Abstract:
The objective of this study was to evaluate the performance of waste Peanuthull as a
biosorbent in treating ricemill wastewater. The performance of the peanuthull was
compared under similar conditions with coal based Granular Activated Carbon (GAC)
which is a well-known adsorbent for organic pollutants. The adsorbents were carefully
washed, dried, grinded and sieved to obtain uniform paricle size <1 mm. Batch adsorption
studies were conducted for peanuthull and GAC for varying doses (0 - 6 g/L) and contact
times (0 - 300 min) to determine the optimum dosage of adsorbents and contact time with
wastewater respectively at pH 8.0±0.25 and at temperature 28±20C. The performance
efficiencies of the adsorbents were tested based on the removal (%) of Nitrates,
Phosphates, five days-Biological Oxygen Demand (BOD5) and Chemical Oxygen Demand
(COD) from wastewater which was collected from a ricemill located in Vavuniya. Three
replicates were carried out for each test. The optimum removal of organics and nutrients
were observed with Peanuthull at the dose of 4 g/L, in which the removal efficiency of
BOD5, COD, nitrate and phosphate were 65, 70, 67 and 24% respectively. In comparison
with GAC, the optimum removals were noticed at the dose of 1 g/L in which the removal
efficiency of BOD5, COD, nitrate and phosphate were 90, 75, 56 and 24% respectively.
According to contact time of adsorbent with wastewater, the peanuthull attained optimum
removal at 120 mins whilst the GAC attained the optimum removal at 45 mins in which the
optimum doses of peanuthull and GAC were maintained at 4 g/L and 1 g/L respectively.
Based on t-test, the performance of peanuthull was similar to GAC in terms of COD,
nitrate and phosphate (p-value > 0.05) reduction from ricemill wastewater. Since the
adsorbent was prepared from waste Peanuthull and no chemicals are required, this can be
used as a cost-effective option and environmentally friendly biosorbent to treat ricemill
wastewater.
