OPTIMIZATION OF COAGULATION-FLOCCULATION PROCESS FOR THE TREATMENT OF WASTEWATER USING NATURAL COAGULANTS

Abstract

The coagulant activity of Abelmoschus esculentus (okra) mucilage, Bridelia ferruginea tree bark extract and Ficus exasperata (sand-paper fig-tree) bark extract as natural coagulants was investigated and their efficiency was compared to Aluminium sulphate (a chemical coagulant) to treat both industrial and domestic wastewater. The control wastewater sample was coagulated with Al2 (S04)3 alone. The varying in percentage of natural coagulant to inorganic coagulant was in mix proportion of 0 % to 100 % added to 250 ml of wastewater sample. Thereafter, the percentages of natural coagulants were increased continuously to 10 %, 20 %, 30 %, 40 %, 50 %, 60 %, 70 % 80 %, 90 % and 100 % while inorganic coagulant was decreased to 90 %, 80 %, 70 %, 60 %, 50 % 40 %, 30 %, 20 %, 10 % and 0 %. Optimization assays were conducted using standard jar test method. The effect of pH, coagulant dosage on the percentage removal of chemical oxygen demand (COD) and turbidity were analyzed. For industrial wastewater sample, the highest turbidity and COD removal obtained was 95.9 % and 93.4 % respectively between the raw sample and the sample treated when inorganic coagulants (IC) was 20 % and natural coagulant (NC) was 80 % for Abelmoschus esculentus (okra) mucilage while the highest turbidity and COD removal obtained for Bridelia ferrugineae bark extract was 98.1 % and 91.0 % respectively between the raw sample and the sample treated at a mix ratio of 60 % inorganic coagulants (IC) and 40 % natural coagulant (NC). The highest value of turbidity and COD removal for Ficus exasperata (sand-paper fig-tree) bark extract was 87.5 % and 99.4 % respectively when the mix ratio was 10 % inorganic coagulants (IC) and 90 % natural coagulant (NC). For domestic wastewater, , the highest turbidity and COD removal obtained was 93.3 % and 95.3 % respectively between the raw sample and the sample treated with coagulant when inorganic coagulants (IC) was 10 % and natural coagulant (NC) was also 90 % for Abelmoschus esculentus mucilage (okra) while the highest turbidity and COD removal obtained for Bridelia ferrugineae bark extract was 98.6 % and 98.7 % respectively between the raw sample and the sample treated at a mix ratio of 10 % inorganic coagulants (IC) and 90 % natural coagulant (NC). The highest value of turbidity and COD removal for Ficus exasperata (sand-paper fig-tree) bark extract was 93.0 % and 99.2 % respectively when the mix ratio was 10 % inorganic coagulants (IC) and 90 % natural coagulant (NC). The three experimented natural coagulants used in optimizing coagulation-flocculation process showed high turbidity and COD removal for industrial wastewater and domestic wastewater at varied percentages