The deep BAF process for PCB waste water (3)

3.2 BAF impact on the rest of the water quality indicators

3.2.1 wastewater pH changes

raw water after the factory original coagulation precipitation process preliminary treatment, when entering the BAF system average pH 9.0, basic on the verge of overweight and direct emissions may be the cause of river pollution, soil alkalization, etc. Using BAF process, due to the microbial nitrification system consumes basicity (mainly NH4 +) in waste water, the water pH basic remain at around 7.9, standard ensures water at any time.

3.2.2 the change of ammonia nitrogen in wastewater

Wastewater after treated with BAF system declined, of ammonia nitrogen in water by 19.86 mg/L fell to 13.89 mg/L, but has yet to reach discharge standards, this is due to the best of nitrifying bacteria, proliferation and survival temperature is 25 ℃, while during the experiment system in a row after the water temperature maintained in 11 ~ 16 ℃, under the temperature of BAF in the growth and activity of nitrifying bacteria is restrained, resulting in poor ammonia nitrogen removal efficiency.

3.2.3 waste water in copper complexing state changes

The copper ammonia wastewater mainly complex ion (Cu (NH3) 2 + 4) exist, Cu2 + is very little.BAF role to eliminate the Cu complex in from [Cu (NH3) 2 + 4) isolated Cu2 +, OH - from their response to that of the wastewater generated Cu (OH) 2 precipitate, which was BAF biological flocculation adsorption.

BAF process in the wastewater Cu complexing state overall declining (1.40 mg/L to 0.82 mg/L), but the water was not up to standard. This is because the BAF nitrification and the Cu (OH) 2 is the best temperature flocculation adsorption 20 ~ 30 ℃, and the system straight into the water after the water temperature maintained at 11 ~ 16 ℃, seriously inhibit the adsorption of biofilm activity, lead to the removal of Cu effect is not very ideal.

4. Conclusion

(1) using the depth of the BAF process a printed circuit board factory PCB wastewater treatment, when the water COD load of 0.12 kg/(m3 · d), average inlet COD is 187.8 mg/L, the process average effluent COD can be dropped to 41.8 mg/L; When water COD load up to 0.36 kg/(m3 · d), the average COD water can also fell to 42.1 mg/L, fully meet the local relatively strict wastewater discharge standard requirements.

(2) Because the backwash water quality to suit the requirements of discharge standards, emissions should be to adjust the pool to processing. Backwash cycle is about 15 d.



(3) During the experiment temperature is 11 ~ 16 ℃, BAF in the growth and activity of nitrifying bacteria is restrained, flocculation adsorption activity of the biofilm, ammonia nitrogen and complexing state Cu removal effect is not very ideal. Need to consider to take corresponding measures to improve the filter water temperature or appropriate to ammonia nitrogen in water and Cu for further processing.