Abstract
A preliminary study was conducted for the removal of turbidity (TD), chemical oxygen demand (COD) and biochemical oxygen demand (BOD) from secondarily treated sewage (STS) water through the electrolytic batch mode experiments with DC power supply (12 V) up to 30 min and using a novel concept of electrode combinations of different metals. The different surface areas (40, 80, 120 and 160 cm2) of the electrodes as a function of cross-sectional area of the reactor and the effect of inter-electrode distances (2.5–10 cm) on the electrolysis of STS water were studied. This study revealed that the effluent can be effectively treated with the aluminum (Al) and iron (Fe) electrode combinations (Al–Fe and Fe–Al). The maximum removal of TD (81.51 %), COD (74.36 %) and BOD (70.86 %) was recorded with Al–Fe electrode system, while the removal of these parameters was found to be 71.11, 64.95 and 61.87 %, respectively, with Fe–Al electrode combination. The Al–Fe electrode combination had lower electrical energy consumption (2.29 kWh/m3) as compared to Fe–Al electrode combination (2.50 kWh/m3). The economic evaluation of electrodes showed that Al–Fe electrode combination was better than Fe–Al electrode combination. This revealed the superiority of aluminum as a sacrificial electrode over that of iron which can probably be attributed to better flocculation capabilities of aluminum than that of iron.
Highlights
Water is an essential substance for living system as it allows the transport of nutrients as well as waste products in the living systems
Removal of chemical and biological impurities from the contaminated water system by the process of electrolysis is governed by several factors including electrode material and distance between them, time of electrolysis, electrical parameters such as voltage and current densities, pH of the system and last but not the least the presence of other coagulants in the system, This preliminary study was devoted to figure out effects of electrode systems consisting of different materials on secondarily treated sewage (STS) water treatment
The removal percentage of TD, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) increased progressively with decrease in inter-electrode distance from 10.0 to 2.5 cm, whereby it exhibited the maximum removal of TD (65.9 %), COD (57.41 %) and BOD (59.56 %) at the shortest distance (2.5 cm) between the electrodes (Al and Fe) with each electrode area of 80 cm2, whereas the Fe and Al electrode combination showed the removal of TD (59.66 %), COD (56.46 %) and BOD (51.99 %) (Figs. 2, 3)
Summary
Water is an essential substance for living system as it allows the transport of nutrients as well as waste products in the living systems. The use of sacrificial electrodes of metals which can give rise to multiple charged ions and their corresponding salts in the electrolytic systems results in coagulation and flocculation of dissolved and undissolved water impurities. This helps in the removal of contaminants from wastewater. Carmona et al (2006) reported that Al or Fe was usually used as electrode material and their actions were generated by the dissolution of sacrificial anodes upon the application of a direct current This electrolytic process of generating metallic hydroxide flocks in situ via electro-dissolution of the sacrificial anode immersed in the waste water is referred to as electrocoagulation (EC). The generation rate of flocks can be controlled by applying varying amount of current
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