Semiconductor wastewater treatment

Wuhan Tianma Electronic Co., Ltd 1) TianMa is LCD manufacturer, Wastewater source from cleaning and etching process, most of contamination are HF , CeO2, COD, NH3, acid, Flow rate: 190 m3/ h

• Flow diagram: Influent > EQ > 1st Anoxic > 1st Aeration > 2nd Anoxic > 2nd Aeration

  > flocculants tank > Sediment tank > Effluent 

• Tank size: Anoxic tank 1,000 m3 each, Aeration tank 2,000 m3 each 

• Project problem: NH4-N problem, Nitrification process doesn’t work

• Wastewater parameter: COD 88.6 mg/L, Nh4-N 72.5 mg/L, TN 97.6 mg/L

1) HF (Hydrofluoric Acid) is toxic and inhibit to micro-organism growth, need to increase resistance to toxic load; 

2) Biofilm formation not good, The good development of a biofilm may allow for an aggregate cell colony (or colonies) to be increasingly resistant to toxic load. 

3) Phosphate source is insufficient, biological ammonia reduction need to keep C:N:P at 100 :5 :1, need increase Phosphate to 3~4 mg/L 

4) Need to dilute wastewater to decrease inhibitions and biomass quick cultivation

1) Stop aeration and inflow in aeration tank.

2) Decant 2400 m3 wastewater from aeration tank. 

3) Add 1000 m3 tap water for dilution. 

4) Add 3% dry sludge to aeration tank for quick start up.

5) Inoculate 400 Liter nitrifying bacteria.

6) Add sodium phosphate for phosphate source.

7) Keep aeration for 24 hrs, once ammonia is significant controlled, then start to flow in

8) Subsequent dose 20 liter for 15 days to continue cultivate biomass. 

9) Daily check parameter until biomass cultivated.

After dosing the bacteria, the activated sludge is in good shape, The water in the clarify tank is obviously clear than before.