Phosphorus Co-Precipitation in the Biological Treatment of Slaughterhouse Wastewater in a Sequencing Batch Reactor

The effect of phosphorus co-precipitation with ferric chloride $\left({\mathrm{FeCl}}_3\right)$ dosing on biological phosphorus (P) along with carbon (C) and nitrogen (N) removal was investigated in a sequencing batch reactor (SBR) for slaughterhouse wastewater treatment. Additional phosphorus removal due to chemical co-precipitation was evaluated as the difference in System P removal between Phase 1 (control—without ${\mathrm{FeCl}}_3$ dosing) and Phase 3 (with ${\mathrm{FeCl}}_3$ dosing). Phase 2 was mainly studied to improve nitrification/denitrification process with acetate addition by Filali-Meknassi et al. in 2004. Both systems (Phases 1 and 3) exhibited high P removal but a co-precipitation with ${\mathrm{FeCl}}_3$ dosing only allowed us to have an orthophosphates $\left(o\text{-}{\mathrm{PO}}_4\right)$ concentration below $1\mathrm{mg}\mathrm{P}∕\mathrm{L}$ in the effluent. Without ${\mathrm{FeCl}}_3$ addition, the total P concentration was reduced from $85\pm 12$ to $14\pm 2\mathrm{mg}\mathrm{P}∕\mathrm{L}$ (84% removal), whereas with the addition of ${\mathrm{FeCl}}_3$ an additional $11\mathrm{mg}\mathrm{P}∕\mathrm{L}$ was removed bringing the effluent P concentration to $3\mathrm{mg}\mathrm{P}∕\mathrm{L}$ (as total P). Although, during simulation of aerobic phase, a release of phosphorus was observed. The study showed that the ASM2d model with the adjustment (calibration) of seven kinetic parameters ( ${\eta }_{{\mathrm{NO}}_3}$ , ${\mu }_{\mathrm{AUT}}$ , $b_{\mathrm{AUT}}$ , $K_{{\mathrm{O}}_2}$ , $K_{{\mathrm{NH}}_4}$ , $K_h$ , ${\mu }_{\mathrm{PAO}}$ , and ${\mathrm{b}}_{\mathrm{PAO}}$ ) was capable of predicting the behavior of the laboratory SBR activated sludge and provided the profile of nutrients (phosphorus, ${\mathrm{NH}}_4–\mathrm{N}$ , ${\mathrm{NO}}_X–\mathrm{N}$ , and COD) removal.