Removal of phosphorus and suspended solids in aquaculture wastewater by using ferrous sulphate in coagulation process via zeta potential and particle size measurements
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Date
2018-06
Authors
Mohammad Firdaus Rakbi
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Abstract
A study was conducted to analyse the level of water quality that is discharge from
a local Arowana aquaculture farming pond system located at Simpang Empat,
Semanggol, Perak along the PLUS Highway at Bukit Merah (5°01’00.3”N,
100°38’15.4”E). At the aquaculture farm, the selected water quality parameter which
were BOD, COD, TSS, P and E.coli of inflows and discharges were measured. Ferrous
sulphate hydrate (FeSO4.7H2O) was selected as a coagulant to treat the aquaculture
wastewater in the coagulation process in order to reduce the amount of pollution from
the aquaculture ponds. Pollution such as suspended solids and phosphorus had been
stated as one of the aquaculture industry issues by the Department of Fisheries, Malaysia
which can affect the growing population of aquatic species and cost consumption of
aquaculture sector. The main objective of this study was to apply the zeta potential and
particle size measurements in determining the optimum pH and coagulant range to treat
the aquaculture wastewater. The wastewater characteristics study result showed the
value of TSS and P for discharges are 107 mg/L and 0.36 mg/L, respectively. This was
subsequently followed by a pH study to determine the optimum pH by using the zeta
potential and corresponding particles size with pH 2 to pH 12 for both wastewater sample
and FeSO4.7H2O which were determined separately. From the result obtained, the
suitable pH values to be used in coagulation process are pH 5 and pH 9. Next, the
aggregation and disaggregation behaviour of the wastewater suspension was analysed as
a function of a coagulant concentration. From this method, the suitable concentration of
FeSO4.7H2O to be used in coagulation process was found to be 600 mg/L for pH 5 and
800 mg/L at pH 9. The last phase of the study was the jar test experiment which was
carried out by using pH 5 with 600 mg/L of FeSO4.7H2O concentration and pH 9 with
800 mg/L. From the result obtained, P for pH 5 and pH 9 were 0.05 mg/L and 0.005
mg/L with percentage removal of 86.1% and 98.6%, respectively. Meanwhile, the result
for TSS obtained was same for both pH 5 and pH 9 which is 2 mg/L with percentage
removal of 98.1%. Hence, the best removal for P and TSS in this study was at pH 9 with
800 mg/L concentration of FeSO4.7H2O.