Treatment of wastewater containing formaldehyde in a novel rotating biological contactor

A novel rotating biological contactor (RBC) was designed to remove formaldehyde in wastewater from industrial discharges. This model consisted of 2 chambers filled with random pickings of KMT (kaldness miliotechnique) type with the specific surface area of 500 m2/m3. The reactor was fed continuously with molasses, nutrient and formaldehyde solution of 37% .formaldehyde concentration increased gradually from 10 to 1000 ppm at different hydraulic retention times (HRT) of 8 ,12 ,24 ,48 hr while the total COD was fixed at 1000 mg/l. To study the inhibitory effect of formaldehyde on the wastewater treatment efficiency the ratio of formaldehyde COD to total COD varied from 0.17 to 1. The maximum formaldehyde removal efficiency was obtained at the ratio of 0.34 (formaldehyde concentration of 200mg/l) at HRTs of 48, 24, 12 hr, while at HRT of 8hr the optimum ratio was 0.2 (formaldehyde concentration of 120mg/l). The first stage of RBC was the most efficient stage as approximately 92% of formaldehyde removed in this stage. The results indicated that the second stage of the RBC was especially important at lower formaldehyde loadings (67 to 1340 mg formaldehyde /m2.d) .The experimental results revealed that KMT packing type has significant effects in the performance of the novel RBC. This type of packing enhanced the specific surface area for the biomass growth and they retained 20.2 to 65 gr MLVSS/m2 which is considerably high in compare with the amounts of attached biomass in the conventional RBCs.

Keywords:

Rotating Biological Contactor (RBC) , Formaldehyde Wastewater , KMT , Formaldehyde Inhibitation