Removal of turbidity from washing machine discharge using Strychnos potatorum seeds: Parameter optimization and mechanism prediction

Investigation on the removal of contaminants from washing machine discharge using Strychnos potatorum (clearing nut) - A potential purifying agent

The objective of the present study is to develop eco-friendly purifying agents from natural materials, Strychnos potatorum (SP) - a coagulant. The seeds of SP were used for wastewater treatment (washing machine effluent). Physico-chemical parameters like turbidity, total dissolved solids (TDS), electrical conductivity (EC), pH, calcium (Ca2+), magnesium (Mg2+) and phosphate (PO43-) were tested and the data obtained were compared with BIS standards. In the current work, physical and chemical parameters have been examined to determine the quality of water for washing machine discharge, before and after treatment (coagulation) using SP seeds. The testing procedure was carried out using a Jar test of coagulant mass 1000 mg/L with rapid mixing at 150 rpm for 5 min, slow mixing at 30 rpm for 25 min and a settling period of 1 h. Coagulation results were reported for the use of SP seeds, where the effectiveness of removing turbidity and PO43- was determined to be 81.54 and 41.45%. The presence of various functional groups in SP seed was assessed by fourier transform infrared (FT-IR) spectroscopy. Qualitative identification of phytochemical constituents of seed extract for this species was also carried out. The experimental findings strongly highlighted the ability of SP seeds to remove turbidity and PO43- from wastewater.

Modeling and optimization of the coagulation/flocculation process in turbidity removal from water using poly aluminum chloride and rice starch as a natural coagulant aid

The application of the coagulation/flocculation process is very important due to its simplicity in removing turbidity. Due to the disadvantages of using chemical coagulants in water and the lack of sufficient effect of natural materials alone in removing turbidity for proper performance, the simultaneous use of chemical and natural coagulants is the best way to reduce the harmful effects of chemical coagulants in water. In this study, the application of poly aluminum chloride (PAC) as a chemical coagulant and rice starch as a natural coagulant aid to remove turbidity from aqueous solutions was investigated. Effects of the above coagulants on the four main factors, coagulant dose (0-10 mg/L), coagulant adjuvant dose (0-0.1 mg/L), pH (5-9), turbidity (NTU 0-50), and each five levels were assessed using a central composite design (CCD). Under the optimized conditions, the maximum turbidity elimination efficiency was found to be 96.6%. The validity and adequacy of the proposed model (quadratic model) were confirmed by the corresponding statistics (i.e., F-value of 23.3, p-values of 0.0001, and lack of fit of 0.877 for the model, respectively, R2 = 0.88, R2adj. = 0.84, R2 pred = 0.79, AP = 22.04).

Equilibrium Isotherms, Kinetics, and Thermodynamic Mechanisms of a Novel Polyacrylamide-Strychnos potatorum Seed-Derived Activated Carbon Composite for Aqueous Hardness Removal

Hardness in water is responsible for both residential and industrial problems. Moreover, drinking hard water is suspected as the main cause of chronic kidney disease of unknown etiology (CKDu) in Sri Lanka. The major constituents that are responsible for water hardness are calcium and magnesium ions. In this study, a composite was synthesized using activated carbon of Strychnos potatorum seeds (ACSP) and acrylamide to remove hardness in drinking water. The synthesized composite was characterized using Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectroscopy and scanning electron microscope (SEM). According to this study, the process of removal of hardness depends on the contact time, adsorbent dosage, initial contents, and pH of the solution. The adsorption data were well fitted to the Freundlich isotherm and the pseudo-second-order kinetic models. Furthermore, environmental samples collected from Anuradhapura, Sri Lanka, which is well known for water with high hardness, were treated with an adsorbent, and hardness was reduced effectively. Moreover, the adsorption appeared to be spontaneous in nature. Finally, it can be concluded that this adsorbent can be used as an effective hardness-removing agent.