Treatment of Bisphenol A-Containing Effluents from Aerobic Granular Sludge Reactors with the Use of Microfiltration and Ultrafiltration Ceramic Membranes.

This study investigated the use of ceramic membranes to remove total suspended solids (TSS), organics (expressed by chemical oxygen demand, COD), and bisphenol A (BPA) via microfiltration (MF, pore size 0.45 µm) and ultrafiltration (UF, cutoff 150 kDa) in post-treatment of effluents from aerobic granular sludge reactors (GSBRs). The efficiency of removal of COD, BPA, and TSS in MF was similar to that in UF; however, it was achieved at a lower pressure, which reduces energy consumption during the filtration process. Despite the similar quality of the permeates in MF and UF, the permeate flux averaged almost 20% higher in UF than in MF. The rejection coefficients were 77-82% for COD and 48-100% for BPA. In both MF and UF, TSS were totally removed. In the integrated system of aerobic granular sludge reactor and membrane installation, total removal of COD was 92-95% and that of BPA was above 98%, independently of the membrane technique. The high efficiency of BPA removal in MF and UF, despite pore sizes in the MF and UF membranes larger than the BPA molecules, suggests that some part of the BPA was first bound by particulate organic matter in the biologically treated wastewater before this sorbed form was removed by the membranes. Furthermore, the high removal of COD and BPA, even in MF, was attributed to adsorption on the membranes, in addition to sieve retention.

Nitrifying granules cultivation in a sequencing batch reactor at a low organics-to-total nitrogen ratio in wastewater.

It is possible to cultivate aerobic granular sludge at a low organic loading rate and organics-to-total nitrogen (COD/N) ratio in wastewater in the reactor with typical geometry (height/diameter = 2.1, superficial air velocity = 6 mm/s). The noted nitrification efficiency was very high (99%). At the highest applied ammonia load (0.3 ± 0.002 mg NH (4) (+) -N g total suspended solids (TSS)(-1) day(-1), COD/N = 1), the dominating oxidized form of nitrogen was nitrite. Despite a constant aeration in the reactor, denitrification occurred in the structure of granules. Applied molecular techniques allowed the changes in the ammonia-oxidizing bacteria (AOB) community in granular sludge to be tracked. The major factor influencing AOB number and species composition was ammonia load. At the ammonia load of 0.3 ± 0.002 mg NH (4) (+) -N g TSS(-1) day(-1), a highly diverse AOB community covering bacteria belonging to both the Nitrosospira and Nitrosomonas genera accounted for ca. 40% of the total bacteria in the biomass.

The effect of different nitrogen sources on denitrification with PHB under aerobic condition.

This study investigated the effectiveness of denitrification under aerobic conditions depending on nitrogen forms in synthetic wastewater (ammonium, or ammonium and nitrite). Activated sludge was cultivated in a sequencing batch reactor with municipal wastewater enriched by acetate. Poly-beta-hydroxybutyrate (PHB) was accumulated in activated sludge to 0.35 g PHB g(-1) VSS. Activated sludge, cultivated in such conditions, was used in further experimental series. The duration of each series was 24 h. Two types of synthetic wastewater, with acetate as the carbon source, were used in this study. One type of wastewater contained only ammonium; the second one was enriched also by nitrite. The amount of nitrogen reduced by the microorganisms in the activated sludge was 22.5 mg N(red) l(-1) when ammonium was the only nitrogen source in wastewater, and a 3-fold increase was observed in the presence of two nitrogen sources: ammonium and nitrite. Simultaneous consumption of organic substances in wastewater (external source of electron donors) and intracellularly stored poly-beta-hydroxybutyrate in activated sludge (endogenous carbon source) was revealed. COD consumption to reduce 1 mg N-oxides, in series with wastewater containing ammonium, was 8.4 mg COD. However, in series using wastewater with ammonium and nitrite, a 3-fold decrease in COD/N(red) ratio was observed.

Effect of volumetric organic loading on the nitrogen removal rate by immobilised activated sludge.

Activated sludge was immobilised in a porous ceramic carrier to create a stationary core of a bio-reactor. Municipal wastewater was treated in this reactor under varied conditions of volumetric organic loading rate (expressed by chemical oxygen demand (COD)) that were the following: 6.5, 8.0, 20.8, 48.8 g COD l(-1) d(-1). The rate constants of ammonification, nitrification and denitrification under aerobic conditions were determined. All rate constants increased with a growth in volumetric loading rate, but the highest loading value of 48.8 g COD l(-1) d(-1) limited the ammonification and nitrification rates.