Mature granules and flocs from aerobic sludge were collected from the wastewater treatment plant (WWTP) treating both municipal and industrial effluents in Haining city China. This plant has been operating under conditions favoring aerobic granular sludge formation, for over 3 years, suggesting that the granules, which stably retained under changing effluent conditions, may contain unique microbial populations. Microbial analysis indicated that the granular sludge was primarily composed of Planctomycetes, Proteobacteria and Bacteroidetes from the bacterial phyla. Interestingly, microbial communities were also observed to be stratified between the structural features of the sludge. For example, Euryarchaeota was found to make up the majority of the archaea found in the granules while Methanosaeta was dominant in the flocs. Additionally, granules were found to contain, 34 phyla and 222 genera of bacteria, 4 phyla and 13 genera of fungi, and 2 phyla and 17 genera of archaea. While flocs contained, 32 phyla and 203 genera of bacteria, 6 phyla and 26 genera of fungi, and 2 phyla and 12 genera of archaea. This biodiversity signifying a preservation of bacterial and archaeal population in granules, and fungal populations in flocs may result from the sedimentary characteristics of the granules. This suggests microbes uniquely associated in the granules are playing a key role in structure formation and stability of the granular ecosystem, which is maintained by the longer sludge retention time.

•It is first time to cultivate aerobic granules in continuous-flow RFBR.•Several cells used, flow direction reversed, settling time controlled in RFBR.•Periodic feast-famine, high H/D, and without sludge pump for granulation.•Raw wastewater constituent aided in granulation was analyzed.•Bacterial community variations occurred in RFBR and SBR.A novel Reverse Flow Baffled Reactor (RFBR) was constructed to achieve aerobic granulation in continuous-flow process in order to treat the high quantity of influent wastewater. Municipal wastewater was fed to a 120 L reactor and successfully produced aerobic granules revealing a sludge volume index (SVI) of 33 mL/g. Aerobic granules possessed higher extracellular polymeric substances (EPS) content than seed sludge. The protein/polysaccharide (PN/PS) ratio in the EPS was determined to be about 10:1. Bacterial community analysis revealed that most of the species (Bacteroidetes, Nitrospira and Proteobacteria) found in the seed sludge were preserved in the reactor, except Pedobacter species that was washed out from the reactor. Moreover, different bacterial species were identified in RFBR and SBR (sequencing batch reactor) granules due to different process and operational parameters. Presence of Fe, Ca, Al, Si and P in wastewater were aggregated in granules (acted as a core) and enhanced the granulation. However, the RFBR was operated in periodic feast-famine condition, short settling time, high height/diameter (H/D) ratio, and without sludge return pump, which led to successful granulation in continuous-flow mode.

•The organic silicone wastewater was treated by FB-Fenton using three kind carriers.•Quartz sand was chosen as optimum carrier due to its better performance.•Optimum conditions were obtained to treat wastewater by orthogonal experiments.•FB-Fenton was better in oxidation and Fe3+ utilization than traditional Fenton.To achieve an enhanced degradation of recalcitrant organic silicone wastewater in the fluidized-bed Fenton process was attempted using three different carrier substrates [quartz sand, brick particles and granular activated carbon (GAC)]. Quartz sand was determined as the best carrier substrate due to better reactor bed expansion, fluidized state and pollutant removal rate than the brick particles and GAC. The iron oxide components such as FeOOH, FeO, Fe2O3, and Fe3O4 were found on the surface of coated quartz sand using X-ray diffraction (XRD) analysis. The optimal hydraulic retention time (HRT) of 60 min was determined based on COD and TOC removal rate. Further, the optimal operating conditions of pH 3.5, H2O2/COD (mass ratio) 2.6:1, H2O2/Fe2+ (molar ratio) 13.6:1 and quartz sand filling rate of 35% were determined by the orthogonal experiments for the recalcitrant treatment. In the fluidized-bed Fenton process treated effluent COD value was 40 mg/L and TOC value was 20 mg/L, with a removal rate of 95% and 85%, respectively. Compared to the traditional Fenton process the COD and TOC removal rates were found to increase by 20% and 15% respectively. Furthermore, the total iron removal rate was higher than conventional Fenton process, which significantly reduced the iron concentration in effluent.

Alum sludge from water treatment plant contained residual polyaluminum chloride (PACl) and large amount inorganic matters. Alum sludge acted as chemical conditioner and physical conditioner improved the sewage sludge dewatering. It indicated that the addition of alum sludge reduced the dosage of polyacrylamide (PAM) and decreased the moisture content of sewage sludge. The moisture content was 64% when the blend ratio was 1 kg/kg (dry alum sludge/dry sewage sludge) with plate-and-frame filter press. The 3D-excitation–emission matrix (3D-EEM) was used to analyze the sludge dewatering process. A mechanism hypothesis of adding alum sludge in sewage sludge for improving the sludge dewatering was proposed. Alum sludge implements the charge neutralization and adsorption bridging effect, provides friction and squeeze for crushing sludge particles even cell, and acts as skeleton builders in the sludge to improve the sludge dewatering.

Aerobic sludge granulation was rapidly obtained in the erlenmeyer bottle and sequencing batch reactor (SBR) using piggery wastewater. Aerobic granulation occurred on day 3 and granules with mean diameter of 0.2 mm and SVI30 of 20.3 mL/g formed in SBR on day 18. High concentrations of Ca and Fe in the raw piggery wastewater and operating mode accelerated aerobic granulation, even though the seed sludge was from a municipal wastewater treatment plant (WWTP). Alpha diversity analysis revealed Operational Taxonomic Units, Shannon, ACE and Chao 1 indexes in aerobic granules were 2013, 5.51, 4665.5 and 3734.5, which were obviously lower compared to seed sludge. The percentages of major microbial communities, such as Proteobacteria, Bacteroidetes and Firmicutes were obviously higher in aerobic granules than seed sludge. Chloroflexi, Planctomycetes, Actinobacteria, TM7 and Acidobacteria showed much higher abundances in the inoculum. The main reasons might be the characteristics of raw piggery wastewater and granule structure.Download high-res image (265KB)Download full-size image

Removing nitrogen from wastewater with low chemical oxygen demand/total nitrogen (COD/TN) ratio is a difficult task due to the insufficient carbon source available for denitrification. Therefore, in the present work, a novel sequencing batch biofilm reactor (NSBBR) was developed to enhance the nitrogen removal from wastewater with low COD/TN ratio. The NSBBR was divided into two units separated by a vertical clapboard. Alternate feeding and aeration was performed in the two units, which created an anoxic unit with rich substrate content and an aeration unit deficient in substrate simultaneously. Therefore, the utilization of the influent carbon source for denitrification was increased, leading to higher TN removal compared to conventional SBBR (CSBBR) operation. The results show that the CSBBR removed up to 76.8%, 44.5% and 10.4% of TN, respectively, at three tested COD/TN ratios (9.0, 4.8 and 2.5). In contrast, the TN removal of the NSBBR could reach 81.9%, 60.5% and 26.6%, respectively, at the corresponding COD/TN ratios. Therefore, better TN removal performance could be achieved in the NSBBR, especially at low COD/TN ratios (4.8 and 2.5). Furthermore, it is easy to upgrade a CSBBR into an NSBBR in practice.Download high-res image (268KB)Download full-size image