suppressing the odor. Study was organized in order to use the vermicompost as
a biofilter media to suppress odor and optimize the thickness of vermicompost to
...
Global Journal of Environmental Research 2 (1): 18-22, 2008 ISSN 1990-925X © IDOSI Publications, 2008
Vermicompost as Biofiltration Media to Control Odor from Human Feces 1
1
Kunwar D. Yadav, 2Vinod Tare and 1M. Mansoor Ahammed
Department of Civil Engineering, SV National Institute of Technology, Surat, Gujarat, India 2 Department of Civil Engineering, Indian Institute of Technology, Kanpur, UP, India
Abstract: There are a number of options to control the odor during the degradation of organic wastes and biofiltration is one of them. Fresh vermicompost has a high surface area, adequate absorption capacity and high diversity and population of micro-organisms. Vermicompost helps in degradation process as well as in suppressing the odor. Study was organized in order to use the vermicompost as a biofilter media to suppress odor and optimize the thickness of vermicompost to remove/degrade the volatile fatty acids (VFA) emission. The 2.5 cm thick vermicompost layer in bedding and covering was found to be sufficient enough to eliminate the odor of system and reduce the Volatile Fatty Acids level from 161.55 to 39.61 mg/g within a period of 21 days. Key words: Odor
Vermicompost
Volatile fatty acids (VFA)
INTRODUCTION
Human feces
[5], treatment of toluene vapours [6] and removal of butyric acid [7]. The vermicompost is much superior compared to compost in bulk density, porosity and particle size. The fresh vermicompost also has a high surface area and a rich diversity of micro-organisms to biodegrade the VFA [8-10]. The main objective of the present study is to use the vermicompost as biofiltration media and to find out the thickness of vermicompost layer that is sufficient to control odor and to reduce the odor causing VFA level. In the present study, it was hypothesized that different thickness of vermicompost on bedding and covering would affect on the odor and VFA level and help in the organic degradation process. It was also hypothesized that within 20-30 days organic matter would partially stabilize and it will not create nuisance to the environment if we provide sufficient amount of fresh microbial culture to the system.
The odor is one of the major issues in safe disposal of human excreta. According to Sato et al. [1], volatile fatty acids (VFA); acetic, propionic and butyric acids are the main malodorous substances in the human waste (about 90%). The physical processes (dilution, physical adsorption, covering and masking), chemical processes (Scrubbing, oxidation and incineration) and biological processes (Biofiltration) have been used in the past to treat the volatile organic compounds and among those biofiltration is the most cost effective and efficient method for controlling the odor [2]. Biofiltration means passing of odor from biological media followed by biodegradation of captured compounds. The odor components are transferred from gas phase to liquid and solid phase of the particles in the filter material [3]. Physical structure (porosity, surface area and density), temperature, moisture content and diversity of micro-organism are all key factors which influence the efficiency of the biofiltration process. Researchers have studied several odor causing gases by using the compost as filtration media for biofiltration process. Compost was used as biofiltration media for control of odor from ammonia gas [3], hydrogen sulfide removal [4], biodegradation of styrene laden waste
MATERIALS AND METHODS Vermicompost: Fresh and mature vermicompost was collected from the stock culture bin. The vermicompost was produced from cow dung by utilizing the earthworm species Eisenia fetida.
Corresponding Author: Kunwar D. Yadav, Department of Civil Engineering, SV National Institute of Technology, Surat, Gujarat, India E-mail:
[email protected]
18
Global J. Environ. Res., 2 (1): 18-22, 2008
control that had 5.0 cm thick human feces.150 g (wet weight) samples were colleted every day by mixing feces layer after scrapping out the covering layer in A, B and C reactor and in rector D directly from feces layer. The samples were analyzed for VFA, pH and moisture content. The moisture in the covering layer was maintained by sprinkling of water to maintain the microbial activity.
Table 1: Physicochemical Characteristics of Fresh feces and Vermicompost S. No
Parameter
Fresh Feces
Vermicompost
1
pH
5.50
7.00
2
Moisture Content, %
78.00
50.00
3
Electrical Conductivity, mmho/cm
42.80
11.70
4
Carbon, % (dry weight)
43.50
20.50
5
Nitrogen, % (dry weight)
3.75
1.78
Methods: The analysis of volatile fatty acids (VFA) was done by titration method as per [11] and pH was determined by digital pH meter (Model No: CL-51, Toshniwal, India).
300 mm
Layer 3
RESULTS AND DISCUSSION
Layer 2 Layer 1
The VFA level in the fresh feces varied from 161.55 to 162.21 mg/g and pH 5.08 to 5.21. VFA level started decreasing from second day of experiment till the end of the experiment i.e. 21 days (Fig. 2). Substantial reduction in VFA level from 162.21 to 60.54 mg/g of feces in reactor-A was observed as compared to 162.21 to 97.22 mg/g (Fig. 2) in reactor-B with application of a thick (5.0 cm) double vermicompost layer. It was found that the efficiency of VFA reduction in reactor-A was low as compared to that of reactor-C (VFA decreased from 161.55 to 39.61 mg/g of feces), where the feces were actually situated between the two layers of the vermicompost. Therefore, it can be inferred that the application of vermicompost bed enhanced the loss of VFA from the system. All reactors showed in greater removal ranging from 40.07 to 75.49% in VFA as compared to the control bin i.e. reactor-D (feces only), which points towards the fact that vermicompost significantly enhances the decrease of VFA from feces during the processing. Vermicompost helps by increasing the pH and in the degradation of volatile fatty acids by absorbing and degrading the malodorous volatile organic compounds which are generated from human feces and reduces the odor.
450 mm
300 mm
Fig. 1: Schematic Representation of Reactors Different Layer of Materials
and
Feces: Fresh human feces were collected from a nonflush, drop and store type of toilet from a village near IIT Kanpur, named Mandhana. The toilet was designed to have separate seats for defecation and anal cleaning. Feces from 4 different houses of approximately 16-20 persons using the toilet were collected daily and thoroughly mixed before using it. Some chemical and physico-chemical characteristics of material are given in Table1. Four sets of reactors made of GI sheet were used as depicted by the schematic diagram shown in Fig. 1 and configuration details in Table 2. It was operated for 21 days and 4.5 kg of fresh feces ( wet weight) were fed in all the reactors. The first and second reactors were covered with 2.5 cm and 5.0 cm thick vermicompost layers respectively, having moisture content of 50%. In third reactor, 2.5 cm thick bedding and covering of vermicompost was provided. The fourth reactor served as
Table 2: Configuration Details of Reactors and Materials (Vermicompost, Feces) Filled in the Different Layer with Variable Thicknesses Layer 1
Layer 2
Layer 3
-----------------------------------------------------
--------------------------------------------------------
------------------------------------------------
Reactors
Material
Material
Material
A
Feces
B
Feces
C
Vermicompost
D
Feces
5.0
Thickness (cm) 5.0
Thickness (cm)
Thickness (cm)
Vermicompost
2.5
-
5.0
Vermicompost
5.0
-
-
2.5
Feces
5.0
Vermicompost
2.5
-
-
-
-
19
-
Global J. Environ. Res., 2 (1): 18-22, 2008
160
Reactor A: Feces with 2.5 cm vermicompost covering
7.2
140 120
6.8
100
6.4
80
6.0
60 40
5.6
20
5.2
0 160
Reactor B: Feces with 5.0 cm vermicompost covering
7.6
140
7.2
120
6.8
100 80
6.4
60
6.0
40
5.6
20 0 160
5.2 Reactor C: Feces with 2.5 cm vermicompost bedding and covering
7.6
140
7.2
120
6.8
100 80
6.4
60
6.0
40
5.6
20 0 160
5.2 Reactor D: Feces only
7.6
140
7.2
120
6.8
100 80
6.4
60
6.0
40
5.6
20 0
5.2 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Duration, days pH
VFA (Volatile Fatty Acids) Fig. 2: Temporal Variation in VFA and pH with or without Vermicompost Layer
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Global J. Environ. Res., 2 (1): 18-22, 2008 Table 3: Qualitative Measurement of Odor in all Reactors by a Group of Students
Days
Reactor A
Reactor B
Reactor C
Reactor D
--------------------------------
--------------------------------
---------------------------------
----------------------------------
System
System
System
System
Feces
1
-
2
-
3
-
4
Feces
Feces
-
-
5
-
-
-
6
-
-
-
7
-
-
-
8
-
-
-
9
-
-
-
10
-
-
-
11
-
-
-
12
-
-
-
13
-
-
-
14
-
-
-
15
-
-
-
16
-
-
-
17
-
-
-
18
-
-
-
19
-
-
-
-
20
-
-
-
-
21
-
-
-
-
Odor Level: - Nil,
Mild,
Moderate,
High,
Feces
Offensive
The reduction in the odor and volatile fatty acid emission was due to vermicompost characteristics (high population and diversity of microbial organisms, high surface area and good bulking agent) as compared to the control reactor. The pH increased from 5.21 to 6.81, 5.21 to 6.87 and 5.15 to 7.34 in reactors-A, B and C respectively (Fig. 2). It indicates that the thickness of vermicompost layer inversely affects the increase of pH and addition of vermicompost bed enhances the pH to normal or neutral level. In control reactor, the pH increment was 1.35 (i.e. 5.08 to 6.43) which is comparatively lower compared to pH increment in other reactors (1.60, 1.66 and 2.19 for reactor A, B and C respectively) using vermicompost layer. Vissar and Postma, [12]; Kay, [13]; suggested that microbial oxidation of VFA could cause the increase in pH of the medium and vermicompost will increase the microbial activity in the waste. This further strengthens our observation that vermicompost has played a significant role in raising the pH. The qualitative analysis of odor was also done for all reactors every day in a reactor as a system and in the feces layer (Table 3). The reactor –A and C have a mild odor up to 4 days in the system. Initially, for 3-4 days volatile acids production was high and so a few cracks were developed in the covering layer and create the mild
odor. The reactor-B system has a no odor in the system from first day (Table 3). Odor level in the feces layer was depending on the degradation in the organics. The reactor-D has an offensive odor for the first one week and after that high odor up to end of the experiment and it was due to absence of vermicompost layer. CONCLUSION Vermicompost cover with a thickness of 2.5 cm seems to be the optimum configuration for a significant reduction of odor and use as biofiltration media. Application of fresh vermicompost as bedding and covering (Sandwich model) seems as an attractive method to reduce odor and volatile fatty acids concentration and to maintain the pH. REFERENCES 1.
2.
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Sato, H., T. Hirose, T. Kimura, Y. Moriyama and Nakashima, Y, 2001. Analysis of malodorous volatile substances of human waste: Feces and Urine. Journal of Health Science, 47(5): 483-490. Schlegelmilch, M., J. Streese and R. Stegmann, 2005. Odour managment and treatment technologies: An overview. Waste Management, 25: 928-939.
Global J. Environ. Res., 2 (1): 18-22, 2008
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Hong, J.H. and K.J. Park, 2005. Compost biofiltration of ammonia gas from bin composting. Bioresource Technology, 96: 741-745. Sagastume, J.M. and A. Noyola, 2006. Hydrogen sulfide removal by compost biofiltration: Effect of mixing the filter media on operational factors Bioresource Technology, 97: 1546-1553. Dehghanzadeh, R., A. Torkian, B. Bina, H. Poormoghaddas and A. Kalantary, 2005. Biodegradation of styrene laden waste gas stream using a compost-based biofilter. Chemosphere, 60: 434-439. Rene, R.E., D.V.S. Murthy and T. Swaminathan, 2005. Performance evaluation of a compost biofilter treating toluene vapours. Process Biochemistry, 40: 2771-2779. Otten, L., M.T. Afzal and D.M. Mainville, 2004. Biofiltration of odours: laboratory studies using butyric acid. Advances in Environmental Research, 8: 397-409. Satchell, J.E., 1983. Earthworm ecology in forest soil. In Earthworm Ecology: from Darwin to Vermiculture.(J.E. Satchell Ed.), 161-170, Chapman &Hall, London.
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Mulongoy, K., 1986. Microbial biomass and maize nitrogen uptake a Psophocarpus palustris live mulch grown on a tropical Alfisol. Soil Biology and Biochemistry, 21: 395-398. Mulongoy, K. and A. Bedoret, 1989. Properties of worm cast and surface soils under various plant covers in the humid tropics. Soil Biology and Biochemistry, 21: 197-203. Buchauer, K., 1998. Comparison of two simple titration procedure to determine volatile fatty acids in influents to waste-water and sludge treatment processes. Water SA, 24(1): 49-56. Visser, A.S. and P.W. Postma, 1973. Permeability of Azotobacter vinelandii to cations and anions. Biochim. Biophys. Acta, 298: 333-340. Kay, W.W., 1978. Transport of carboxylic acids. In Bacterial Transport, ed B.P. Rosen. Marcel Dekker, New York, pp: 385-411.
