi cation of nitrate has also been found to occur in vermifi ltration systems (Taylor et al., 2003). Taylor et al. (2003) suggested that there are small pockets of anaerobic conditions within a vermifi ltration system, where denitrifi cation takes place. Due to the occurrence of nitrifi cation and denitrifi cation in vermifi ltration systems, the total nitrogen concentration of wastewater is reduced (Li et al., 2009). The removal of nitrogen is typically dependent on the residence time and fl ow path in the vermifi ltration system (Taylor et al., 2003).

The level of phosphorus removal in vermifi ltration systems has been found to vary signifi cantly between systems. This is mainly because phosphorus is removed principally through adsorption in vermifi ltration systems and those systems without media which can adsorb phosphorus have low phosphorus removal rates. For example, the column mesocosm designed by Taylor et al. (2003) had very low to no phosphorus removal. This system did not have a suitable amount of humus or media which could adsorb phosphorus and relied mainly on phosphorus uptake by worms and associated micro-organisms as the principal removal mechanisms. In another system designed by Li et al. (2008), there was approximately 30% phosphorus removal, mainly because the system had woodchips and humus which could adsorb the phosphorus. Li et al. (2008) found in the study that there was an accumulation



of phosphorus in the system; they also noted that there was an accumulation of potassium and over 50% reduction of organic matter in the system, which may indicate that the humus and woodchips in the system are a stable and suitable medium for recycling trace metals and nutrients present in wastewater back into agriculture.

2.5 Seasonal fl uctuations and the system performanceThe successful operation of vermifi ltration systems can depend on the prevailing climate and the expected summer-winter temperatures, as they affect the worm’s survival. This is an important consideration in areas where the temperature drops drastically during winter months and also in areas where the temperature exceeds 40°C. Li et al. (2009) studied the impact of season on the treatment of sewage in vermifi ltration systems. The authors adjusted the HLR to correct the temperature fl uctuations to some extent by increasing the loading rate during summer months and decreasing it during winter month. It was found that the treatment effi ciency was not signifi cantly affected due to season fl uctuations, except on the coldest and hottest days (Li et al., 2009). Li et al. (2009) did note, however, that in very small vermifi ltration systems in very cold climates, there may be mortality of worms, as the systems may not be able to maintain suffi cient temperatures. However, more detailed investigation is required before concrete conclusions can be drawn.

3 Conclusion

Vermifi ltration provides a sustainable method for organic wastewater treatment with recycling of water and nutrients back into the environment. However, more detailed research is required to improve the effi ciency of vermifi ltration systems and make them a robust and effective commercial treatment system. In particular, factors such as

• the performance of worms in terms of growth, reproduction in the vermifi lter bed

• effect of different earthworm species on the treatment of wastewater

• feeding behaviour of worms fed with organic wastewater

• toxicity of various compounds to the worms in wastewater

• longevity of the system

• redox potential of the system should be researched further.

The study of potential harmful micro-organisms before and after the treatment is also desirable, as most of the wastewater contains harmful pathogens and there is need to analyse them before the treated water can be reused or discharged.

Vermifi ltration systems depend on living communities, i.e., worms and microbes, to treat waste. Factors like earthworm species and biomass, climatic conditions, the constituents of wastewater and water loading rate and retention time are the most critical in regards to system performance. The results from various studies indicate that vermifi ltration can be strongly recommended for rural settlements, small communities and small industries producing organic wastewater as a viable alternative to conventional treatment, provided that conditions are conducive for the growth of worms. However, there is still wide room for more detailed investigations to be made in this area for better application of this process.



ReferencesBajsa, O., Nair, J., Mathew, K., and Ho, G.E. (2004) ‘Vermiculture as a tool for domestic wastewater

management’, Water Science and Technology, Vol. 48, pp.125–132.Bhawalkar (1995) Vermiculture Ecotechnology, Bhawalkar Earthworm Research Institute, Pune, India.Biolytix (2003) BF6 Specifi cation, Maleny, QLD www.biolytix.com.au (Accessed: on 5/09/2010)Chaudhari, U. (2006) ‘Vermifi ltration of municipal wastewater (sewage) in Brisbane’, Thesis submitted

for Masters in Environmental Engineering, School of Environmental Engineering, Griffi th University, Brisbane.

Chiarawatchai, N., Nuengjamnong, C., Rachdawong, P. and Otterpohl, R. (2009) ‘Potential study of using earthworms as an enhancement to treat high strength wastewater’, The Thai Journal of Veterinary Medicine, Vol. 37, pp.25–32.

Davison, L., Headley, T. and Pratt, K. (2005) ‘Aspects of design, structure, performance and operation of reed beds-eight years experience’ in Northeastern New South Wales, Australia, Water Science and Technology, Vol. 51, pp.129–138.

Dominguez, J. (2004) ‘State-of-the art and new perspectives on vermicomposting research’, in Edwards, C.A. (Ed.): Earthworm Ecology, CRC press, Florida, pp.401–424.

Edwards, C.A. and Arancon, N.Q. (2004) ‘The use of earthworms in the breakdown of organic wastes to produce vermicomposts and animal feed protein’, in: Edwards, C.A. (Ed.): Earthworm Ecology, CRC press, Florida, pp.345–379.

Edwards, C.A. and Bohlen, P.J. (1996) Biology and Ecology of Earthworms, (3rd ed.), Chapman and Hall, London.

Eliasson, J. (2002) Rule Development Committee Issue Research Report- Draft- Hydraulic loading Rate, Washington state Department of health, http://www.doh.wa.gov/ehp/ts/WW/TechIssueReports/T-2HydraulicLoading-JME.pdf accessed on 15/09/2009

Gardner, T., Geary, P. and Gordon, I. (1997) ‘Ecological sustainability and onsite effl uent treatment systems’, Australian Journal of Environment Management,Vol. 4, pp.144–156.

Hawkins, C.L., Shipitalo, M.J., Rutledge, E.M., Savin, M.C. and Brye, K.R. (2008) ‘Earthworm populations in septic system fi lter fi elds and potential effects on wastewater renovation’, Applied Soil Ecology, Vol. 40, pp.195–200.

Hughes, R., Ho, G. and Mathew, K. (2006) ‘Conventional small and decentralised wastewater systems’, in Ujang, M.H.Z. (Ed.): Municipal Wastewater Management in Developing Countries: Principles and Engineering, IWA Publishing, London.

Hughes, R.J., Nair, J. and Ho, G. (2008) ‘The toxicity of ammonia/ammonium to the vermifi ltration wastewater treatment process’, Water Science and Technology, Vol. 58, pp.1215–1220.

Hughes, R.J., Nair, J. and Ho, G. (2009) ‘The risk of sodium toxicity from bed accumulation to key species in the vermifi ltration wastewater treatment process’, Bioresource Technology, Vol. 100, pp.3815–3819.

Hughes, R.J., Nair, J., Mathew, K. and Ho, G. (2007) ‘Toxicity of domestic wastewater pH to key species within an innovative decentralised vermifi ltration system’, Water Science and Technology, Vol. 55, pp.211–218.

Klein, J., Hughes, R.J., Nair, J., Mathew, K. and Ho, G. (2005, unpublished) Increasing the quality and value of biosolids compost through vermicomposting. Presented at ASPIRE, Asia Pacifi c regional conference on water and wastewater, Singapore, July, pp.10–15.

Li, Y-S., Xiao, Y-Q., Qiu, J-P., Dai, Y-Q. and Robin, P. (2009) ‘Continuous village sewage treatment by vermifi ltration and activated sludge process’, Water Science and Technology, Vol. 60, pp.3001–3010.

Li, Y.S., Robin, P., Cluzeau, D., Bouche, M., Qiu, J.P., Laplanche, A., Hassouna, M., Morand, P., Dappelo, C. and Callarec, J. (2008) ‘Vermifi ltration as a stage in reuse of swine wastewater: monitoring methodology on an experimental farm’, Ecological Engineering, Vol. 32, pp.301–309.

LIFE (2005) ‘ A new sewage treatment process: the vermifi ltration, a laymans report’, Direction d’Aide au Communes du Conseil Général de l’Hérault and European Commission – LIFE Projects,



Combaillaux, pp.1–11.Lismore city council Report (2009) The Use of Reed Beds for the Treatment of Sewage and Wastewater

from Domestic Households, http://www.clearwater.asn.au/resources/525_1.319_TI_JW_LismoreCouncilReebed.pdf (Accessed: 06/03/2009).

Loehr, R.C., Martin, J.H. and Neuhauser, E.F. (1988) ‘Stabilization of liquid municipal sludge using earthworms’, in Edwards.C.A. and Neuhauser, E.F. (Eds.): Earthworms in Waste and Environmental Management, SPB Academic Publishing, Hague, Netherlands, pp.95–110.

Loehr, R.C., Neuhauser, E.F. and Malecki, M.R. (1985) ‘Factors affecting the vermistabilization process: temperature, moisture content and polyculture’, Water Research, Vol. 19, pp.1311–1317.

Mobbs, M. (1998) Sustainable House, Choice Books, Sydney.Monk, E. (1995) ‘The removal of Phosphorous and faecal coliforms from greywater using a sandy soil,

bauxite residue and humus honours thesis’, School of Biological and Environmental Sciences, Murdoch university.

Otis, R.J. (1985) ‘Soil clogging: mechanisms and control, onsite wastewater treatment’, Proceedings of the Fourth National Symposium on Individual and Small Community Sewage Systems New Orleans, LA, 10–11 December 1984, ASAE, St. Joseph, MI, pp.238–250.

Parkin, T.B. and Berry, E.C. (1994) ‘Nitrogen transformations associated with earthworm cast’, Soil Biology and Biochemistry, Vol. 26, pp.1233–1238.

Pell, M. and Nyberg, F. (1989) ‘Infi ltration of wastewater in a newly started pilot sand fi lter system: reduction of organic matter and phosphorous’, Journal of Environmental Quality, Vol. 18, pp.451–457.

Philippe, M., Robin, P., Hamon, G., Qiu, J.P., Bouché, M., Cluzeau, D. and Callarec, J. (2006) Extensive Treatments For A Piggery With Minimal Pollution, http://www.rennes.inra.fr/umrsas/content/download/3297/37898/version/1/fi le/lombrifi cation (Accessed: 03/08/2009).

Sinha, R.K., Bharambe, G. and Bapat, P. (2007) ‘Removal of high BOD and COD loadings of primary liquid waste products from dairy industry by vermi-fi ltration technology using earthworms’, Indian Journal of Environmental Protection, Vol. 27, pp.486–501.

Sinha, R.K., Bharambe, G. and Chaudhari, U. (2008) ‘Sewage treatment by vermifi ltration with synchronous treatment of sludge by earthworms: a low-cost sustainable technology over conventional systems with potential for decentralization’, The Environmentalist, Vol. 28, pp.409–420.

Sinha, R.K., Nair, J., Bharamde, G., Patil, S. and Bapat, P. (2008b) ‘Vermiculture revolution: a low-cost and sustainable technology for management of municipal and industrial organic wastes (solid and liquid) by earthworms with signifi cantly low greenhouse gas emissions’, in Daven, J.I. and Klein, R.N. (Eds.): Progress in Waste Management Research, Nova Publishers, pp.159–228.

Smith, D.C. and Hughes, J.C. (2004) ‘Changes in maturity indicators during the degradation of organic wastes subjected to simple composting procedures’, Biological Fertility of Soils, Vol. 39, pp.280–286.

Spyridakis, D.E. and Welch, E.B. (1977) ‘Treatment processes and environmental impacts of waste effl uent disposal on land’, in Sanks, R.L, Asano, T. (Eds.): Land Treatment and Disposal of Municipal and Industrial Wastewater, Ann Arbor Science Publishers, Inc, Michigan.

Taylor, M., Clarke, W.P. and Greenfi eld, P.F. (2003) ‘The treatment of domestic wastewater using small-scale vermicompost fi lter beds’, Ecological Engineering, Vol. 21, pp.197–203.

Taylor, M., Clarke, W.P., Greenfi eld, P.F. and Swain, G.J. (2004) ‘Characterizing the physical and chemical properties of a vermicompost fi lter bed’, Compost Science and Utilization, Vol. 12, pp.383–391.

Tyler, E.J., Laak, R., McCoy, E. and Sandu, S.S. (1977) ‘The soil as a treatment system’, Onsite Wastewater Treatment, Proceedings of the Second National Symposium on Individual and Small Community Sewage Systems, Chicago, IL, 12–13 December 1997, ASAE, St. Joseph, MI, pp.22–37.



US EPA (2002) United States Environmental Protection Agency – Onsite Wastewater Treatment Systems Manual, EPA/625/R-00/008, U.S. EPA, Washington, DC.

Xing, M., Yang, J. and Lu, Z. (2005) ‘Microorganism-earthworm integrated biological treatment process––a sewage treatment option for rural settlements’, ICID 21st European Regional Conference, Frankfurt, www.zalf.de/icid/ICID_ERC2005/HTML/ERC2005PDF/Topic_1/Xing.pdf (Accessed: 18/04/2009).

Yang, J., Xing, M., Lu, Z. and Lu, Y. (2008) ‘A decentralized and on-site option for rural settlements wastewater with the adoption of vermifi ltration system’, 2nd International Conference on Bioinformatics and Biomedical Engineering, ICBBE 2008, Shanghai, pp.3023–3026.

Yang, J. and Zhao, L. (2008) ‘Wastewater treatment performance of earthworm biofi lter with fi lter media of quartz sand and ceramic pellet bioinformatics and biomedical engineering’, ICBBE 2008. The 2nd International Conference Shanghai, pp.3031–3034.


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