Physical Treatment Of Drinking Water Using Natural Coagulants (Rice Husk, Rice Husk Ash And Peanut Shell)

Abstract

In developing countries lack of adequate and potable water is the main problem. When surface water is used for drinking water production, turbidity removal is an essential part. It is generally achieved by coagulation process. Therefore, this study was conducted to investigate the efficiency of rice husk, rice husk ash and peanut shell as natural coagulant with the objectives of characterizing physical characteristics of the water sample, evaluate turbidity, color and total solid removal efficiency of the coagulants and determine optimum dose and optimum settling time of the coagulants. The study involved preparing natural coagulants, collecting sample from Jimma town treatment plant, characterization of sample before and after treatment, treatment of sample using natural coagulants and finally analysis of data by using Design Expert version 11. The study was conducted at Jimma Institute of Technology Environmental Engineering laboratory during 2018/19. Generally 36 jar test runs were conducted 18 for peanut shell, 9 for rice husk and 9 for rice husk ash. Analysis of variance revealed that there was significance difference among the coagulant dose, particle size and settling time. The natural coagulant made from rice husk recorded the best removal of 87.42% turbidity, 88.97% color, and 71.01% total solids. The rice husk ash reduced turbidity, color and TS by 95.09%, 96.09% and 97.46% respectively. This efficiency achieved on 1.5 gram dosage of rice husk and rice husk ash at 45 minutes settling time and with optimum pH of 6.5. The effect on pH was ranging between 16.24 and 18.12%. This indicated that applied rice husk and rice husk ash in coagulation process is an effective means for removing turbidity, color and total solids present in raw water. The result from peanut shell reported that 76.22% removal of turbidity, 59.03% removal of color and 60.61% removal of TS. These highest values were recorded at minimum dose of 0.5 gram and 45 minutes settling time by coagulant size of 0.3mm with relatively neutral pH of 6.5. The result showed that 56.76 %, 58.49% and 57.4% turbidity color and TS removal efficiency respectively was obtained by 0.425mm coagulant size, at 0.5 gram dose. For both coagulants size, the pH was best adjusted by using 1.5 gram of extracted coagulant. Further increases in coagulant dose of peanut shell beyond the optimal value had negative effect on turbidity removal. Coagulant activity of peanut shell, rice husk and rice husk ash were about (76.22%, 87.42% and 95.09% respectively) found to be equal to other natural organic coagulants. The performance of rice husk, rice husk ash and peanut shell for turbidity, color and total solid removal from source water is very appreciable and environmental friendly. It is better to study the removal efficiency of peanut shell on raw water by using filter paper. This finding, being the result of limited particle sizes, it is recommended that the experiment should be repeated with more particle sizes, stirring speed and chemical and biological characteristics to confirm obtained results.