2.1. Effluent and Plant Collection The inlet and outlet Textile effluents were collected from the ETP of Echotex Ltd. located at Chandra Polli Biddut, Kaliakoir, Gazipur, Bangladesh. The inlet effluent was collected from the equalization tank of the ETP.
2.2. Chemicals and Testing Instruments For Jar Test of coagulation experiments, AR grade coagulants have been used and those were ferrous sulfate (FeSO4), potash alum (K2SO4.Al2(SO4)3.24H2O), ferric chloride (FeCl3) and calcium oxide (CaO). Following pocket-sized meters were used to measure pH and TDS. Specifications of the TDS meter: Pocket-Sized TDS Meter, Range: 100 / 1000 ppm, Model: HI 96302, Manufacturing Company: Hanna Instruments, Country of Origin: Italy. Calibration process: The TDS meter has been calibrated by a standard solution (1382 mg/L) as per operation manual of the manufacturer. Specifications of the pH meter: Pocket Sized pH Meter, Model: HI 96107, Manufacturing Company: Hanna Instruments, Country of Origin: Italy. Calibration process: The pH meter has been calibrated by three buffer solutions (pH = 7, pH = 4 and pH = 10) as per suggested method in operation manual of manufacturer.
2.3. Experimental Procedure for Treatment of Effluents with Aquatic/non Aquatic Plants At first the color, odor, TDS and pH values of the collected inlet and outlet effluents were measured. 50 mg of each plant was chopped into small pieces and easily immersed into the conical flask or beaker separately. The inlet[Figure 3(a)] and outlet effluents[Figure 3(b)] were taken in three conical flasks and three beakers respectively. Each of the conical flask or beaker contained 300 mL effluent sample.
Each of the conical flask and beaker was specified by an individual sample number (S-1 - S-6), after that the chopped plants were immersed in different conical flasks (containing inlet effluents) and beakers (containing outlet effluents) and shaken gently to mix-up with the effluent well. The contents of various samples were as follows. S-1: 300 mL inlet effluent + 50 mg of Water Hyacinth (Eichornia crassipes). S-2: 300 mL inlet effluent + 50 mg of Plantain Plant (Banana) Bark (Musa sapientum)[Figure 4(a)]. S-3: 300 mL inlet effluent + 50 mg of Water Lilies (Nymphaea nouchali). S-4: 300 mL outlet effluent + 50 mg of Water Hyacinth (Eichornia crassipes)[Figure 4(b)]. S-5: 300 mL outlet effluent + 50 mg of Plantain Plant Bark (Banana Tree Bark) (Musa sapientum)[Figure 4(c)]. S-6: 300 mL outlet effluent + 50 mg of Water Lilies (Nymphaea nouchali).
These samples were kept in the laboratory for 48 hours at room temperature for adsorption of pollutants on plants. After 48 hours, the samples were observed very carefully to detect the change of color, odor, TDS and pH of the treated effluents.
2.4. Experimental Procedure with Different Types of Coagulants (Jar Test) For Jar test seven types of coagulants were prepared for treating the inlet effluent which was collected in different vessels and marked with different sample numbers (S-1(a), S-2(b), S-3(c), S-4(d), S-5(e), S-6(f) and S-7(g)). The contents of the samples are given below.
S-1(a): 300 mL inlet effluent + 30 g FeSO4 + 10 g CaO + 100 mL tap water. S-2(b): 300 mL inlet effluent + 30 g K2SO4, Al2(SO4)324H2O + 10 g CaO + 100 mL tap water. S-3(c): 300 mL inlet effluent + 30 g FeCl3 + 10 g CaO + 100mL tap water. S-4(d): 300 mL inlet effluent + (15 g FeSO4 + 15 g K2SO4.Al2(SO4)324H2O) + 10 g CaO + 100 mL tap water. S-5(e): 300 mL inlet effluent + (15 g FeSO4 + 15 g FeCl3) + 10 g CaO + 100 mL tap water. S-6(f): 300 mL inlet effluent + (15 g FeCl3 + 15 g K2SO4.Al2(SO4)3 24H2O) + 10 g CaO + 100 mL tap water. S-7(g): 300 mL inlet effluent + (10 g FeSO4 +10 g K2SO4.Al2(SO4)3 24H2O+10 g FeCl3) + 10 g CaO + 100 mL tap water. The initial observations were recorded just after addition of various coagulants and final observations were recorded after two hours of coagulant addition.