Effects of enhanced biological phosphorus removal on rapid control of sludge bulking and fast formation of aerobic granular sludge.

This study investigated the effects of enhanced biological phosphorus removal (EBPR) on rapid sludge bulking control and fast aerobic granular sludge (AGS) formation by adding 20 % of EBPR activated sludge to the bulking activated sludge (BAS) reactor. The results indicate that activating EBPR activity swiftly improved BAS settleability within 16 days, thus resolving sludge bulking issues. Subsequently, a settling time-based selection was employed, resulting in the BAS granulation within another 16 days. The rapid achievement of EBPR activity improved the BAS settleability and facilitated the formation of sludge aggregates, thereby expediting BAS granulation. Inhibition of filamentous bacteria and enrichment of slow-growing organisms contributed to both sludge bulking control and aerobic granulation. Furthermore, the increase in proteins/polysaccharides ratio facilitated the granulation process. Additionally, total nitrogen removal increased from 59.4 % to 71.7 % because of the mature AGS formation. This study provided an approach to simultaneously control sludge bulking and promote aerobic granulation.

Effect of polyethylene terephthalate particles on filamentous bacteria involved in activated sludge bulking and improvement in sludge settleability.

Excessive proliferation of filamentous bacteria within activated sludge leads to sludge structural instability and diminished settling properties, which is a prevalent issue in tannery wastewater treatment. Based on available information, there is a lack of research on the impact of particle addition on filamentous bacteria in activated sludge, specifically with respect to a reduction in sludge bulking. Therefore, polyethylene terephthalate (PET) was selected as the test material to elucidate the effect of particles on sludge bulking. The results illustrate that particles measuring 0.1 mm in diameter have a profound influence on both the quantity and morphological characteristics of filamentous bacteria in activated sludge. In an anaerobic-aoxic-oxic (AAO) reactor, the use of 4000 particles/L led to a significant decrease in the sludge volume index (SVI), reducing it from 358 mg/L to 198 mg/L. The results offer significant insights for resolving sludge bulking problems in tannery wastewaters. Moreover, the results are significant as a reference point for future investigations on the efficacy of incorporating diverse particulate materials to ameliorate issues associated with activated sludge bulking.

Filamentous Bacteria and Stalked Ciliates for the Stable Structure of Aerobic Granular Sludge Treating Wastewater.

Aerobic granular sludge (AGS) is a promising technology for wastewater treatment. AGS formation belongs to microbial self-aggregation. Investigation of the formation and stability of AGS is widely paid attention to, in particular the structure stability of large size granules. Two types of AGS were developed in two sequencing batch reactors fed by two different wastewaters, respectively. Through confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM), the structure and composition of granules were analyzed. Filamentous bacteria were observed in granules from synthetic wastewater reactor, while filamentous bacteria and stalked ciliates (Epistylis sp.) were simultaneously found in granules from domestic wastewater reactor. The analytic results show that filamentous bacteria and stalked ciliates acting as skeletons play important roles in the formation and stability of granules. With the bonding of extracellular polymeric substances (EPS), the filamentous bacteria and stalked ciliates could build bridges and frames to promote the aggregation of bacteria; these microorganisms could create a space grid structure around the surface layer of granules to enhance the strength of granules, and the remnants of the stalks could serve as supports to fix the steadiness of granules.

[Nanoscale Zero-valent Copper-Activated Molecular Oxygen for the Degradation of Enrofloxacin in Water].

Systematically studied the oxidation of enrofloxacin (ENR) in a nanoscale zero-valent copper (nZVC)-activated molecular oxygen system. The results show that nanoscale copper powder has a higher surface area than microscale copper powder, non-porous structure, and rough surface and exists in form of agglomerates. Nanoscale ZVC shows a superior activated performance toward molecular oxygen compared with microscale ZVC, which is due to its larger specific area and the fact that it corrodes easier. The H2O2 generated from the activation of molecular oxygen and the Cu+ released from surface corrosion form a novel Fenton-like system in which hydroxyl radicals are continuously produced, resulting in high-efficiency removal of ENR from water. The superoxide radicals produced during the reaction promote the reduction of Cu2+ to Cu+, thus speeding up the removal of ENR. The reaction conditions have a certain effect on the ENR degradation in nZVC-activated molecular oxygen systems. A higher nZVC dosage, lower ENR concentration, higher reaction temperature, and strong acidic conditions are favorable for the ENR removal.

Cultivating aerobic granular sludge in a developed continuous-flow reactor with two-zone sedimentation tank treating real and low-strength wastewater.

A continuous-flow reactor with two-zone sedimentation tank (CFR-TST) was developed to evaluate the formation of aerobic granular sludge (AGS). Micropowder made of excess sludge was added for a while in the CFR-TST, and selection pressure associated with settling time was created by the two-zone sedimentation tank. To avoid AGS disintegration, an airlift system for sludge return was used. The results show that AGS (mean particle size of 105µm; sludge volume index of approximately 26mL/g) was formed successfully in the CFR-TST. The micropowder induced bacterial attachment by acting as nuclei. The two-zone sedimentation tank made the well settling granules (i.e., heavy sludge) always retained in the CFR and poorly settling flocs (i.e., light sludge) washed away. After granulation, the contents of extracellular polymeric substances and metal precipitations in sludge increased, and the microbial community changed obviously. Additionally, the effluent concentrations of CODCr and NH4+-N were relatively low after granulation.

Nitrifying aerobic granular sludge fermentation for releases of carbon source and phosphorus: The role of fermentation pH.

The effect of fermentation pH (uncontrolled, 4 and 10) on the releases of carbon source and phosphorus from nitrifying aerobic granular sludge (N-AGS) was investigated. Meanwhile, metal ion concentration and microbial community characterization were explored during N-AGS fermentation. The results indicated that N-AGS fermentation at pH 10 significantly promoted the releases of soluble chemical oxygen demand (SCOD) and total volatile fatty acids (TVFAs). However, SCOD and TVFA released from N-AGS were inhibited at pH 4. Moreover, acidic condition promoted phosphorus release (mainly apatite) from N-AGS during anaerobic fermentation. Nevertheless, alkaline condition failed to increase phosphorus concentration due to the formation of chemical-phosphate precipitates. Compared with the previously reported flocculent sludge fermentation, N-AGS fermentation released more SCOD and TVFAs, possibly due to the greater extracellular polymeric substances content and some hydrolytic-acidogenic bacteria in N-AGS. Therefore, N-AGS alkaline fermentation facilitated the carbon source recovery, while N-AGS acidic fermentation benefited the phosphorus recovery.

Enhancing nitrogen removal from low carbon to nitrogen ratio wastewater by using a novel sequencing batch biofilm reactor.

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.

[Study on the 3D Fluorescence Feature of Styrene and Emergent Treatment of Styrene Pollutant in Water].

It has been acknowledged by WHO that styrene is a carcinogen which does great harm to human's health and natural environment. In recent years, given the frequency of the leakage accidents of styrene that has given rise to potential safety hazard to drinking water, the fast detection of styrene pollutant in water and treatment of accidental release are of great significance for supplying safe drinking water. Total scanning fluorescence technique was used to unravel the 3D fluorescence feature of styrene by scanning its aqueous solution. A distinct fluorescence peak of styrene located at Ex255/Em305 was detected. There was a significant linear correlation between the concentration of styrene and the value of fluorescence peak, the correlation index being 0.995 7. The color of the fluorescence peak got darker with the raise of styrene concentration. There were four conjugated double bonds existing in the structure of styrene, among which a cyclic hydrocarbon with a continuous pi bond exists in benzene ring, the other one is in vinyl. All carbon atoms that makes up the structure of styrene were in the same plane, thus styrene molecules were completely planar with certain rigidity, which is the feature of fluorescent substances. Therefore, the concentration of styrene and the pollution of water by the leakage of styrene could be easily detected with the 3D fluorescence spectra. Powdered activated carbon (PAC) had a good effect on the absorption of styrene dissolved in water. Adding PAC(180 mesh) at a dosage of 15 mg·L-1 into source water with the concentration of styrene was 0.02 mg·L-1, which is the limited value in sanitary standard for drinking water, the concentration could be reduced to 0.001 mg·L-1 and the removal rate of styrene was as high as 95.5% .

Aerobic granulation in a modified oxidation ditch with an adjustable volume intraclarifier.

A modified oxidation ditch (MOD) with an adjustable volume intraclarifier was proposed and used to achieve aerobic sludge granulation in continuous flow process. This MOD with working volume of 60L treated onsite wastewater from a town. Excellent aerobic granules with mean diameter of 600µm and sludge volume index (SVI) of 44mL/g were obtained in 120day. Bacterial community analysis revealed that most species from seed sludge were preserved in both MOD and granule SBR (G-SBR) except bacteria (Bacteroidetes) might be easily washed out during granulation. Some different bacterial communities were found in sludges from sequencing batch and continuous flow reactors. Presence of metal ions and inorganics in raw wastewater had positive effect on granule formation, but an adjustable volume intraclarifier for controlling selection pressure and deleting return sludge pump played a key role in aerobic sludge granulation.

Structure analysis of aerobic granule from a sequencing batch reactor for organic matter and ammonia nitrogen removal.

Aerobic granules were cultivated in a sequencing batch reactor (SBR). COD and ammonia nitrogen removal rate were 94% and 99%, respectively. The diameter, settling velocity and SVI10 of granules ranged from 2 to 5 mm, 80 to 110 m/h and about 40 mL/g, respectively. Freezing microtome images, DO concentration profiles by microelectrode, distribution of bacteria and EPS by confocal laser scanning microscopy (CLSM) show that the aerobic granules have a three-layer structure. Each layer has different thickness, character, bacteria, and DO transfer rate. A hypothesis for granule structure is proposed: the first layer, the surface of the granule, is composed mostly of heterotrophic organisms for organic matter removal, with a thickness range from 150 to 350 µm; the second layer, mostly composed of autotrophic organisms for ammonia nitrogen removal, with a thickness range from 250 to 450 µm; the third layer, located in the core of the granule, has mostly an inorganic composition and contains pores and channels.