The iron-carbon micro-electrolysis method was applied to pretreat the cleaning wastewater produced during boiler tube acid washing

the organic acid consists formic acid and glycolic acid with high COD.The effects of the ratio of cast-iron scrap to activated carbon

the pH value of the wastewater

the packing loading ratio(namely the ratio of packing quality to wastewater quality)

the reaction temperature and the residence time on the COD removal ratio of wastewater were investigated.The results show that

the highest COD removal rate(33.9%)was obtained under the optimal conditions:the ratio of cast-iron scrap to activated carbon of 1∶2

the initial pH value of the wastewater of 2.85

the packing loading ratio of25%

the reaction temperature of 30 ℃ and the residence time of 3h.After 5times reaction

the COD removal rate was still as high as 32.1%.The increase of the wastewater's pH value may be the major reason for the inhibition of the organics continuous degradation.