Electro-coagulation treatment efficiency of graphite, iron and aluminum electrodes using alum and wood ash electrolytes on a Kraft pulp and paper mill effluent

摘要

Specific power consumption and reduction of BOD, COD, TS, pH, and chemical elements werenused to determine the treatment efficiency of Fe, graphite and Al electrodes with alum and woodnash as supporting electrolytes on the effluent from a Kraft pulp and paper mill in Kenya. Fivensampling points were selected along mill’s effluent treatment system: primary settling tank (SP1),nfirst aerated lagoon (SP2), second aerated lagoon (SP3), stabilization pond (SP4), and at dischargenpoint (SP5). Operating costs were also compared between treatments. Graphite electrodesncombined with alum showed the lowest power consumption (0.5 to 3.9mWh/m3), followed bynAl and Fe. All the electrodes reduced color from a maximum of 3,2008H to the minimum localnstandard of 158H. However Al electrode with alum was the most effective method for BOD andnCOD reduction by over 60% and 58.8% respectively and generated less sludge at all samplingnpoints. The cost of treatment was lowest with graphite electrode (US$0.006 to 0.0008 per m3nof effluent), but highest with Al electrodes combined with wood ash (US$31.74 to 8.34 per m3).nFurther study is required for the effectiveness of increasing the concentration of wood ashnleachate at higher concentration and current density.