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Processing of human faeces by wet vermifiltration for improved on-site sanitation

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  • Bear Valley Ventures Ltd
Article

Processing of human faeces by wet vermifiltration for improved on-site sanitation

Abstract

The use of a vermifilter containing Eisenia fetida to degrade human faeces in a continuous wet system was explored. This paper aimed to understand the formation of vermicompost within the system, the quality of the effluent produced, and the effect of different bedding matrices. Eight filters were constructed, utilising four different bedding materials: four of these systems were seeded with 400 g of worms (vermifilters) while the others served as controls. The systems were flushed with 12 L of water per day and the experiment was split into five phases, each with different feeding regimes. Between 23.7 and 24.7 kg of fresh human faecal matter was added to the vermifilters over the 360 day period. The presence of the worms was found to increase the faecal reduction to 76% on average, compared to 17% in the control systems on average. Statistically significant reductions in phosphate, chemical oxygen demand and thermotolerant coliforms were achieved in the effluent of all vermifilters. The most suitable bedding matrix was a mixture of coir and woodchip. This study shows that there is potential for continuous treatment of human faeces using wet, on-site vermifilters.
Words: 4,950
Processing of human faeces by wet vermifiltration for improved on-site sanitation
C. Furlong1
Department of Civil and Environmental Engineering, Imperial College London, London,
SW7 2AZ, UK.
Email: claire.furlong@ymail.com
M.R. Templeton1
Department of Civil and Environmental Engineering, Imperial College London, London,
SW7 2AZ, UK.
Email: m.templeton@imperial.ac.uk
W.T. Gibson2
2Bear Valley Ventures Limited, Braeside, Utkinton Lane, Cotebrook, Tarporley, Cheshire,
CW6 0JH UK
Email: waltergibson@bearvalleyventures.com
Abstract
The use of a vermifilter containing Eisenia fetida to degrade human faeces in a continuous
wet system was explored. This paper aimed to understand the formation of vermicompost
within the system, the quality of the effluent produced, and the effect of different bedding
matrices. Eight filters were constructed, utilising four different bedding materials: four of
these systems were seeded with 400 g of worms (vermifilters) while the others served as
controls. The systems were flushed with 12 litres of water per day and the experiment was
split into five phases, each with different feeding regimes. Between 23.7 and 24.7 kg of fresh
1 Corresponding author
human faecal matter was added to the vermifilters over the 360 day period. The presence of
the worms was found to increase the faecal reduction to 96% in the vermifilters on average,
compared to 38% in control systems on average. Statistically significant reductions in
phosphate, COD and thermotolerant coliforms were achieved in the effluent of all
vermifilters. The most suitable bedding matrix was a mixture of coir and woodchip. This
study shows that there is potential for continuous treatment of human faeces using wet, on-
site vermifilters.
Keywords: Eisenia fetida, sewage, vermicompost, vermifilter, vermireactor, worm
Introduction
The majority of the world’s population relies on on-site, decentralised sanitation systems
such as pit latrines, cesspits, and septic tanks. One of the major problems associated with
these systems is that they require emptying, which can be costly, inconvenient and hazardous.
In high-density urban areas these problem are amplified, due to the lack of available space.
Emptying should ideally be undertaken by a vacuum pump truck, but tankers cannot gain
access to narrow streets and alleys (Thye et al., 2011). Alternative small-scale emptying
solutions have been developed to overcome these problems, e.g. the Gulper, MAPET (Thye
et al., 2011), but these technologies are still being trialled and may not be effective for all
sludge types. Worldwide approximately 200 million latrines and septic tanks must be
manually emptied each year by workers descending into the pit equipped with buckets and
spades (Thye et al., 2011). Furthermore, the final disposal of faecal sludge by any of these
methods is often simply by dumping into the immediate environment. This reintroduces
pathogens into the environment which were previously safely contained in the pit or tank. An
improved on-site sanitation solution needs to be identified which reduces the frequency of
required emptying of latrines, ideally together with achieving treatment of the waste so that
handling and disposal of the waste are safer activities.
An on-site worm-based system may be a solution to these problems. With this approach the
amount of solids within the system can potentially be reduced, due to the net loss of biomass
and energy when the food chain is extended by using worms. By reducing both the frequency
of emptying and the size of the system, this approach could be particularly suitable for highly
dense urban and peri-urban areas. Additionally worms are known to remove pathogens (from
sewage sludge) to the level where the waste can be safely applied to land (Eastman et al.,
2001), and the waste produced is dry compost (known as vermicompost) rather than a sludge,
which makes it easier to handle and transport.
In the field of sanitation research, studies using Eisenia fetida have concentrated on the
stabilisation of sewage sludge (Parvaresh et al., 2004), dried or pre-treated faecal matter
(Yadav et al., 2010;Yadav et al., 2011), or wastewater mixed with organic bulking agents
(Taylor et al., 2004). Pre-treatment was thought to be required as E. fetida died within an
hour of being introduced to fresh human faecal matter (Yadav et al., 2010). The importance
of the bedding layer, i.e. the matrix in which the worms live, was also noted, as they found
that E.fetida died when fed with human faeces without this support layer (Yadav et al., 2010).
Larger scale community worm-based systems have been trialled in China for the treatment of
sludge (Xing et al., 2011; Zhao et al., 2010) and sewage (Xing et al., 2010; Wang et al.,
2012). Commercial on-site systems are currently available, e.g. the Solid Waste Digester
(Simple Wastewater Solutions, 2010) and Biolytix™ (Biolytix, 2008), which are seeded with
worms and are attached to flushing systems. They are designed for use in rural locations in
developed countries but are cost-prohibitive for households in developing countries. They
also have large footprints for installation in an urban context and designed for waste
containing higher liquid content than is typical in developing countries.
Flushing systems are highly desirable in low-income urban and peri-urban contexts where
people strive for modernity. The advantages of systems with a water trap/seal include the
separation from one’s own and others’ waste, and the elimination of odours and flies, which
add to the desirability of flushing systems. This research was a part of a larger project which
used a people-led approach to sanitation improvement; therefore, in the light of these desired
benefits, the study focuses on flushing systems only. No other studies have investigated wet
(flushed with water periodically) worm-based systems for degrading fresh human faeces: as
such, experimental data were required to assess the feasibility of this approach for on-site
sanitation in developing countries.
The specific objectives of this work were to establish whether worms can continuously (the
systems are fed daily) degrade fresh human faeces under water-flushing conditions. To the
best of our knowledge all other laboratory based studies have been batch fed (fed weekly).
The system in the paper is described as ‘wet’ or ‘water-flushed’ whereas in traditional worm-
based systems water is only added to keep the system moist (e.g. Yadav et al., 2011) or a wet
slurry or sludge is added to the system (e.g. Xing et al., 2011), but no other studies have been
identified in which water was flushed through the systems to simulate the conditions in a
flushing sanitation system. Furthermore, this study was performed in order to determine
where and how much vermicompost is deposited and to assess the quality of the effluent
produced. Additionally, the effect of different bedding matrices on faecal solids reduction
(mass) and effluent quality was considered. The experiments were designed to replicate a
potential on-site wet worm based sanitation system, i.e. they were fed daily with fresh human
faeces and water was pumped into the filters to simulate flushing a toilet.
Methodology
Experimental systems
Eight filter systems were constructed from polypropylene boxes with internal dimensions of
L 37 x W 27 x H 25.5 cm and a surface area of 0.1 m2 (Figure 1). The base of each box
(except the sump box) was removed and replaced by plastic mesh with a 5 mm aperture and a
further mesh with a 1 mm aperture was placed on the bedding box mesh. Each unit consisted
of three boxes stacked on top of each other: the top box contained a 10 cm depth of bedding
matrices, the middle contained drainage media (plastic drainage coil with a 60 mm external
diameter, cut into 60 mm segments), and the bottom box was the sump which had a tap that
drained to a collection vessel. All components of the system were weighed separately to
allow for changes in mass to be calculated over time.
Four different bedding matrices were tested: coir (Fertile Fibres Ltd, Withington, UK),
woodchip (sourced from the Centre for Alternative Technology (CAT), Powys, Wales, UK),
a volumetric mixture of coir and woodchip (50:50), and a volumetric mixture of coir,
woodchip and vermicompost (33:33:33). Eight boxes were initially set up (two of each
bedding matrix type), with 400 g of E. fetida (worm density of 4 kg/m2) being added to one
of each matrix type (vermifilter), and the second corresponding box being used as a control
(did not contain worms). This worm density was selected from the estimation that 0.1 m2 of
vermifilter surface area could treat the waste from one person per day (approximately 200 g
of faeces, unpublished data) and a conservative estimate of worm feed consumption of 0.5 kg
feed/kg worm per day.
On top of the bedding a plastic mesh insert was placed and faecal matter was introduced on
top of this mesh (the faecal mesh, Figure 1). Each system was topped with a lid which
contained 40 1-mm randomly placed ventilation holes and an inlet for water additions. Water
was introduced using a peristaltic pump (Watson Marlow 502S, Cheltenham, UK) to simulate
flushing: approximately 12 litres of water was added during five watering periods spaced
throughout the day. This happened throughout the study apart from the resting period (Phase
4) when feeding was suspended to assess the ability of digestion to go to completion during
which only one litre of water was added per day to keep the systems moist.
Human faeces were collected daily from a series of bucket toilets at CAT. They were
homogenised through pooling and thoroughly mixed. Once a day the specified amount of
fresh faeces (Table 1) was placed on the faecal mesh. The variation in the expected feeding
regime (see phase descriptions in Table 1) and actual feeding regime (see mean feed addition
per day, Table 1) was due to the variations in the amount of faeces harvested. The reactors
were fed from Monday to Friday as it was not feasible to harvest faeces over the weekend:
therefore all the feed rates quoted in Table 1 are for a 5-day period.
Once the boxes were assembled they were wetted with six litres of water and allowed to drain
for one hour. The worms were then added and allowed to acclimatise for eight days without
feeding. The experiment was divided into five phases (Table 1) and ran for 360 days. The
reactors were housed in a heated building where the mean temperature was 22°C (Lascar EL-
USB-TC, Whiteparish, UK). A Lascar thermocouple and data logger and EC-5 moisture
probe (Decagon Devices Inc., Pullman, USA) were positioned in the middle of each bedding
layer.
Methods of analysis
All methods were chosen so they did not disturb or destroy the systems. Additionally, they
had to be undertaken under field conditions, due to the lack of standard laboratory facilities
on-site at CAT.
Moisture measurements (v/v %) were taken daily using ProCheck datalogger (Decagon
Devices Inc, Pullman, USA). A potting mixture calibration was used for all boxes except for
those containing only woodchip, when the perlite calibration was used. The laboratory and
box temperatures were measured hourly using a Lascar EL-USB-TC thermocouple. The
mass of faecal matter on the mesh above the bedding layer (faecal mesh, Figure 1) was
weighed separately.
The influent and effluent were analysed approximately weekly using Hach DR/890 field
testing kits (Loveland, USA) for chemical oxygen demand (Hach Method 8000), nitrate
(Hach Method 8039), nitrite (Hach Method 81532), and total phosphate (Hach Method
10127). Thermotolerant coliforms were analysed using a DelAgua Kit (Guildford, UK)
(Robens Centre, 2004). The effluent pH was measured using an electrode (pH703, TECPEL,
Taipei, Taiwan) and settleable solids were measured using standard methods (APHA, 1992).
All samples were analysed in duplicate and arithmetic mean for the samples are reported in
this paper (Table 2).
Data analysis
Waste stabilisation is reported in other papers (e.g. Yadav et al., 2011; Xing et al., 2011), and
this does not reflect the reduction in the mass of the waste. Mass reduction is important when
assessing this technology’s suitability for on-site sanitation, as it is directly related to the
necessary size of the system and emptying frequency. Mass reduction was calculated (Eq.1),
together with overall faecal reduction.
Equation 1: Weekly percentage faecal reduction
((TFMA W1FMRW1)/ TFMA W1) x 100
TFMA W1 = total faecal mass added onto mesh weekly
FMRW1 = faecal mass remaining on mesh at the end of the week
After 360 days the vermifilters were decommissioned and the undigested faeces on the faecal
mesh, the worm population and vermicompost were separated and weighed. The control
filters were decommissioned after 30 days due to the lack of overall decomposition (8-39%)
and the large amount of faecal matter that accumulated (0.73-1.1 kg).
Statistical analysis of results was carried out using SPSS 12.0.1. Student’s t-test was used to
compare data sets. One-way ANOVA was used to compare multiple data sets using the post-
hoc Tukey test. The null hypothesis of these tests was accepted if p>0.05.
Results and discussion
Reduction of faecal matter
In Phase 1 there was a statistically significant difference in the weekly percentage faecal
reduction between the filters and vermifilters for each bedding type (Student’s t-test coir
p=0.003; woodchip p=0.007; coir and woodchip p=0.008; coir, wood and vermicompost
p=0.006), confirming that the worms were actively degrading faecal material. Within the
controls, faecal reduction was higher for the filter containing vermicompost than for the other
types of bedding material (percentage feed reduction at the end of Phase 1: coir 11%,
woodchip 12%; coir and woodchip 11%; coir, wood and vermicompost 33%). This was
probably due to the vermicompost in the bedding matrices being microbiologically active.
There was no statistically significant difference between the weekly faecal reduction in the
vermifilters with different bedding matrices (ANOVA F(3,12)=1.177, p=0.359), therefore the
type of bedding did not affect the ability of the worms to consume faecal material during
Phase 1. The faecal reduction dropped in the vermifilters after the feed rate was increased at
the start of Phase 2 (Table 1). The systems became acclimatised to the new feeding rate after
approximately six weeks when 100% reduction was achieved; this pattern was repeated at the
start of Phase 5.
In Phase 1, this could be linked to the acclimatisation of the worms to the feed, sincein other
studies the worms were acclimatised prior to the experiments (Yadav et al., 2011), but in
subsequent phases it was more likely to be from the population adapting to the increased feed
rates, as this coincides with approximately the same amount of time required for a worm to
hatch and mature (Edwards & Lofty, 1997).
After approximately six months (26 weeks) vermicompost started accumulating on the faecal
mesh. This made it difficult to reliably measure faecal mass reduction beyond this point. Prior
to this period the mean weekly percentage faecal reduction across all vermifilters was
between 86-95% (this ranged from 23 to 176%). The variation was possibly due to the
mobility of the worms and their changing presence and absence on the faecal mesh. Feeding
continued during Phase 5 and at the end of the 360 day period a total of between 23.7 to 24.7
kg of fresh human faeces had been added to the vermifilters. At the end of Phase 5 the
amount of faeces remaining on the faecal mesh varied from 0.023-0.665 kg; the overall faecal
reduction was therefore 97 to 100%
The different components of the material on the faecal mesh at the end of the experiment
were separated and weighed. The highest mass of undigested faecal matter occurred in the
vermifilter containing coir bedding (coir 0.66 kg; woodchip 0.03 kg; coir and woodchip 0.15
kg; coir, wood and vermicompost 0.37 kg), which suggests that the rate of faeces
consumption by the worms was lower in this system. The highest mass of worms was found
on the faecal mesh when the bedding was a mixture of coir and woodchip (0.66 kg), followed
by the combination of coir, woodchip and vermicompost (0.47 kg), then woodchip (0.46 kg)
whilst the coir bedding had the lowest mass of worms (0.28 kg). It can be inferred from this
that coir alone is a less suitable bedding material, which may be because the worms prefer to
consume the coir compared to the faecal matter. Anecdotal evidence of this has been
highlighted in the general vermicomposting literature (Appelhof, 1997).
The worm density increased in all vermifilters: from 4 kg/m2 to 8.56 kg/m2 in the coir
vermifilter; to 10.10 kg/m2 in the woodchip and coir vermifilter; to 13.19kg/m2 in the
woodchip, coir and vermicompost vermifilter and to 14.48 kg/m2 in the woodchip vermifilter.
This contradicts earlier studies (Yadav et al., 2010; Yadav et al., 2011) which found that a
worm density of 4 kg/m2 was unsustainable. The conditions within their filters and the ones
reported in this paper were very different, i.e. feeding regimes, application of feed, water
flow, and bedding type, all of which could affect the health of the worm population.
Additionally other authors have reported increased worm density over time: Zhao et al.(2010)
reported that worm density increased from 32g/L to 55.7g/L over a period of six months and
Lui et al. (2012) reported a worm density increase from 32 g/L to 46.3 g/L over a seven
month period. The feed in both of these studies was sewage sludge diluted with water,
suggesting that higher worm densities may be sustainable in wetter systems.
Vermicompost was deposited throughout the vermifilter systems, though the majority was
retained in the upper part of the system, i.e. the bedding layer and faecal mesh combined. The
rate of accumulation of vermicompost over the period of the experiment was between 2.7 and
4.1 kg/year (coir 4.1 kg; woodchip 2.7 kg; coir and woodchip 4.0 kg; coir, wood and
vermicompost 4.1 kg). The lower mass accumulated in the system using woodchip was
probably due to the coarser filtering action of the woodchip, with vermicompost being
washed through the bed. Additionally, it could be also attributed to the worms inability to
convert this material into vermicompost. A higher mass of vermicompost (1.6 kg) was found
on the faecal mesh of the vermifilter containing the coir and woodchip bedding (compared to
coir 0.75 kg; woodchip 1.3 kg; coir, woodchip and vermicompost 1.3 kg), because of more
worms inhabiting this part of the system compared to the other vermifilters. This suggests
that this layer was more active in this vermifilter because of the bedding type. A higher
proportion of vermicompost was deposited or formed in the bedding layer of the coir system
(2.43 kg) (compared to woodchip 0.92 kg; coir and woodchip 1.7kg; coir, woodchip and
vermicompost 2.1 kg), which supports the hypothesis that the worms preferred to consume
the bedding in this system rather than the faecal matter.
All of the vermifilter communities remained aerobic and healthy over the 360 days as
assessed by visual and olfactory inspection. The vermifilters were fed 200 g of faecal matter
on 40 days in Phase 5, which is the mean amount of faeces produced per person per day.
Therefore this size of vermifilter (a surface area of 0.1 m2) has the potential to treat the waste
from one person. This would lead to a household system that is considerably smaller than
traditional on-site sanitation systems such as septic tanks or pit latrines.
Effluent quality
The volume of vermicompost in the effluent during Phase 5 was measured as settleable
solids, as the vermicompost was dense and settled out readily (Zhao et al., 2010). The mean
settleable solids in the effluent were highest in the filter containing woodchip (4.9 ± 1.4
mL/L) compared to coir (4.0 ±1.3 mL/L), woodchip and coir (3.8 ± 1.4 mL/L) and woodchip,
coir and vermicompost (3.0 ± 1.1 mL/L) as woodchip was a coarser filter, which led to more
vermicompost being washed through the vermifilter. However, no statistical difference was
found (ANOVA F(3,32)=1.374, p=0.269).
The pH of the influent generally increased as it passed through the vermifilter (influent mean
pH 6.21, effluent mean pH 6.70). Earlier studies have also recorded this (Xing et al., 2010)
and it was expected, as vermicompost is known to have a higher pH than the waste being
processed by the system (Appelhof, 1997). This is thought to be due to the waste being
neutralised by secretions from the worms’ intestines and by the ammonia which is excreted
by worms (Edwards & Lofty, 1997).
Table 2 summarises the mean quality of the influent and effluent from all the boxes.
Phosphate was removed in the system, which contrasts earlier findings (Taylor et al., 2004)
where phosphate levels increased because of the leaching of phosphate from the
vermicompost bedding/filter media. The mean total phosphate removal was 24% in Phase 2,
47% in Phase 3 and 58% in Phase 5, with no difference in the removal rates for the different
bedding types (ANOVA F(3,28)=0.718, p=0.550). A more recent study (Wang et al., 2011)
supports these findings with a mean total phosphate removal of 98.4%, when lower levels of
total phosphorus (5.05 to 9.88 mg/L) were present in the domestic waste water being treated
(Table 2). Phosphorus removal in vermifilters has been attributed to a number of processes,
including the direct absorption of phosphorus by growing cells, the enhanced storage of
phosphorus as polyphosphorus by bacteria in the system and precipitation of phosphorus
(Wang et al., 2011).
Nitrate levels increased as the effluent passed through the system, indicating that nitrification
(conversion of ammonia to nitrate) was occurring. This has also been reported in a previous
study of vermifiltration of domestic sewage (Wang et al., 2011). An earlier study (Taylor et
al., 2004) reported that denitrification also occurred, but the bedding depth in that study was
50 cm which would have better created anoxic conditions than in the present study.
In Table 2 it can be seen that higher COD levels were observed during Phase 1 in the
vermifilters compared to the control systems. No statistical difference was observed when
paired analysis was undertaken (t-test coir p=0.02; woodchip p=0.79; woodchip and coir
p=0.13; woodchip, coir and vermicompost p=0.69), except in the systems using a coir
bedding matrix. This was possibly because coir is inert, coupled with its filtering capacity.
As the majority of the COD is contained in the faecal matter and the bedding layer acts a
filter for this material, it was hypothesised that higher COD levels would be found in the
effluent in the vermifilters with coarser bedding materials. The type of bedding material did
not affect the effluent quality across all phases (ANOVA F (3,80)=1.574, p=0.202). At the
start of each new experimental phase when the feed level was increased, there was a general
decreased in the COD removal until the system stabilised, it increased and then remained
relatively constant. The mean COD removal achieved during Phase 5 (Table 2) was 86-87%,
which is comparable to the 81% removal which was reported in a previous study using a
multi-stage vermifilter (Wang et al., 2011). It should be noted however that the COD in the
influent their study was much lower, as it was rural domestic wastewater. The system tested
also had higher levels of COD removal compared to levels found in septic tanks (47%, Lowe
et al., 2009) and other vermifilter pilot studies (47-58%, Zhao et al., 2010); one vermifilter
study actually found that COD in the effluent increased (Taylor et al., 2003).
The thermotolerant coliform removal across all the boxes ranged from 1-log to 3-log with the
mean removal being 2-log.There was no statistically difference in the removal of
thermotolerant coliform bacteria across all vermifilters (ANOVA F(3,32) =1.02, p=0.399).
The removal reported in this paper are higher than those obtained in a more complex full-
scale worm-based (1-log to 2-log removal, Weiss & Scholes, 2007) and septic tanks (1-log
removal, Lowe 2009), although it may be that in these studies the influent was more dilute.
No experimental studies have been found reporting the bacteriological effluent quality of pit
latrines, possibly due to the difficulty in obtaining a sample.
Implications for on-site sanitation systems
From the data it can be seen that this technology has the potential for on-site sanitation
applications. The worms have the ability to feed on fresh human faeces under flushing
conditions, meaning the vermifilter can be coupled with a low volume pour-flush system,
which brings the additional benefit of a water seal (although it should be noted that the
vermifilter was aerobic and therefore did not smell). Additionally the system proved to be
robust and the worm populations survived periods when they were not fed (Phase 4) and
periods of variable feeding (Phase 5). The conversion of faeces to vermicompost in the
system was between 11 and 18% by mass. Using these conversion values it can be calculated
that annually faeces from 10 people (720 kg) would be converted to between 79 and 130 kg
of vermicompost. This is thought to be a conservatively low estimate of the mass of the
vermicompost generated, as being biologically active it is thought that it would breakdown
further in the system. Furthermore, it should be noted that this system was running for almost
a full year (360 days) and the vermicompost accumulation over time did not cause any
blockages in the system or other practical operational problems.
Results from this paper suggest that at full scale, a system could be very compact, possibly
having an area of 1m2 and depth of 0.9 m to serve a household of 10 people. The performance
of the system in terms of solids reduction and effluent quality looks promising and potentially
superior to existing options for low income families. Although the effluent quality from this
system would not be high enough for direct discharge into a water courses, it is of a standard
where it could be infiltrated into the soil where it would be further treated by the in-situ soil
microorganisms, which is the same strategy used currently with septic tanks and pit latrines
in developing countries. As the system trialled in this paper was extremely simple and
flexible (i.e. different materials of construction could be used) this makes it highly adaptable
for use in developing countries’ contexts. Additionally the worms used are found worldwide,
but other local species could be trialled.
Conclusions
This study was undertaken to test the feasibility of a wet vermifilter for processing fresh
human faeces. The presence of the worms increased the faecal reduction rates compared to
the control systems. The effluent quality from these simple vermifilter was found to be higher
than from septic tanks, and other vermifilter systems. A surprising finding from this study
was the high worm density that the wet system supported. The findings of this paper suggest
that this technology has the potential to develop into a new type of on-site sanitation system
for developing countries; because of the estimated small size of these systems, they would be
particularly suited to high density urban and peri-urban areas.
Acknowledgements
The authors acknowledge the support of the Bill and Melinda Gates Foundation through a
grant (OPP52641) to the London School of Hygiene and Tropical Medicine. The authors also
acknowledge the Centre for Alternative Technology, Wales for hosting this research and to
all of those from this centre who contributed to the research, especially Jamie McQuilkin and
Margaux Taillade.
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Figure Captions
Figure 1: Experimental configuration
... The Tiger Toilet was developed to address these concerns [6,7]. It involves using worms (tiger worms, Eisenia fetida) to transform faecal matter into vermi-compost and an effluent liquid that is treated to an environmentally safer standard than that from traditional pit latrines. ...
... For example, in China, worms have been used to treat wastewater and sewage [8][9][10], and to continuously treat wet sludge at the village scale [11]. However, Furlong et al. [6] were the first to show that tiger worms could effectively degrade human faeces in a continuous, flushed system for use in an onsite, household-scale sanitation system. The vermifiltration design was improved during the pilot phases of technology development by testing different bedding layers, worm masses, feed rates and feed methods to make for simpler construction and reduced cost. ...
... The bedding depth above the graded media layer was used to estimate the fill rate. At the initiation stage, the depth in the digester was comprised of a layer of biomedia seeded with tiger worms [6,7]. Over the subsequent months and years, vermi-compost accumulated from the breakdown of faecal matter. ...
Article
Tiger Toilets use a worm-based ecosystem to degrade human waste and have recently been demonstrated as a cost-effective innovation in on-site sanitation. The benefits over traditional pit latrines include slower fill rate, fewer odours, and safer emptying. However, a question remains around how to measure the rate of accumulation of vermi-compost and predict the fill rate into the future. In this study, fifteen Tiger Toilets of varying installation ages in the villages of Jejuri, Bhalgudi and Walhe/Adachiwadi, in Maharashtra province, India were investigated to determine the rate of filling. A laser measure was used to define cross-sections of the depth to vermi-compost layers within the Tiger Toilet digesters. Bench-scale column tests were used to estimate liquid infiltration rates from the digesters into the surrounding soils. Changes over time in the interior digester conditions were photographed and a video camera was installed in selected digesters to confirm and observe the worm activity in situ under red light. Calculated fill rates of the Tiger Toilets were significantly lower compared to estimated fill rates of traditional pit latrines of a similar size and usage rate. The infiltration of the liquid fraction of the waste into the surrounding soil was observed to be a key factor in filling.
... Wang et al. (2013) reported 80-82% removal of TP using bedding material which consists of cobblestone, detritus, silver sand and earthworm bed while removal of 87% of TP using cobblestone, soil and sawdust. Furlong et al. (2014) obtained a removal efficiency of TP in the range of 56-59% in human faeces. ...
... Further, Kumar et al. (2016) have treated domestic wastewater with vermifiltration and achieved a reduction of FC by 99%. An experimental run of 365 days of vermifiltration showed the reduction of COD by more than 87 and 99% thermotolerant coliforms using domestic wastewater (Furlong et al. 2014). ...
... Vermicomposting has been shown to be successful in processing sewage sludge and solids from wastewater, food industry waste, urban residues, and food and animal waste (Domínguez et al. 2003;Clarke et al. 2007;, Suthar 2007Dominguez and Edwards 1997;Aira et al. 2006a, b;Lazcano et al. 2008). There has been a report on the reduction of COD of about 87% through vermicomposting of human feces (Furlong et al. 2014). ...
Chapter
The pronounced and major effects of contamination of the environment with heavy metals and other xenobiotic compounds have become a major problem worldwide. Soil contaminated with heavy metals poses serious threat to plants, animals as well as human health. Heavy metals due to their toxicity reduces the soil fertility, affects the plant photosynthetic efficiency, reduces yield of the crops, and causes nutrient imbalance. Phytoremediation an eco-friendly, clean, and green technology helps to remove contaminants from the polluted soils. The use of beneficial microorganisms along with plants is considered as an effective method for increasing the efficiency of remediation of contaminated soils. Earthworms also play an important role in remediation process. Interaction of plants with microflora plays a vital role in bioavailability of the metals and their bioaccumulation in plants.
... The authors revealed that plants and earthworms play an essential role in managing feedlot runoff together. Vermifiltration are also useful to the human faeces (Furlong et al., 2014(Furlong et al., , 2015. The authors have reported about 87% of COD reduction during vermifiltration of human faeces. ...
... Vermifiltration (VF) is an example of the later, recognized as a low-cost and sustainable technology to treat wastewater (Jiang et al., 2016, Kadam et al., 2009, sewage sludge (Zhao et al., 2010) and fecal matter (Furlong et al., 2014(Furlong et al., , 2015(Furlong et al., , 2016. ...
Thesis
This thesis presents results from studies on vermifiltration as a nature based solution for small decentralized WWTP. The purpose of the research was to support the leveraging of technical activities of a private company, which supported the study both materially and with dedication time.
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The world is currently undergoing a paradigm shift towards a circular society in which resources are recovered and reused rather than discarded. The global population has surpassed seven billion people, and rapid urbanisation in many areas is putting a significant strain on our ability to provide basic services to all. The Sustainable Development Goals highlight the fact that millions still lack access to food, healthcare, water and sanitation. At the same time, it is increasingly evident that we are consuming the Earth’s resources and releasing waste into the environment in an unsustainable manner. The resulting effects on climate change, biodiversity loss and changing nutrient cycles threaten to over-step critical planetary boundaries. Crossing these boundaries has the potential to cause irreversible environmental change and to threaten the ability of humanity to develop and thrive. Sanitation systems manage carbon, nutrient and water flows, which are key resource flows that affect the planetary boundaries and thus should be recovered and recirculated instead of being released into the environment. Increasing resource recovery within our sanitation systems can play a critical role in shifting to a more sustainable society. There are significant resources within excreta and wastewater fractions that can be recovered and turned into useful products. For example, the average person excretes 4.5 kg of nitrogen, 0.5 kg of phosphorus and 1.2 kg of potassium every year. These elements and other micronutrients found in excreta are critical for the fertilising and restoration of agricultural soils. The energy value of faeces is on average 4 115 kcal/kg of dry solids. This energy can be utilised as a renewable energy source. On top of this, there are large volumes of wastewater that can be captured, cleaned and reused. However, human excreta and wastewater contain pathogens and other undesired substances, risks that need to be managed in a reuse system. The growing demand for recycling needs to be complemented with a growing knowledge of how to do it safely. The aim of this document is to provide an overview of the possibilities for resource recovery from sanitation and provide guidance on treatment processes to achieve safe products for reuse. The focus of this document is on resource recovery from the organic wastes managed in sanitation systems and, to a lesser extent, on the recovery of water and energy generation. Resource recovery sanitation systems are defined as systems that safely recycle excreta and organic waste while minimising the use of non-renewable resources such as water and chemicals. Safe recycling means that waste flows are managed so that physical, microbial and chemical risks are minimised. Thus, the recycled product should not pose any significant health threat or environmental impact when correctly used.
Article
There is a growing need to reclaim wastewater for agricultural use due to freshwater limitation. Integrating macrophytes in vermifiltration improves the treatment efficiency. However, the effect of treated wastewater on seed germination and seedling development is not widely investigated. The study investigated the use of Pistia stratiotes in a macrophyte-assisted vermifiltration of domestic wastewater and assessed the effect on seed and seedling development of Zea mays, Triticum aestivum and Sorghum bicolor. Three irrigation treatment water wee applied; macrophyte-assisted vermifiltration (VP), no macrophyte vermifiltration (VM) and potable water (PW), as the control. Results showed that VP had a removal of 41–44% EC, 65–67% turbidity, 52–65% TDS, 67–70% TSS, 29–34% COD, 42–46% BOD, 67–70% N tot, and 74–78% P avail compared to VM. VP treatment reduced inhibition in the morphological, physiological and biochemical developments of seed and seedling growth. The use of macrophyte-vermifiltered wastewater significantly (p < 0.05) increased the percentage of germination and the radical length of all seed species increased as well. In terms of the seedling development, seedling mortalities were significantly (p < 0.05) reduced and more than 75% Chlorophyll pigments estimations (Cɑ, Cɓ, Cɑ+ɓ and Cx+c) were identified in all seedling species when macrophyte-vermifiltered wastewater was used to irrigate.
Article
Vermifiltration is an emerging low-cost and environmentally sustainable technology for the treatment of wastewater and recovery of nutrients. This study evaluated, for 6 months, the efficacy of a pilot-scale vermifilter for the treatment of a side-stream of dairy wastewater at a commercial dairy farm in Washington State. Samples of dairy wastewater were collected at the upstream and downstream of the vermifilter during these six months and analyzed for reductions in the solid contents (total solids (TS) and total suspended solids (TSS)), chemical oxygen demand (COD), pertinent nitrogen species (total nitrogen (TN), total ammonia-nitrogen (TAN), nitrate-nitrogen (NO3-N), and phosphorus species (total phosphorus (TP) and orthophosphate (Ortho-P)). The results indicated that investigated. The respective reductions were 81 ± 7.1% for TAN, 77 ± 8.4% for TN, and 74 ± 9.5% NO3-N. Total solids reduction was, generally, low at 21 ± 7.0% but the reduction of TSS was significantly high at 68 ± 10%. Results indicated modest reductions of TP (48 ± 6.0%) and COD (45 ± 4.1%), but relatively lower Ortho-P reduction (3.9 ± 19.2%). Regression modeling showed that ambient temperature has a significant influence on the reduction efficiencies of TAN (by as much as 50%) and COD (by as much as 59%). Overall, this study demonstrated that vermifiltration has great potential in alleviating nutrients contents and simultaneously reducing organic strength of the vermifilter effluents.
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Solid and liquid waste (SLW) has become one of the serious problems and leads to significant damage to the environment and public health. With the increasing and fast-approaching water crisis, it is extremely essential to effectively treat the SLW before it enters the water bodies. The contamination of soil and water is increasing due to various anthropogenic activities, which has alarmed the scientific community. Different methods like thermal methods, landfilling, etc. for solid waste and primary, secondary, and tertiary treatment for liquid waste are being practiced worldwide. But, they seem to produce harmful gases, leachate, thereby affecting the environment and human health, and they are of high costs in installation and maintenance. Therefore, there is an urgent need for cost-effective and eco-friendly techniques for addressing these concerns. Thus, this chapter focuses on vermitechnology-using earthworms, like vermicomposting and vermifiltration to manage various types of solid and liquid waste like industrial sludge, food waste, animal waste, etc. into vermicompost (nutrient-rich manure) which acts as a soil conditioner and purifies the wastewater.
Chapter
With the rapid population growth and wastewater generation due to anthropogenic activities, availability of freshwater is decreasing annually. Untreated wastewater discharged from the municipal and industrial sectors reaches to the local surface water bodies and degrades water quality. Conventional wastewater treatment systems possessing high carbon footprint require mechanistic operations and need to be made affordable with ease of operation. To overcome the impediments associated with the conventional treatment systems, vermifiltration technique employing earthworms in a filter bed has emerged as an alternative for wastewater treatment and recycling. Further, the potential of macrophyte has also been explored by integrating with the vermifiltration system for wastewater treatment. This chapter presents the applicability of vermifiltration technique with various filter design configurations and mechanisms involved for the treatment and recycling of both sewage and industrial effluents. Further, the influence of different operational parameters like hydraulic retention time (HRT), organic loading rate (OLR), hydraulic loading rate (HLR), filter media bed design, earthworm density and flow mode on organic, nutrient and pathogen removals from domestic and industrial wastewater is discussed concisely. Moreover, future perspectives have been provided towards the improvement of the efficacy of the vermifiltration system for wastewater treatment and recycling.
Article
In Burkina Faso, faecal sludge is mostly discharged into the environment untreated, with associated public health risks. Thus, sanitation technology that efficiently treats Blackwater (BW) in-situ is urgently required. This paper reports the design and testing of a proposed worm-based toilet (wormlet). The presence of E.eugeniae (EE) is found to reduce the total accumulated BW by a maximum of 61.74%. Over five to ten weeks, 1 kg of BW (dry portion) can be processed to 0.49–0.61 kg of vermicast by the EE. The wormlet effluent is of superior quality, as the log 10 removal efficiency of the bedding and filter matrix reached 7.45 and 5.85 for E. coli and faecal coliform, respectively. Helminth egg removal was found to be 97% within the 75-cm depth. Average organics and nutrient removal efficiencies are 99–100% for total solids and total suspended solids; 99% and 98% for the biochemical and chemical oxygen demand, respectively. Removal efficiencies between 97 and 99% were found for NH4⁺, NO3⁻, NO2⁻, and PO4³⁻. A 100% turbidity removal was found in the systems containing charcoal. Thus, the wormlet appears to be superior for in-situ BW treatment, generating sub-products that can be reused or safely discarded.
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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. fetida was 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.
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A vermifilter system packed with quartz sands and ceramsite was studied for domestic wastewater treatment. Results showed that good performance of vermifilter was achieved and removal rates were COD (47., respectively. An increase in hydraulic loading led to a decrease in treatment efficiency and adult earthworm abundance. In addition, activities of protease, alkaline phosphatase (ALP), and cellulase in earthworm body dropped, but superoxide dismutase (SOD) and catalase (CAT) increased with the hydraulic loading. Correlation analysis implied that larger earthworm (>0.3 g) abundance might play more positive role on wastewater treatment in vermifilter, compared to smaller worm. Earthworm enzymatic activities had significant correlation with treatment efficiency of COD and BOD 5 by vermifilter. Thus an important relationship exists for earthworm population dynamics and enzymatic activities with COD and BOD 5 removal rates of domestic wastewater by vermifilter.
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The performance of a conventional biofilter (BF) and a vermifilter containing the earthworm, Eisenia foetida, (VF) for the treatment of domestic wastewater sludge were compared with the earthworm-microorganism interaction mechanisms involved in sludge stabilization. The results revealed that the presence of earthworms in the VF led to significant stabilization of the sludge by enhancing the reduction in volatile suspended solids (VSS) by 25.1%. Digestion by earthworms and the earthworm-microorganism interactions were responsible for 54% and 46% of this increase, respectively. Specifically, earthworms in the VF were capable of transforming insoluble organic materials to a soluble form and then selectively digesting the sludge particles of 10-200 microm to finer particles of 0-2 microm, which led to the further degradation of organic materials by the microorganisms in the reactor. Additionally, denaturing gradient gel electrophoresis (DGGE) profiles showed that there was an intensified bacterial diversity in the vermifilter due to the presence of earthworms, especially in response to the nutrients in their casts.
Article
Pit latrines are the most common forms of sanitation in urban slums and unplanned settlements in developing countries. Often, little consideration is given to how to deal with the pits once they fill up. The authors summarize pit emptying technologies that have been designed to date to overcome the problem of fecal sludge management in such settings and presents a framework to assist decision makers in identifying potential pit emptying methods based on local technical conditions.
Article
Previous studies have shown that the stabilization of excess sludge by vermifiltration can be improved significantly through the use of earthworms. To investigate the effect of earthworms on enhancing sludge stabilization during the vermifiltration process, a vermifilter (VF) with earthworms and a conventional biofilter (BF) without earthworms were compared. The sludge reduction capability of the VF was ∼85% higher than that of the BF. Specifically, elemental analysis indicated that earthworms enhanced the stabilization of organic matter. Furthermore, earthworm predation strongly regulated microbial biomass while improving microbial activity. Denaturing gradient gel electrophoresis (DGGE) analysis showed that the most abundant microbes in the VF biofilms and earthworm casts were Flavobacterium, Myroides, Sphingobacterium, and Myxococcales, all of which are known to be highly effective at degrading organic matter. These results indicate that earthworms can improve the stabilization of excess sludge during vermifiltration, and reveal the processes by which this is achieved.
Article
The performance of a novel three-stage vermifiltration (VF) system using the earthworm, Eisenia fetida, for rural domestic wastewater treatment was studied during a 131-day period. The average removal efficiencies of the tower VF planted with Penstemon campanulatus were as follows: chemical oxygen demand, 81.3%; ammonium, 98%; total nitrogen, 60.2%; total phosphorus, 98.4%; total nitrogen, mainly in the form of nitrate. Soils played an important role in removing the organic matter. The three-sectional design with increasing oxygen demand concentration in the effluents, and the distribution of certain oxides in the padding were likely beneficial for ammonium and phosphorus removal, respectively. The microbial community profiles revealed that band patterns varied more or less in various matrices of each stage at different sampling times, while the presence of earthworms intensified the bacterial diversity in soils. Retrieved sequences recovered from the media in VF primarily belonged to unknown bacterium and Bacilli of Firmicutes.
Article
The main objective of the present study was to determine the optimum stocking density for feed consumption rate, biomass growth and reproduction of earthworm Eisenia fetida as well as determining and characterising vermicompost quantity and product, respectively, during vermicomposting of source-separated human faeces. For this, a number of experiments spanning up to 3 months were conducted using soil and vermicompost as support materials. Stocking density in the range of 0.25-5.00 kg/m(2) was employed in different tests. The results showed that 0.40-0.45 kg-feed/kg-worm/day was the maximum feed consumption rate by E. fetida in human faeces. The optimum stocking densities were 3.00 kg/m(2) for bioconversion of human faeces to vermicompost, and 0.50 kg/m(2) for earthworm biomass growth and reproduction.
Article
Reduction and stabilization of sewage sludge during the clarification of municipal wastewater was synchronously shown to be improved significantly in a pilot-scale vermifiltration using an epigeic earthworm Eisenia fetida. The present study aimed to select a better filter media suited to vermifiltration performance by the comparisons of sludge yields, the characteristics of the by-products of vermifiltration-vermicast and the abrasions of earthworms between ceramsite and quartz sand. It was observed that the sludge yield of the CVB (Ceramsite Vermibed) ranged from 0.07 to 0.09 kg SS/kg COD(removed) at ambient temperature of 4-29 °C, representing 81% and 50% lower than that of the SVB (Quartz Sand Vermibed) and other reduction systems mentioned in this study. In addition, the sludge morphology variations described that the vermicast sludge from the CVB was more completely digested by earthworm than that of the SVB. The abrasions of the body wall of the earthworms in the CVB depicted less injured than that of in the SVB. So the ceramsite as filter media was better suited for the vermifiltration than the quartz sand.
Article
The aim of this study is to quantity the effect of filter bed depth and solid waste inputs on the performance of small-scale vermicompost filter beds that treat the soluble contaminants within domestic wastewater. The study also aims to identify environmental conditions within the filters by quantifying the oxygen content and pH of wastewater held within it. Vermicompost is being utilised within commercially available on-site domestic waste treatment systems however, there are few reported studies that have examined this medium for the purpose of wastewater treatment. Three replicate small-scale reactors were designed to enable wastewater sampling at five reactor depths in 10-cm intervals. The surface of each reactor received household solid organic waste and 1301 m(-2) per day of raw domestic wastewater. The solid waste at the filter bed surface leached oxygen demand into the wastewater flowing through it. The oxygen demand was subsequently removed in lower reactor sections. Both nitrification and denitrification occurred in the bed. The extent of denitrification was a function of BOD leached from the solid waste. The environmental conditions measured within the bed were found to be suitable for earthworms living within them. The study identified factors that will affect the performance and application of the vermicompost filtration technology. (C) 2004 Elsevier B.V. All rights reserved.
Article
Rural sewage treatment is now paid more and more attention in China. Vermifiltration technology could be one of the practical options under the review of previous studies. It showed good removal rates of contaminants on small to pilot scales for short-term tests. However, the impacts of season, temperature or other unknown factors are usually not taken into account. In this study, a larger vermifilter was designed to treat the sewage on village scale for long-term operation. Filter material composition was optimized by a half year experimentation. The treatment effects of vermifiltration were also compared with traditional activated sludge process for the same influent sewage. The results showed that the designed vermifiltration system could continuously treat the sewage produced by more than 100 inhabitants per day. COD, BOD5 and SS concentration in outflow were rather stable despite the fluctuation of hydraulic loading rate and organic input during one year test. It can also remove N and P to some extent. A suspending design of vermifilter bed cause adequate oxygen content in outflow of vermifilter. The comparative test showed that the treatment efficacy of vermifiltration was similar as activated sludge process. Generally, this vermifiltration system has practical application value for village sewage treatment.