Waste Pickle Liquor Utilization as a Coagulant for Water Treatment Process

by Agy Yogha Pradana, Ahmad Faisal, Dzaky Abdul Hanif

Publisher - PT Krakatau Steel (Persero) Tbk. Indonesia

Category - Engineering & IT

Waste Pickle Liquor (WPL) is waste of pickling process in Continuous Pickling Line (CPL) at Cold Rolling Mill (CRM). CPL produce 35 m3 /shift WPL which contains 80-150 g/L ferrous ion and 4 – 7% HCl. WPL is processed in Acid Regeneration Plant (ARP) to regenerate HCl and also produce Fe2O3 as by product. Currently, ARP only processed 20 – 25 m3 /shift WPL and around 10-15 m3 /shift excess WPL need to be taken by third parties, since it cannot disposed directly to the environment. Fortunately, ferrous ion in WPL can be oxidized into ferric ion and used as coagulant in water treatment process. This study aim to produce coagulant from WPL by using two methods: (1) WPL oxidation by H2O2 and (2) WPL oxidation by HOCl generated from electrolysis. Based on the jar test result using raw water with specification pH 7 – 8; DHL 200 – 250 µS/cm; Turbidity = 40 - 75 NTU; Color = 300 – 700 Pt.Co, coagulant produced by first method can purify the water into pH 5.5 – 4; DHL 240 - 300 µS/cm; Turbidity = 1 - 2 NTU; Color = 20 – 30 Pt.Co, meanwhile coagulant produced by second method can purify the water into pH 3 – 3.5; DHL 500 - 600 µS/cm; Turbidity = 1 - 2 NTU; Color = 10 – 20 Pt.Co. The result from coagulant produced by first and second method has already meet the target of desirable water specification which Turbidity ≤ 3 NTU, Color ≤ 30 Pt.Co, but the water production cost, compared with water production cost in one of water treatment company in Cilegon, first coagulant is 143% and second coagulant is 63.8%. Due to excess HCl in WPL, indicated by low pH in purified water, sufficient amount of iron scrap can be added into WPL before oxidation, so the ferric content will increase after oxidation and decrease coagulant consumption / m3 raw water, which reduce coagulant conversion cost. With this result, this study not only able to solve waste handling problem at Krakatau Steel but also create additional value to WPL and effectively help to increase innovation sense of Krakatau Steel Personnel.

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