A case study of wastewater treatment and reuse in a circuit board enterprise

Abstract

The production wastewater of a circuit board enterprise comes from the printing plate washing wastewater,developing and post-developing cleaning wastewater, deinking cleaning wastewater, etching cleaning wastewater, pre-treatment cleaning wastewater, intermediate treatment cleaning wastewater, and OSP antioxidant cleaning wastewater. The produced wastewater in this project was divided into high-concentration organic wastewater, etching cleaning wastewater, and general cleaning wastewater for separate pretreatment, and then converged for biochemical treatment and advanced treatment. The results showed that the COD, BOD5, NH3-N, and SS of the discharged wastewater after treatment were ≤95 mg/L, ≤22.4 mg/L, ≤11.3 mg/L, and ≤78 mg/L, respectively, which reached the indirect emission limit of the “Electronic Process Water Pollutant Emission Standards”(GB 39731—2020) and the second-stage secondary emission standard of the “Water Pollutant Emission Limits”(DB 44/26—2001) in Guangdong Province. The COD, BOD5, NH3-N, and conductivity of the reclaimed water were ≤27 mg/L, ≤8.14 mg/L, ≤2.4 mg/L, and ≤843 μS/cm. After meeting the process and product water standards of “Recycling of Urban Sewage for Industrial Water Quality”(GB/T 19923—2005), it could be reused for etching, deinking, and other production processes. The direct operating cost of wastewater treatment in this project was 10.54 yuan/ton of water, and the cost of reclaimed water treatment was 2.72 yuan per ton of water.

Keywords

• circuit board wastewater
• reclaimed water
• acid precipitation
• alkaline-stripping
• reverse osmosis