Hontonho E. J. Deguenon, Martin P. Aina, Akuemaho V. O. Akowanou, and Dominique C. K. Sohounhloue. From the institute of Benin. wrote a research paper about, Plants Powering Cleaner Wastewater: Reed Bed Treatment. Entitled, Purifying performances of different plants in domestic waste water treatment with reed beds. This research paper published by the International Journal of Biosciences | IJB. an open access scholarly research journal on Biosciences, under the affiliation of the International Network For Natural Sciences | INNSpub, an open access multidisciplinary research journal publisher.
Abstract
The rejection of untreated waste water in the nature decreases groundwater quality. Waste water treatment plants like activated sludge plant and stabilization pond plant built in Benin show their limits. Due to these problems, reed beds have to be experimented to bring a durable solution to waste water treatment problems in Benin. Compare to activated sludge plant and to stabilization pond plant, reed beds are the cheapest based on the technical and economical point of view. On addition to that, reed beds are easy to build and to maintain. The experiment plant is composed of four basins. The first basin is unplanted. The second basin is planted with Echinochloa pyramidalis. The third basin is planted with Panicum maximum and the last basin is planted with Typha domingensis. Each basin is a 1 m3 tank with drilled drain pipes. Three differentl ayers of gravel have been put on drilled drain pipes. Treated water analysis showed that the Typha domingensis basin has the best purfiying performances with final concentrations : 0 mg/L ; 21,10 mg/L ; 10 mg/L ; 0 mg/L et 12,20 mg/L respectively for TSS, COD, BOD5, TKN and TP. These final concentrations reached the discharge standards for municipal wastewater treatment plant in Benin. Consequently, Typha domingensis beds can be popularized by the beninese government to solve waste water treatment problems.
Introduction
In Benin, available
fresh water is more and more polluted by domestic waste water. This pollution
decreases groundwater quality and leads to hydric diseases. This pollution also
increases the drinking water price. Hydric diseases in volve thousand children
deaths each year in Benin. In Benin, poor people consume polluted water without
treatment. According to Kivaisi, reed bed plant is a cheaper waste water
treatment process based on technical and economical point of view. On addition
to that reed beds can be used to solve waste water treatment problems in
developing countries like Benin (Kivaisi, 2001). Moreover, reed beds are easy
to build and to maintain (Denny, 1997; Haberl, 1999; Konnerup et al., 2009).
Hounkpe demonstated that the domestic waste water management in Benin is very
critical. Benin has only three waste water treatment plants to treat waste
water conveyed by emptying trucks. There are a waste water treatment plant in
Ekpe, PortoNovo and Parakou. Sadly these waste water treatment plants show
their limits (Hounkpe, 2014). Due to all these problems, reed beds have to be
experimented to bring a durable solution to waste water treatment problems in
Benin (Aina et al., 2012). Benin is a developing country. So reed bed plant is
a new idea to explore in order to treat waste water in Benin. Deguenon has been
the first scientist to assess purification performance of planted filters in
Benin using phragmites (Deguenon, 2013). Now, three other species of plant will
be tested and their purification performances will be compared. So that a
technical document will be written and given to each municipal authority to
popularize reed bed process in every household in Benin.
The purification of
waste water in reed beds occurs in different stages. These stages are known and
have been developed by many scientists (Salt et al., 1998; Williams, 2002;
Vymazal, 2005; Imfeld et al., 2009; Reiche et al., 2010). According to
Calheiros et al. (2009), purification’s mechanism of waste water in reed beds
leans on physical, chemical and biological processes (Microbiological
degradation in the rhizosphere, absorption and plant metabolism). The
wastewater treatment process by planted filters is based on the principle of
fixed cultures that is to say of aerobic biological treatment in gravel layers
fine to coarse (Poulet et al., 2004). The gravel is not regularly renewed or
washed. In planted filter, wastewater are treated by firstly a filtration and
then anaerobic biological degradation (Seidel, 1967; Prigent, 2012). There are
two kinds of planted filtert ypes according to the flow direction: vertical
flow’s planted filters and horizontal flow’s planted filters. Only vertical
flow’s planted filters are experimented in this study. Several plants have been
used by scientists in reed beds. All Beninese plants have been listed in a book
named « flore analytique du Bénin ». To popularize reed beds in Benin, plants
have to be available and accessible to people. According to the combination of
information provided by the book named « flore analytique du Bénin » and the
list of plants often used in reed beds, three plants can be used in Benin for
reed beds: Typha domingensis, Panicum maximum and Echinochloa pyramidalis
Ouattara experimented one Panicum maximum planted filter basin to treat
domestic waste water. These domestic wastewater have the following
characteristics: 1519 ± 247 mg/l; 1256 ± 571 mgO2/l; 128 ± 58 mg/l et 6, 2 ± 2,2
mg/l respectively for TSS, COD, NH4 +, PO4 3- . With these domestic wastewater
Ouattara obtained the following purification yields: 91,4%, 85, 5%, 86, 5%, 74%
respectively for TSS, COD, NH4 +, PO4 3- (Ouattara et al., 2008). Korboulewsky
tested one Typha latifolia planted filter basin to treat domestic waste water.
These domestic waste water have the following characteristics : 7360 mg/L, 6055
mg/L,211 mg/L, 37mg/L respectively for TSS, COD, TKN, TP. With these domestic
waste water Korboulewsky obtained the following purification yields: 99,9%;
98,5%; 99,5% et 99,2% respectively for TSS, COD, TKN, TP. Ouattara and
Korboulewsky used vertical flow for their planted filter. Korboulewsky’s
domestic waste water are higher concentrated than Ouattara’s domestic waste
water. Nevertheless, when Ouattara’s purification yields are compared to
Korboulewsky’s yields, Typha latifolia’s yields seems to be upper than Panicum
maximum’s yields. So despite the fact that Korboulewsky used higher
concentrated waste water, Typha latifolia’s purification yields is upper than
Panicum maximum’s purification yields. In other words, Typha latifolia’s
purification capacity is exceptional. Kengne experimented one Echinochloa
pyramidalis planted filter basin to treat faecal sludge. Kengne obtained the
following purfication yields : 92%, 98% and 78% respectively for COD, TSS and
NH4 + (Kengne, 2008). If a purification capacity classification from higher to
lower is made for these three plants (Typha latifolia, Panicum maximum and
Echinochloa pyramidalis), Echinochloa pyramidalis will be the first in this
diagram, then Typha latifolia and Panicum maximum will be the last one. The aim
of this study is to compare the purification capacity of three plants (Typha
domingensis, Panicum maximum and Echinochloa pyramidalis) in order to show if
Echinochloa pyramidalisis is also the highest purification plant in Beninese
weather conditions.
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