Optimization of an integrated sponge--granular activated carbon fluidized bed bioreactor as pretreatment to microfiltration in wastewater reuse

Performance of submerged membrane bioreactor (SMBR) with and without the addition of the different particle sizes of GAC as suspended medium

In this study the effect of different particle sizes of granular activated carbon (GAC) on the performance of a submerged membrane bioreactor (SMBR) was investigated. The sizes of GAC used were 150-300, 300-600 and 600-1200 μm. The SMBR was operated at a filtration flux of 20 L/m(2)h. The removal of dissolved organic carbon (DOC) and chemical oxygen demand (COD) with the addition of GAC was 95%. The concentration of biopolymers, humic, building block and low molecular weight neutral and acids in the SMBR effluent was reduced by 20%, 66-76%, 20-50%, 30-56%, respectively. It helped to reduce the sludge volume index (SVI) and transmembrane pressure (TMP) development by 30-40% and 58%, respectively. However, the removal of NH₄(+) and PO₄(3-) was relatively low of 35-45% and 34-43%, respectively. The SMBR effluent was rich in PO₄(3-) and was removed/recovered using hydrated ferric oxide (HFO). The removal of PO₄(3-) was almost 90%.

Optimization of struvite crystallization protocol for pretreating the swine wastewater and its impact on subsequent anaerobic biodegradation of pollutants

Higher contents of NH(4)(+) and SS in wastewater hamper the anaerobic digestion; necessitating its pretreatment to reduce them. This study reveals optimization of struvite/MAP precipitation protocol followed by anaerobic digestion of pretreated swine wastewater for pollutants removal. Levels of different treatments: stirring speeds, 400 and 160 rpm; pH values, 9.0, 9.5, 10.0, 10.5, 11.0 and 11.5; and P:Mg:N ratios, 1:1:1.2, 1:1:1.7, 1:1:2.2, 1:1:2.7, 1:1:4.0 and 1:1:5.0 were evaluated for MAP crystallization. Among various combinations, protocol comprising of initial 10 min stirring at 400 rpm followed by 160 rpm for 30 min, pH 10.0, and P:Mg:N ratio 1:1:1.2 rendered the best removal efficiency for NH(4)(+), PO(4)(3-), COD, TC and TOC. Subsequent anaerobic biodegradation revealed superiority of MAP supernatant over raw swine wastewater for methane yield and NH(4)(+)-N, PO(4)(3-)-P, COD, TC and TOC removals. It suggests that struvite precipitation as pretreatment to anaerobic digestion is highly effective and advantageous in wastewater treatment.