Xiangchun Quan

Distributions of polycyclic aromatic hydrocarbons in the Daliao River Estuary of Liaodong Bay, Bohai Sea (China).

The distributions of 16 polycyclic aromatic hydrocarbons (PAHs) were determined in the aqueous phase, suspended particulate matter (SPM), sediment, and pore water of the Daliao River Estuary in Liaodong Bay, Bohai Sea (China). Total PAH concentrations ranged from 139.16 to 1717.87ngL(-1) in surface water, from 226.57 to 1404.85ngL(-1) dry weight in SPM, from 276.26 to 1606.89ngg(-1) dry weight in sediments, and from 10.20 to 47.27microgL(-1) in pore water. PAH concentrations were at relatively moderate levels in water, SPM, sediment and pore water in comparison with those reported for other estuary and marine systems around the world. Sedimentary PAH concentrations decreased offshore owing to active deposition of laterally-transported river-borne particles. PCA analysis of the possible PAH source suggested petrogenic and pyrolytic PAH inputs in the studied region.

Biodegradation of 2,4-dichlorophenol in sequencing batch reactors augmented with immobilized mixed culture

2,4-Dichlorophenol (2,4-DCP) degrading mixed culture was immobilized in polyvinyl alcohol jel beads and supplemented to sequencing batch reactors (SBR) to treat 2,4-DCP containing wastewater. Impacts of bioaugmentation level on the performance of bioaugmented systems were studied. Results show that inoculum size affected the start-up time of the SBR systems. For the non-augmented SBR system, nine days was needed for the system to start-up, whereas it only took six, four, three and two days for the SBRs with 1.9%, 3.7%, 5.6% and 9.3% immobilized culture, respectively. In addition, bioaugmented SBR systems demonstrated stronger capacity to cope with high 2,4-DCP shock loading than the control system. The control SBR failed to treat 2,4-DCP at 166 mg/l in influent, while the SBR with 1.9% inoculation could successfully cope with 2,4-DCP at 166 mg/l, but failed at 250 mg/l, and the SBR with 3.7%, 5.6% and 9.3% immobilized culture could successfully degrade 250 mg/l 2,4-DCP in feed. Furthermore, the contributions to the removal of 2,4-DCP by the introduced and indigenous culture in an augmented SBR system at various operation stages were investigated. It was found that augmented culture played the primary role in degrading 2,4-DCP at the beginning of system start-up, but after one-month operation, both the indigenous and the introduced culture posed strong ability to degrade 2,4-DCP.

Biodegradation of 2,4-dichlorophenol and phenol in an airlift inner-loop bioreactor immobilized with Achromobacter sp

An airlift inner-loop bioreactor packed with honeycomb-like ceramic as the carrier was developed and its capacity to immobilize microorganism was studied through adding bacteria, Achromobactersp., capable of degrading 2,4-dichlorophenol (2,4-DCP), directly to the reactor under continuous operation. Effects of phenol in the feed with 2,4-DCP on 2,4-DCP removal were investigated under fed-batch and continuous operations. The results showed that the pure strain could be easily immobilized on the carrier and proliferated using 2,4-DCP as the sole carbon source. In the process of fed-batch operation, removal rate of 2,4-DCP decreased with the increase in run number, while that of phenol was just to the contrary. In the continuous operation, 2,4-DCP loading rate was kept at 29.72‐32.23 mg/(l day), but phenol loading rate was increased stepwise from 325.56 to 602.79 mg/(l day). The results showed that with the increase of phenol loading rates, the removal efficiency of 2,4-DCP declined from 100 to 87.9%, while that of phenol remained at about 99.6%. Presence of phenol in feed inhibited the biodegradation of 2,4-DCP and caused the major carbon source shift from 2,4-DCP to phenol.

Distribution, partitioning and sources of polycyclic aromatic hydrocarbons in Daliao River water system in dry season, China.

Eighteen polycyclic aromatic hydrocarbons (PAHs) were analyzed in 29 surface water, 29 suspended particulate matter (SPM), 28 sediment, and 10 pore water samples from Daliao River water system in dry season. The total PAH concentration ranged from 570.2 to 2318.6 ng L(-1) in surface water, from 151.0 to 28483.8 ng L(-1) in SPM, from 102.9 to 3419.2 ng g(-1) in sediment and from 6.3 to 46.4 microg l(-1) in pore water. The concentration of dissolved PAHs was higher than that of particulate PAHs at many sites, but the opposite results were generally observed at the sites of wastewater discharge. The soluble level of PAHs was much higher in the pore water than in the water column. Generally, the water column of the polluted branch streams contained higher content of PAHs than their mainstream. The environmental behaviors and fates of PAHs were examined according to some physicochemical parameters such as pH, organic carbon, SPM content, water content and grain size in sediments. Results showed that organic carbon was the primary factor controlling the distribution of the PAHs in the Daliao River water system. Partitioning of PAHs between sediment solid phase and pore water phase was studied, and the relationship between logK(oc) and logK(ow) of PAHs on some sediments and the predicted values was compared. PAHs other than naphthalene and acenaphthylene would be accumulated largely in the sediment of the Dalaio River water system. The sources of PAHs were evaluated employing ratios of specific PAHs compounds and different wastewater discharge sources, indicating that combustion was the main source of PAHs input.

Aliphatic and polycyclic aromatic hydrocarbons in the Xihe River, an urban river in China's Shenyang City: distribution and risk assessment.

The characteristics of petroleum hydrocarbons and the risks they pose to the ecosystem were studied in the Xihe River, which is an urban river located in Shenyang, China. High levels of aliphatic hydrocarbons (AHc) and polycyclic aromatic hydrocarbons (PAHs) were observed in the river due to the discharge of wastewater from industrial and municipal facilities for a long period of time. High-molecular-weight hydrocarbons, including unresolved complex mixtures (UCM) of n-alkanes between n-C16 and n-C32 and of PAHs with four to six rings, were the dominant hydrocarbons in the river, particularly in suspended particulate matter (SPM) and sediments. The AHc was mainly from petrogenic sources, whereas PAHs was from both pyrolytic and petrogenic source inputs. Our results suggest that there is a high risk of toxicity for the soils and groundwater of the study area. The overall toxicity in the sediments can be described using the toxic equivalent (TEQ) of dibenzo[a,h]anthracene (DBA) based on benzo(a)pyrene (TEQ(BaP)) and dioxins (TEQ(TCDD)) toxic equivalent concentrations. The TEQ values for benzo(a)pyrene (TEQ(BaP)) and dioxins (TEQ(TCDD)) presented a consistent assessment of sediment PAHs.

Removal of 2,4-dichlorophenol in a conventional activated sludge system through bioaugmentation

For the removal of toxic and recalcitrant organic substances intermittently appearing in wastewater, bioaugmentation with bacteria having specific degradation ability could be a powerful tool to improve the treatment process. 2,4-Dichlorophenol (2,4-DCP) was chosen as the target recalcitrant substance and a 2,4-DCP degrading special mixed culture was used as bioaugmentation microorganisms. The feasibility and strategies to combine bioaugmentation into a conventional activated sludge (CAS) system in terms of enhancing its efficiency and reliability was investigated. Results showed that for domestic wastewater with multiple chlorophenols, bioaugmentation with a 2,4-DCP degrading culture in a CAS system not only enhanced the removal of 2,4-DCP effectively, but also improved the removal of other chlorophenols such as 4-monochlorophenol (4-MCP) and 2,4,5-trichlorophenol (2,4,5-TCP). A separate bioaugmented bioreactor was combined into the original CAS system at different locations and the effects of the bioaugmentation location on the performance of the combined biotreatment process were studied. Results indicated that the CAS-Bioaug system, in which the bioaugmented bioreactor was set at a location after the original CAS reactor, performed better than the Bioaug-CAS system, in which the bioaugmented bioreactor was placed before the original CAS reactor. Bioaugmentation could be used as an effective and efficient method to improve a CAS process facing sudden toxic pollutant shock loading.

Responses of anaerobic granule and flocculent sludge to ceria nanoparticles and toxic mechanisms.

Effects of CeO2-NPs on anaerobic fermentation were investigated from the processes of acidification and methanation with anaerobic granule sludge and anaerobic flocculent sludge as the targets. Results showed that acidification process was more sensitive to CeO2-NPs than methanation process. Both types of sludge produced less short-chain fatty acid compared to the control, with a reduction of 15-19% for the flocculent sludge at the dosage of 5, 50 and 150 mg CeO2-NPs/g-VSS, and a reduction of 35% for the granular sludge at 150 mg CeO2-NPs/g-VSS. CeO2-NPs caused no inhibition to methanation process. Most of CeO2-NPs distributed on the surface of sludge as revealed by fluorescence labeled CeO2-NPs. The toxicity of CeO2-NPs to anaerobic sludge did not result from reactive oxygen species. Physical penetration and membrane reduction may be important toxic mechanisms.

Bioaugmentation of aerobic sludge granules with a plasmid donor strain for enhanced degradation of 2,4-dichlorophenoxyacetic acid.

Aerobic sludge granules pre-grown on glucose were bioaugmented with a plasmid pJP4 carrying strain Pseudomonas putida SM1443 in a fed-batch microcosm system and a lab-scale sequencing batch reactor (SBR) to enhance their degradation capacity to 2,4-dichlorophenoxyacetic acid (2,4-D). The fed-batch test results showed that the bioaugmented aerobic granule system gained 2,4-D degradation ability faster and maintained a more stable microbial community than the control in the presence of 2,4-D. 2,4-D at the initial concentration of about 160 mg/L was nearly completely removed by the bioaugmented granule system within 62 h, while the control system only removed 26% within 66 h. In the bioaugmented SBR which had been operated for 90 days, the seeded aerobic granules pre-grown on glucose successfully turned into 2,4-D degrading granules through bioaugmentation and stepwise increase of 2,4-D concentration from 8 to 385 mg/L. The granules showed a compact structure and good settling ability with the mean diameter of about 450 microm. The degradation kinetics of 2,4-D by the aerobic granules can be described with the Haldane kinetics model with V(max)=31.1 mg 2,4-D/gVSS h, K(i)=597.9 mg/L and K(s)=257.3 mg/L, respectively. This study shows that plasmid mediated bioaugmentation is a feasible strategy to cultivate aerobic granules degrading recalcitrant pollutants.

Nitrous oxide emission and nutrient removal in aerobic granular sludge sequencing batch reactors

Application of aerobic granular sludge into wastewater treatment is promising due to its excellent settling ability and high microbial concentrations. However, its spatial structure could induce incomplete denitrification, leading to generation of nitrous oxide (N(2)O) - a potent greenhouse gas. Under the temperature of 14 ± 4 °C, three identical laboratory-scale aerobic granular sludge sequencing batch reactors (SBRs) were established to treat synthetic wastewater simulating a mixture of liquid pig manure digestate and municipal wastewater at three aeration rates (0.2, 0.6 and 1.0 L air/min) and three COD:N ratios (1:0.22, 1:0.15 and 1:0.11). The studies show the proportions of N(2)O emission to the influent nitrogen loading rate at the aeration rates of 0.2, 0.6 and 1.0 L air/min were 8.2%, 6.1% and 3.8% at a COD:N ratio of 1:0.22; 7.0%, 5.1% and 3.5% at a COD:N ratio of 1:0.15; and 4.4%, 2.9% and 2.2% at a COD:N ratio of 1:0.11, respectively. With NO(2)(-) as the only nitrogen source in the liquid phase, the specific N(2)O generation rates via denitrification were 1.7, 1.6 and 1.3 μg N(2)O/(g SS· min) at the aeration rates of 0.2, 0.6 and 1.0 L air/min, respectively, which were 40.9%, 44.8%, 39.9% higher than those with NO(3)(-) as the only nitrogen source, respectively. N(2)O generation by aerobic granular sludge due to NH(4)(+)-N nitrification was not sensitive to the aeration rate, and the average specific N(2)O generation rate was 0.8 ± 0.02 μg N(2)O/(g SS· min).

Comparison of polycyclic aromatic hydrocarbons in sediments from the Songhuajiang River (China) during different sampling seasons

The Songhuajiang River watershed is the important industrial and foodstuff base in the northeast part of China. However, the increasing population, industrial and agricultural activities around the Songhuajiang River lead to the introduction of contaminants and the possibility of polluting the river. This investigation represents an extensive study of the spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in the sediment samples collected from the Songhuajing River in flood season (August, 2005) and icebound season (December, 2005) by using the gas chromatography-mass spectrometry (GC/MS) analyses. In flood season, the total PAHs concentrations in sediments ranged from 84.44 ng g−1 to 14938.73 ng g−1, with average concentration of 2430.37 ng g−1. In icebound season, the total PAHs concentrations in sediments ranged from 23.61 ng g−1 to 15310.25 ng g−1, with average concentration of 1825.60 ng g−1. Compared to the concentration of PAHs between central sediment and riverbank-exposed sediment at some stations, the concentration in exposed sediment was higher than that in the central sediment in the upstream of river. It was also observed that the concentration of PAHs in flood season was higher than that in icebound season. The level of PAHs in the sediments of Songhua River was higher in comparison with values reported from other river and marine systems in the world. The most contaminated sediment samples were found in the upstream area of Songhuajiang River located near Jilin petrochemical industrial company for both flood and icebound seasons. The 4–6 ring PAHs were dominated in sediments due to their higher persistence. There was positive correlation between total PAHs concentration in sediment samples and TOC or LOI (r = 0.62 and r = 0.58, P < 0.01, n = 31). The calculated ratio of selected PAH and principal component analysis (PCA) suggests the contamination source of PAHs were combined inputs of pyrolytic and petrogenic contamination, due to the discharge from municipal and industrial wastewater runoff and atmospheric fallout.