IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Research article
erd

Reuse of Wastewater from Cassava Industry for Napier GrassProduction
CHULEEMAS BOONTHAI IWAI*
Integrated Water Resource Management Research and Development Center in NortheastThailand,Khon Kaen University, Khon Kaen, Thailand
E-mail: chuleemas1@gmail.com; chulee_b@kku.ac.th

MONGKON TA-OUN
Faculty of Agriculture, Khon Kean University, Khon Kean, Thailand

BARRY NOLLER
The University of Queensland, Centre for Mined Land Rehabilitation (CMLR), Sustainable Minerals
Institute, Brisbane, Australia
Received 23 February 2015

Accepted 15 May 2015(*Corresponding Author)

Abstract Cassava industry plays an important socio-economic role in Thailand economy. The
growth of the cassava processing industry has resulted in extensive water pollution, as it
generates large amounts of wastewater with extremely high concentrations of organic pollutantsfrom washing and extraction. The need for wastewater management from cassava processing
was apparent and fit with green technology for reuse of wastewater for agriculture. Napier grass(Pennisetum purpueum), a perennial species, has become a priority source of biomass foralternative energy production in Thailand, as the National Energy Policy Council has raised thetarget of power production from Napier Grass to 3,000 MW under the 10-year alternative
energy development plan (2012-2021) for Thailand. This study aimed to investigate thefeasibility of using Napier Grass cultivation from cassava industry wastewater. Wastewater
quality (effluent and influent) from cassava industry and its impact on soil chemical properties
were studied at a site in Kalasin province, northeast Thailand to observe the effects of different
concentrations (0%, 25, 50%, 75% dna 100%) on germination test and Napier Grass biomass
production. The wastewater characteristics were: pH of 7.2, EC 4 dSm-1, BOD 119 mgL-1, COD
1070 mgL-1, TS 3230 mg L-1, TKN 207 mg L-1, TP 226 mgL-1 and water soluble K 1490 mgL-1.
The soil exposed to wastewater gave higher EC, more organic matter accumulation, higher total
N, and available P when compared to soil without being exposed to cassava wastewater. Theresults showed that the wastewater concentrations significantly increased the Napier grassbiomass. Therefore, wastewater from cassava industry can be used in Napier grass production
as an example of application of green technology.
Keywords cassava production, wastewater quality, soil property, Napier grass biomass
production

INTRODUCTION
Reuse wastewater in agriculture is gaining wider acceptance worldwide. It represents an agronomic
option that is increasingly being investigated and taken up in regions with water scarcity, growing
urban populations, and rising demand for irrigation water (Gatta et al., 2014; Meli et al., 2002; FAO,
2011). Many irrigated areas around the world are experiencing water shortages due to several factors,including climate change, and surface and groundwater pollution. Water scarcity poses serious
economic, social, and even political concerns in all of its aspects. Under these circumstances, reuse ofⒸISERD

42

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

wastewater can help to mitigate the damaging effects of local water deficits (Gatta et al., 2014; FAO,2010). Treated wastewater not only offers an alternative irrigation source, but also the opportunity torecycle plant nutrients (Chen et al., 2008). Its application might ensure the transfer of fertilizing
elements, such as nitrogen (N), phosphorous (P), potassium (K+), organic matter, and nutrients, into
agricultural soil (Gatta et al., 2014). The cassava processing industry is considered to be one of thelargest food processing industries in Thailand. However, the growth of the cassava industry has
resulted in serious environmental pollution as it generates large amount of solid waste and wastewaterwith high organic content (Chavalparit and Ongwandee, 2008).
Together with the rice and sugarcane industries, the tapioca starch-processing industry has played
an important role in Thailand’s agricultural economy. Known as the world’s largest producer andexporter of tapioca starch, Thailand produced over seven million tons of starch in 2004. Approximate
annual revenue from tapioca starch export was 38,805 million baht or 1,060 million dollars (DOA,2005). Tapioca is produced from treated and dried cassava (manioc) root and used in the food, paper,and toothpaste industries. Only 20% of the cassava root harvested in Thailand is delivered to starchprocessing plants while the rest is used in the production of pellets and chips. Currently, Thailand has
92 tapioca processing plants with a total production capacity of native and modified starch at about
16,910 and 4350 ton/day, respectively (DOA, 2005). Normally, these tapioca-processing plants operate
24 hours per day from September to May each year.
The production of native starch from cassava root involves seven major stages. These are root
washing, chopping and grinding, fibrous residue separation, dewatering and protein separation,dehydration, drying, and packaging. The production facilities experience a number of environmental
problems such as the consumption of large volumes of water and energy, and the generation of highorganic-loaded wastewater and solid waste. The starch extraction process requires a vast volume ofwater, which in turn produces large amount of wastewater. According to the study of Tanticharoen andBhumiratanatries (1995), the production of one ton of starch from cassava generates an average of 20
m3 of wastewater. Hien et al. (1999) reported the characteristics of wastewater from Vietnamese
tapioca starch plants with values of 11,000-13,500 mg CODL-1, 4200-7600 mg SSL-1, and pH of 4.55.0. The approximate generation of wastewater and solid waste (fibrous residue and peel) from one tonof starch was 12 m3 and 3 kg, respectively (Hien et al., 1999).
Thus appropriate wastewater management from cassava starch industry is needed. Reuse of such
wastewater and its nutrients for agriculture fits with green technology. An appropriate class to consider
for nutrient uptake is grass with high biomass. Pennisetum purpureum (Napier grass) is also known aselephant grass or Ugandan grass and is a species of perennial tropical grass native to the Africangrasslands and is cultivated extensively. Napier grass (P. purpueum) is a perennial plant that is also apriority source of biomass for alternative energy production in Thailand. The National Energy Policy
Council, in its 10-year alternative energy development plan (2012-2021), has set a target to produce
3,000 MW of electricity from Napier grass. Napier grass has low water and nutrient requirements,
therefore it can make use of uncultivated lands. Historically, this species has been used primarily forgrazing. Recently, however, it has been incorporated into a pest management strategy. In addition tothis role, Napier grass improves soil fertilityand protect arid land from soil erosion. They are alsoutilized for firebreaks, windbreaks, in paper pulp production and most recently to produce bio-oil,biogas and charcoal.
The perennial Pennisetum purpureum Schumach (Napier or elephant grass) readily crosses withthe annual Pennisetum americanum (L.) Leeke (pearl millet) and the resultant interspecific hybrids are
more vigorous than the parent species. Hence, several hybrid Napier grass cultivars (P. purpureum andP. americanum) have been developed (Premaratne and Premalal, 2006). Because of the high biomass
production and very high forage quality for livestock, growth of these hybrids is widely promoted in
subtropical and tropical countries including Thailand (Tudsri et al., 2002; Premaratne and Premalal,2006). Recently, a very productive cultivar (Pakchong1) of this hybrid grass has been developed andmarketed by Thailand’s Department of Livestock Development. The Pakchong1 cultivar is claimed toⒸISERD43

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

have several advantages over other Napier grass cultivars, as it grows taller, has a higher content ofcrude protein, has an annual yield exceeding 500 ty-1, and can be harvested 5-6 times per year
(Jampeethong et al., 2014).
The nutrients wastewater from the cassava industry has the potential to contribute to crop
production, including that of Napier grass. Nevertheless, there is a need for periodic monitoring, toavoid any imbalance in the nutrient supplies, which might cause an imbalance; such wastewater canalso be a source of pathogenic organisms, enteric bacteria and viruses and potentially hazardous
chemical substances such as salts, heavy metals, and surfactants. Hence, there is the need for furtherstudies to investigate the feasibility of using wastewater from cassava industry for Napier grass
production.
OBJECTIVES
The objectives of the study were: (i) to evaluate the effects of nutrients in the wastewater from cassava
industry on qualitative and quantitative aspects of Napier grass production; and (ii) to assess the impactof the wastewaters on the soil properties.
METHODOLOGY
Water and Soil SamplingThree samples of the wastewater from influent and effluent from biogas system at cassava industry
were collected in sterile 1000-mL glass bottles, and transported to the laboratory in refrigerated bags.
The samples collected were kept in a refrigerator at +4◦C, and examined within 24 hours of theircollection. Soil samples were collected in triplicate from each of 5 treatments before and after. All ofthe soil samples were taken from a 15-cm layer in each plot, from under the drippers, and they wereair-dried, crushed, and passed through a 2 mm sieve before the chemical analysis.
Water Quality Analysis
The water samples were analyzed in triplicate, according to the international standard methods(APHA-AWWA-EF, 2005). The analysis included the physico-chemical parameters of pH, electricalconductivity (ECw; dSm−1), total solids (TS; mgL−1), biological oxygen demand over 5 days (BOD5;mgL−1), chemical oxygen demand (COD; mgL−1), Total Kjeldahl Nitrogen (TKN), Total Phosphorus(TP; mg L−1) and potassium (K+; mgL−1).
Soil Chemical Analysis
The soil electrical conductivity and pH were measured ion 1:2 (w/v) and 1:2.5 (w/v) aqueous soil
extracts, respectively. The pH and EC were measured using a digital pH meter in 1/2.5 (w/v) deionizedwater. Total N (total nitrogen) was measured by the micro Kjeldahl method (Jackson, 1973; Bremnerand Mlvaney, 1982). Exchangeable phosphorous (Exch. P) was determined by using the Bray II
extraction method (Schroth et al., 2003) and Exchangeable Potassium (Exch. K) was determined by 1
N Ammonium acetate and Flame photometry method.

ⒸISERD44

IJERD – International Journal of Environmental and Rural Development (2015) 6-2Plant Growth Test
An experiment was carried out to investigate the effects of wastewater from cassava industry on
germination and plant growth under greenhouse conditions at Khon Kaen University, Thailand, at(latitude of 16° 28' N and longitude of 102° 48' E) during the rainy season of 2014.
Napier grass plants were used in this experiment. The experiment was laid out in a completely
randomized design (CRD) with three replications for each crop. Five-wastewater concentration
treatments were used (T1: tap water only, T2: 25% wastewater concentration, T3: 50% wastewater
concentration, T4: 75% wastewater concentration, and T5: 100% wastewater concentration) were used.
For five kilograms of 2 mm sieved air-dried of each soil sample were placed in each black plastic potsof 30 cm height and 25 cm diameter for each treatment. Wastewater was applied before planting inevery three days until termination. Bud per stem, height, fresh weight, dry weight, yield of stem androot were recorded.
Statistical Analysis
The data obtained from different experiments were analyzed by using the one-way analysis of variance(ANOVA) function of Statistica 8 software (Version 8, USA) to test for variations (p<0.05) that weredeemed significant between treatment groups and controls.
RESULTS AND DISCUSSION
The wastewater released from cassava industry characteristics were pH of 3.9, 7.2, EC of 1.5, 4.0
mS/cm, BOD of 633, 119 mg/l, COD of 4267, 1067 mg/l, TS of 4853, 3227 mg/l, TKN of 28, 207 mg/l,
TP of 120, 226 mg/l and water soluble K of 1833, 4900 mg/l, respectively (Table 1). The result
suggests that nutrients were high in wastewater. Therefore, it could be use for grass nutrient uptake.
Table 2 shows the effects of wastewater from cassava industry on soil properties. In the soil
exposed to wastewater, the pH of the soil increased compared to the soil without exposure towastewater. Similarly, the application of wastewater resulted in higher EC, N, P, K than the soil
without exposed to wastewater. The exposed soil contained more organic matter accumulation andhigher exchangeable K than the soil without exposure to wastewater. The noticeable increase ofexchangeable K in the soil exposed to wastewater might be explained by the presence of high levels oforganic matter in it. The soil exposed to wastewater had the higher total N content, whereas the soil
without being exposed to wastewater had low value. The high total N content in soil by exposing towastewater might be due to the fact that wastewater might enhance salt uptake and immobilization ofN. The application of wastewater resulted in higher available P than the soil without exposed towastewater. It might be due to the fact that the wastewater resulted in increasing available P in thesurface layer. The soil exposed to wastewater gave higher exchangeable K + when compared to the soil
without being exposed to wastewater. This might be the initial high content of these elements in thewastewater. Therefore, the results of this study show that soil chemical properties after being treatedwastewater from cassava were better than the ones without application of wastewater.
Plant Growth Experiment
The biomass yields of the Napier grass plants grown on the amended soils have been determined using
their height and weight data for plant stem and root biomass. The biomass of the Napier grass plants
increased in the treatment using wastewater for all the samples. The highest yields were recorded for
wastewater at 25% concentration (Tables 3 and 4).

ⒸISERD45

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

Table 1 The wastewater from cassava industry characteristics
Wastewater
Parameter (unit)
pHEC (dSm-1)
BOD (mgL-1)
COD (mg L-1)
TS (mg L-1)
Total N (mg L-1)
Total P (mg L-1)
Total K (mg L-1)

Influent
3.9
1.5
633
4270
4850
28120
1830

Effluent

Water quality standard for effluent discharge(MOST, 1996)

7.2
4.0
119
1070
3230
210
226
4900

5.5-9.060400
100-200-Table 2 Soil quality after apply wastewater from cassava industry
pHEC (dSm-1)

ytil uqdlioS
TN (%)

Exchangeable
P (ppm)Exchangeable
K (ppm)Before6.12b0.038c0.008c34b44crotf
6.01c
0.091a0.021b48a64b)inrlqtno)
6.44a
0.065b
0.028a43a92arotf)trrlqtno)
F-test
**
**
**
*
**
CV (%)
0.45
3.12
8.04
5.18
2.79
Note: Mean (n=3) in the same column followed by the same lower case letters are not significantly different at p≤0.05

Table 3 The effects of wastewater from cassava industry (influent) on Napier grass production
Treatment
Buds/ stem
HeightStem fresh
Stem dry
Root fresh
Root drywastewater(cm)
biomass(g)biomass
biomass
biomass
concentration
(g)
(g)
(g)
0 %(Control)
2.67
64.33
19.86b
2.35 b
2.71c
0.31b
ab
ab
b25%
3.67
72.68
43.30
3.67
7.09
0.50ab
abab
ab
50%
4.33
77.00
50.87
4.09
8.02
0.72ab
75%
4.33
76.33
43.70ab2.22 b
7.00b0.28 baaa
100%
3.33
78.667
71.67
4.75
11.58
0.76 aF-test
nsns
**
***
**
C.V. (%)
26.35
13.02
26.87
21.40
30.72
22.23
Note: Mean (n=3) in the same column followed by the same lower case letters are not significantly different at p≤0.05

Table 4 The effects of wastewater from cassava industry (effluent) on Napier grass production
Stem dry
Root dryTreatment
No.
HeightStem fresh
Root fresh
biomass
biomass
wastewater
Bud/(cm)biomass
biomass(g)(g)
concentration
stem
(g)
(g)
0 %(Control)
2.676
4.33
19.86
2.35
2.71
0.31
25%
3.67
76.33
35.26
2.87
5.47
0.38
50%
3.00
70.68
37.11
3.19
5.70
0.51
75%
2.67
72.33
33.39
2.60
5.44
0.39
100%
2.67
64.68
23.06
1.60
3.04
0.14
F-testnsnsnsnsnsnsC.V. )%)
35.21
12.46
41.93
35.62
44.49
62.27
Note: Mean (n=3) in the same column followed by the same lower case letters are not significantly different at p≤0.05ⒸISERD46

IJERD – International Journal of Environmental and Rural Development (2015) 6-2

CONCLUSION
Every wastewater application significantly produced maximum Napier grass biomass based on
measured data. Therefore, wastewater from cassava industry natural can be reused to give enhanced
Napier grass biomass production. The reuse of wastewater from cassava industry for Napier grass
production considered the aspects of water reuse, nutrient reuse, and biomass production. The highbiomass yield of Napier grass also makes it a possible potential feedstock in producing cellulosic
ethanol, with the added benefit of water quality improvement and sustainable energy. This study
suggests that through the cultivation of highly productive, low input, perennial and valuable plant
species, benefits can be realized in the form of water quality improvement, water reuse, nutrient reuse,biomass production, and sustainable energy.
ACKNOWLEDGEMENTS
This research project was supported by Integrated Water Resource Management Research andDevelopment Center in Northeast Thailand, Khon Kaen University, Thailand. We would like to thankKalasin cassava industry, Miss Matanee Polsuwan, Miss Arpaporn Mudnawed, and Mr. Thongchai
Seangchad for research assistance.
REFERENCES
Chavalparit, O. and Ongwandee, M. 2009. Clean technology for the tapioca starch industry in Thailand. Journalof Cleaner Production, 17, 105-110.
DOA. 2005. Database of agriculture: starch. Thailand: Department of Agriculture, Ministry of Agriculture andCooperatives. Available in: http//www.doa.go.th/data-doa/starch/stat/st04.htm.
Gattaa, G., Libuttia, A., Gagliardia, A., Beneducea, L., Brusettib, L. Borrusob, L., Disciglioa, G., and Tarantinoa,E. 2015. Treated agro-industrial wastewater irrigation of tomato crop: Effects on qualitative / quantitative
characteristics of production and microbiological properties of the soil. Agricultural Water Management, 149,33-43.
Hien, P.G., Oanh, L.T.K., Viet, N.T., and Lettinga, G. 1999. Closed wastewater system in the tapioca industry inVietnam. Water Sci Technol, 39, 89-96.
Ministry of Science, Technology and Environment (MOST). 1996. Water quality standard: Issued under theEnhancement and Conservation of the National Environmental Quality Act B.E.2535 (1992), published inthe Royal Government Gazette, Vol. 113 Part 13 D, dated February 13, B.E.2539.
Tanticharoen, M. and Bhumiratanatries, S. 1995. Wastewater treatment in agro-industry: A case study inThailand. In: Sastry, C.A., Hashim, M.A., Agamuthu, P. editors. Waste treatment plants. John Wiley & Sons
(Asia).

ⒸISERD47