06-11-2012, 01:32 PM
MORINGA OLEIFERA SEEDS FOR SOFTENING HARDWATER
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Abstract
In this paper, preliminary investigations into the possible use of Moringa
oleifera seed suspension for the softening of hardwater are presented. Four water
sources: synthetic water (distilled water spiked with calcium chloride), naturally hard
surface water and groundwater from two tube wells at different locations were used for
the study. Modified laboratory jar test procedures for coagulation studies were used for
the experimental runs. Water hardness from the sources varied from 300 up to 1000 mg/l
as CaCO3 . The mechanism for softening was found to be due to adsorption with the
adsorption isotherm approximating to the Langmuir type, and conversion of soluble
hardness-causing ions to insoluble products by precipitation reactions. Removal
efficiency was found to increase with increasing dosage of Moringa oleifera. Higher
dosages were required to achieve equivalent residual hardness for water samples with the
same initial hardness but higher number of hardness-causing species in the water.
Hardness removal was found to be independent of pH of the raw water.
INTRODUCTION
Moringa oleifera belongs to the family Moringaceae which is a single genus family
of shrubs and trees cultivated across the whole of the tropical belt and used for a variety
of purposes (Jahn, 1986). The dry seed suspension is known to be a natural coagulant
and coagulant aid (Jahn, 1979-1988; Folkard et al., 1986-1988; Kaser et al., 1990; Sani,
1990; Bina, 1991).
In the Sudan, dry Moringa oleifera seeds are used in place of alum by rural women to
treat highly turbid Nile water (Jahn, 1986). In Northern Nigeria, the fresh leaves are used
as a vegetable, roots for medicinal purposes and branches for demarcation of property
boundaries and fencing. Studies by Eilert et al. (1981) identified the presence of an
active antimicrobial agent in Moringa oleifera seeds. The active agent isolated was found
to be 4a L-rhamnosyloxy-benzyl isothiocyanate, at present the only known glycosidic
mustard oil. Madsen et al. (1987) carried out coagulation and bacterial reduction studies
on turbid Nile water in the Sudan using Moringa oleifera seeds and observed turbidity
reduction of 80-99.5% paralleled by a bacterial reduction of 1-4 log units (90-99.9%)
within the first one to two hours of treatment, the bacteria being concentrated in the
coagulated sediment.
Preparation of Moringa oleifera seed suspension
Dry Moringa oleifera seeds were from Langen Local Government area of Kano
State, Nigeria. The seed wings and coat from selected good quality Moringa oleifera
seeds were removed and the kernel ground to a fine powder using the coffee mill
attachment of a Moulinex domestic food blender.
Two grams of the powder were put in a high speed mixer (ATO MIX MSE) and 200
ml distilled water added and blended for 30 s to extract the active ingredient. The
resulting suspension was filtered through a muslin cloth and the filtrate made up to 500
ml to give a stock solution of approx. 4000 mg/l. The solution had a pH of 6.5. The
stock solution was prepared fresh for use as and when needed, since deterioration sets in
if stored for more than two days at room temperature.
Experimental runs
For each experimental run 500 ml of water sample was put in a one litre beaker and
the paddle of a jar apparatus (Voss Flocculator) inserted. The speed of mixing was set at
110 rpm using a portable electronic tachometer (Banair). The required dosage of
Moringa oleifera was added and stirred for 2 min. The residual hardness of the product
water was then measured using standard methods (APHA, 1992) after one hour settling
time. The synthetic water sample was kept at constant pH of 7.2 for all experimental
runs. For the surface and groundwater samples, water quality parameters measured
before and after dosing were hardness, alkalinity, turbidity and pH.