608 Practical Paper © IWA Publishing 2015 Journal of Water, Sanitation and Hygiene for Development | 05.4 | 2015

Practical Paper

The development of an onsite sanitation system based on vermifiltration: the ‘Tiger Toilet’ C. Furlong, W. T. Gibson, M. R. Templeton, M. Taillade, F. Kassam, G. Crabb, R. Goodsell, J. McQuilkin, A. Oak, G. Thakar, M. Kodgire and R. Patankar

ABSTRACT

This paper describes the development of a novel onsite sanitation system based on vermifiltration, C. Furlong W. T. Gibson the ‘Tiger Toilet’. Initial laboratory experiments demonstrated that feed distribution was not required, Bear Valley Ventures Limited, Braeside, Utkinton Lane, Cotebrook, Tarporley, 2 a worm density of 2 kg/m could be used, worms preferred wetter environments, and system Cheshire CW6 0JH, UK configuration did not affect effluent quality. Installing the first prototype in the UK proved that the C. Furlong (corresponding author) process functioned when scaled, i.e., chemical oxygen demand and thermotolerant coliform M. R. Templeton reduction were found to be comparable with the laboratory results. Ten prototypes were then tested F. Kassam Department of Civil and Environmental by households in rural India; all were working well after six months. The vermifilters were processing Engineering, Imperial College London, London SW7 2AZ, the amount of faeces entering the system on a daily basis, so faeces was not accumulating. It was UK fi E-mail: [email protected]; c.furlong@lboro. estimated that they would require emptying after approximately ve years, based on the depth of the ac.uk

vermicompost generated. With further development, it is believed that the Tiger Toilet has the M. Taillade potential to become a superior form of onsite sanitation, when compared with traditional onsite G. Crabb R. Goodsell sanitation technologies. J. McQuilkin Centre for Alternative Technology, Key words | Eisenia fetida, faecal sludge, India, sewage, worms Llwyngwern Quarry, Pantperthog, Machynlleth, Powys SY20 9AZ, UK

A. Oak G. Thakar M. Kodgire R. Patankar PriMove Pvt Ltd, Bhusari Colony, Saudamini Complex, Paud Rd, Kothrud, Pune, India

INTRODUCTION

The majority of the world’s population has little choice in terms by dumping into the immediate environment, thereby reintro- of onsite sanitation technology. Most rely on pit latrines, cess- ducing pathogens which were previously safely contained in pits and septic tanks. A major problem associated with these the pit or tank. New onsite sanitation technologies need to systems is that they require emptying, which can be costly, be developed which reduce the frequency of emptying and inconvenient and hazardous. Approximately 200 million which not only contain, but also treat the waste, so that hand- latrines and septic tanks worldwide must be manually emptied ling and disposal are safer activities. each year, by workers descending into the pit equipped with Worm-based sanitation may provide a solution, since buckets and spades (Thye et al. ). Furthermore, the final dis- solids are further reduced by the net loss of biomass and posal of faecal sludge by any of these methods is often simply energy when the food chain is extended with worms (Xing

doi: 10.2166/washdev.2015.167

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et al. ). This approach has the potential to reduce both used previously (Furlong et al. ). Human faeces were the frequency of emptying and the size of the sanitation harvested and the vermifilters were fed as in Furlong et al. system. Furthermore, worms have the ability to reduce () with the amount specified in Table 1. The exception pathogens to the level where the by-product (vermicompost) was V4 where it was spread across the surface to assess can be safely applied to land (Eastman et al. ).Vermi- feed dispersion. This experiment was split into four phases compost is dry and soil-like, making it easier to handle with different feeding regimes (Table 1). A resting phase and transport. was incorporated due to a lack of feed and staff over a holi- This paper builds on the findings in Furlong et al. (), day period. which is believed to be the first paper to show that worms Experiment 2 was a continuation of Experiment 1, the are able to efficiently digest and thrive on fresh human modular boxes being rearranged to the configuration in Fur- faeces in a wet (flushing) vermifilter (a filter containing long et al. (), and the effect of hydraulic loading was worms). Two laboratory studies are described which explore assessed (Table 1). Each vermifilter was fed the same critical design parameters. These studies led to the develop- amount, but this amount varied daily. ment and testing of the first full-scale prototype. Finally, the results of the first six months of a field trial of the Tiger CAT prototype Toilet (a vermifilter paired with a pour-flush pan and super- structure) in rural India are presented. A full-scale prototype was based at the Centre for Alterna- tive Technology (CAT) in Wales. It was a cylindrical tank with a diameter of 1.2 m and a height of 1.2 m. Internally METHODOLOGY there was a 65 cm deep drainage layer (material as in Fur- long et al. ), and on top of this was a 10 cm bedding The species of worms used in the laboratory experiments layer (as in the laboratory experiments), which was con- and the first prototype were Eisenia fetida, but the close rela- tained by metal mesh. At the bottom there was a tap, so tive Eisenia andrei were used in the field trials in India, due effluent samples could be taken. The prototype vermifilter to availability. A worm density of 2 kg/m2 was used in all had an insulated lid and was temperature controlled at systems described in this paper. 20 W C by a heating blanket (to simulate a warmer climate). The vermifilter was plumbed to a pour-flush system (two Laboratory experiments litres per flush) and ten users were designated to use the system. Samples for influent and effluent were taken A detailed description of the laboratory scale vermifilter approximately weekly. components can be found in Furlong et al. (). Exper- iment 1 explored the effect of vermifilter configuration on Indian field trials the processing of waste and effluent quality, the effect of lower worm density and feed distribution. The vermifilter The field trials in India were located in a rural village configuration varied from Furlong et al. () as follows: approximately 60 km from Pune, in Maharashtra State. Vermifilter 1 (V1) consisted of a bedding layer and sump Ten households (56 people) were recruited for this trial. only. Vermifilter 2 (V2) consisted of a bedding layer, two Ten vermifilters were constructed in brick, diameter drainage layers and a sump. Vermifilter 3 (V3) consisted of 1.2 m by 1.25 m deep with an open base. The bedding a bedding layer, a drainage layer, another bedding layer layer consisted of 10 cm of local compost and the drainage and a sump. Vermifilter 4 (V4) consisted of a bedding layer (60 cm deep) was graded aggregate, the top layer layer, drainage layer and a sump (Figure 1). being sand. The design incorporated an inspection chamber The bedding material used in all vermifilters was a volu- for influent collection and a vertical perforated pipe for metric mixture of 33.3% coir, 33.3% woodchip and 33.3% effluent collection. The vermifilters were set in the ground vermicompost, and the drainage layer material was as and the effluent infiltrated into the soil.

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Figure 1 | Experiment 1: vermifilter configuration.

Table 1 | Details of Experiments 1 and 2

Experiment 1 (186 days) Experiment 2 (123 days)

Mean faeces Mean faeces Final worm Phase Period Hydraulic addition (g/ Hydraulic addition (g/ Final vermicompost density (kg/ Phase description (days) loading (l/day) day) Vermifilter loading (l/day) day) weight (kg) m2)

1 50 g feed 1–30 12 45 ± 15 1 30 157 ± 45 3.2 11.8 2 100 g feed 31–47 12 97 ± 1 2 12 157 ± 46 3.9 11.3 3 Resting 48–71 1 0 3 1 155 ± 46 3.9 8.3 phase 4 Variable 72–186 12 99 ± 66 4 0 158 ± 46 1.9 8.0 phase

Note: All masses are expressed as wet weights.

All vermifilters were monitored weekly using structured blocking the outlet of the inspection chamber for 24 hours. observations, then five representative vermifilters were moni- The sample was then homogenised. Monthly effluent samples tored monthly. Influent samples were taken monthly by were collected via the perforated sample pipe (1.10 m × 10 cm

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diameter), open at both ends. A collection vessel was placed at Statistical analysis of results was carried out using SPSS the bottom of the pipe to block infiltration into the ground for 12.0.1. One-way ANOVA was used to compare multiple 1 week. The effluent sample was allowed to settle before the data sets using the post-hoc Tukey test. The null hypothesis supernatant was decanted for analysis due to vermicompost of these tests was accepted if p 0.05. being washed into the sample pipe. This ensured the samples collected were representative of the effluent which was being infiltrated into the soil. RESULTS AND DISCUSSION

fi Methods of analysis The process from laboratory to eld took approximately three years.

In the laboratory experiments, wet mass measurements and calculations were performed as previously (Furlong Laboratory experiment 1 et al. ). Influent and effluent samples were taken approximately weekly from the laboratory experiments The total reduction in wet mass of faeces achieved over the and the CAT prototype. These were analysed for chemical course of Experiment 1 (cumulative faecal reduction) was oxygen demand (COD) and thermotolerant coliforms 84–88% (Table 2). No significant difference was found in (TTC) as in Furlong et al. (). The samples from the faecal reduction across the vermifilters. No effect of distri- Indian prototypes were analysed in a commercial labora- buting the waste across the surface of the vermifilter was tory for COD (5220D, APHA (American Public Health found, so a dispersal system is not required. Association) ) and TTC (9222B, APHA (American The weekly faecal mass reduction in V4 (worm density of Public Health Association) )). 2 kg/m2) was compared to that from a vermifilter containing

Table 2 | Results from different vermifilter studies including; COD and TTC reduction, cumulative faecal reduction and bioconversion ratios

Mean across all vermifilters and phases Cumulative faecal Conversion COD TCC reductiona (%) ratiob Effluent Reduction Influent (CFU/ Effluent (CFU/ Reduction Experiment Influent (mg/L) (mg/L) (%) 100 mL) 100 mL) (%)

c 9 6 Furlong et al. 4,666 ± 602 ± 326 87 1.03 × 10 ± 2.13 × 10 ± 2-log10 97–100 1:0.10–0.18 (), (360 days) 2,848 (n ¼ (n ¼ 144) 1.01 × 109 6.12 × 106 35) (n ¼ 18) (n ¼ 72) c 9 6 Experiment 1 6,000 ± 456 ± 283 88 1.02 × 10 ± 1.23 × 10 ± 3-log10 84–88 – (186 days) 8,032 (n ¼ (n ¼ 68) 1.08 × 109 1.71 × 106 17) (n ¼ 9) (n ¼ 36) c,d 8 6 Experiment 2 5,492 ± 719 ± 363 90 9.02 × 10 ± 1.48 × 10 ± 3-log10 80–83 1:0.09–0.19 (123 days) 5,358 (n ¼ (n ¼ 49) 1.31 × 109 1.48 × 106 13) (n ¼ 10) (n ¼ 38) c 8 6 CAT prototype 14,985 ± 830 ± 325 94 8.12 × 10 ± 1.84 × 10 ± 3-log10 –– (210 days) 2,315 (n ¼ (n ¼ 20) 9.90 × 108 1.98 × 106 9) (n ¼ 5) (n ¼ 17) 5 3 Field systems 309 ± 87 167 ± 63 44 5.97 × 10 ± 1.70 × 10 ± 2-log10 98–100 – (180 days) (n ¼ 23) (n ¼ 9) 2.22 × 105 6.02 × 102 (n ¼ 9) (n ¼ 9)

aReduction in the total wet mass of faeces that was added over the course of the experiment (Furlong et al. 2014). bTotal kg of faeces added: kg vermicompost harvested at the end of the experiment (Furlong et al. 2014). cInfluent was a suspension of the average daily mass of faeces over a week suspended in 12 L of water. dOnly one concentration of influent was analysed.

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the same bedding material from Furlong et al. (), which this would cover the system to a depth of 21.6 cm. The actual had a higher worm density (4 kg/m2). A difference was faecal accumulation over six months was estimated (by obser- found until week 5, then the impact of using a lower worm vations of coverage and depth of faeces) to be between 0.2 and density decreased. Suggesting a worm density of 2 kg/m2 4.5 kg (mean 1.5 kg). In four of the toilets it was 1 kg, which could be used as long as the lag phase (4–5 weeks) was engin- shows that the worms were processing daily the amount of eered into the system. No significant difference was found in faeces entering the vermifilters. the COD or TTC reduction across all the vermifilters. This Vermicompost started to accumulate within 2 weeks of suggests that treatment of effluent was through the separation use, which was quicker than in the laboratory experiments of faecal matter by the bedding layer, rather than through and the CAT prototype. This was thought to be because of treatment in the subsequent layers. the higher temperatures in the India prototypes (20 to 41 W C), which hastens the worms’ metabolism. The vermi- Laboratory experiment 2 compost accumulated around the edge of the faeces and was then pushed to the sides of the vermifilters. This No significant difference in effluent quality or the processing of means that the users will be able to empty the system rela- faeces was found across the vermifilters. This suggests that the tively easily. Over the six month period a depth of worms are able to process faeces under both wet and dry con- between <1 and 3 cm of vermicompost accumulated, ditions. Mass reduction under drier conditions may include the which means the vermifilters will only require emptying effects of drying of faecal material as well as processing by the after five years. The worms themselves were found to be elu- worms. When the vermifilters were decommissioned, the ver- sive and were only seen in two of the vermifilters. This is micompost produced ranged from 1.9 to 3.9 kg (Table 1). The quite normal as worms feed from beneath. A lack of lowest production was in V4 which supports this interpret- accumulation of faeces together with the build-up of vermi- ation. V4 contained more flies, the surface of the faeces was compost indicates that the worms are present and covered in fungus and it smelt anaerobic. The worm densities processing faeces. at the end of this experiment can be seen in Table 1. Higher The reduction of COD and TTC was lower in the Indian final worm densities were associated with higher hydraulic prototypes compared to the CAT prototype (Table 2). This loading, supporting the theory that E. fetida prefer wetter was due to lower levels in the influent of the vermifilters environments (Furlong et al. ). in India (Table 2). When this was explored it was found that up to 15 litres of water was being used per person per CAT prototype day to flush the systems in India compared to only five litres used per person per day at CAT. A comparison of From Table 2 it can be seen that the reduction in COD and the effluent COD and TTC reveals in absolute terms the TTC was comparable with the laboratory experiments. effluent quality from the Indian vermifilters is higher than During the 210 days of monitoring, the system was found for the CAT prototype (Table 2). to work well, with no visible faecal overloading of the vermi- filter. The system was designed for ten users, which was found to equate to two visits for urination only and three CONCLUSIONS for urination and defecation per day, so it could be said that the system was underused. This paper describes the journey of developing a vermifilter as a form of onsite sanitation from laboratory experiment Indian field trials through to field trials. The laboratory experiments honed critical design criteria which were then incorporated into It was estimated that during six months 216 kg of faecal matter the first full-scale prototype. As this functioned as expected, had entered each vermifilter (based on six people producing the process advanced to field trials in rural Indian house- 200 g of faecal matter per day, over six months). If undigested holds. This study shows that the Tiger Toilets (vermifilter

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fl paired with a pour- ush toilet pan and superstructure) have REFERENCES been operating successfully in real-life situations for six

months. The Tiger Toilet has the potential to be superior APHA (American Public Health Association),  Standard to conventional technology as it provides users with the Methods for the Examination of Water and Wastewater. aspirational benefits of a septic tank, a smaller footprint American Public Health Association, Washington, DC, USA. Eastman, B. R., Kane, P. N., Edwards, C. A., Trytek, L., Gunadi, B., and better treatment of waste. Due to the characteristics of Stermer, A. L. & Mobley, J. R.  The effectiveness of the by-product (vermicompost) and where it is deposited vermiculture in human pathogen reduction for USEPA in the system, many of the problems associated with empty- biosolids stabilization. Compost Science & Utilization 9 (1), – ing traditional onsite sanitation systems are also overcome. 38 49. Furlong, C., Templeton, M. R. & Gibson, W. T.  Processing of human faeces by wet vermifiltration for improved on-site sanitation. Journal of Water, Sanitation and Hygiene for Development 4, 231–239. ACKNOWLEDGEMENTS Thye, Y. P., Templeton, M. R. & Ali, M.  A critical review of technologies for pit latrine emptying in developing countries. Critical Reviews in Environmental Science and Technology The authors acknowledge the support of the Bill and 41 (20), 1793–1819. Melinda Gates Foundation through a grant to the London Xing, M., Zhoa, C., Yang, J. & Lv, B.  Feeding behavior and trophic relationship of earthworm and other predators in School of Hygiene and Tropical Medicine and USAID vermifiltration systems for liquid-state sludge stabilization DIV grant number AID-OAA-F-13-00049 awarded to Bear using fatty acid profiles. Bioresource Technology 169, Valley Ventures Ltd. 149–154.

First received 3 May 2015; accepted in revised form 2 November 2015. Available online 26 November 2015

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