Chaoxiang Liu

Elimination of veterinary antibiotics and antibiotic resistance genes from swine wastewater in the vertical flow constructed wetlands.

This paper investigated the efficiency of two vertical flow constructed wetlands characterized by volcanic (CW1) and zeolite (CW2) respectively, at removing three common antibiotics (ciprofloxacin HCl, oxytetracycline HCl, and sulfamethazine) and tetracycline resistance (tet) genes (tetM, tetO, and tetW) from swine wastewater. The result indicated that the two systems could significantly reduce the wastewater antibiotics content, and elimination rates were in the following sequence: oxytetracycline HCl>ciprofloxacin HCl>sulfamethazine. The zeolite-medium system was superior to that of the volcanic-medium system vis-à-vis removal, perhaps because of the differing pH values and average pore sizes of the respective media. A higher concentration of antibiotics accumulated in the soil than in the media and vegetation, indicating that soil plays the main role in antibiotics removal from wastewater in vertical flow constructed wetlands. The characteristics of the wetland medium may also affect the antibiotic resistance gene removal capability of the system; the total absolute abundances of three tet genes and of 16S rRNA were reduced by 50% in CW1, and by almost one order of magnitude in CW2. However, the relative abundances of target tet genes tended to increase following CW1 treatment.

Behavior of tetracycline and sulfamethazine with corresponding resistance genes from swine wastewater in pilot-scale constructed wetlands

Four pilot-scale constructed wetlands (free water surface, SF; horizontal subsurface flow, HSF; vertical subsurface flows with different water level, VSF-L and VSF-H) were operated to assess their ability to remove sulfamethazine (SMZ) and tetracycline (TC) from wastewaters, and to investigate the abundance level of corresponding resistance genes (sulI, sulII, tetM, tetW and tetO) in the CWs. The results indicated that CWs could significantly reduce the concentration of antibiotics in wastewater, and the mass removal rate range of SMZ and TC were respectively 11%-95% and 85%-95% in the four systems on the basis of hydraulic equilibrium; further relatively high removal rate was observed in VSF with low water level. Seasonal condition had a significant effect on SMZ removal in the CWs (especially SMZ in SF), but TC removal in VSFs were not considered to have statistically significant differences in winter and summer. At the end period, the relative abundances of target genes in the CWs showed obvious increases compared to initial levels, ranging from 2.98 × 10(-5) to 1.27 × 10(-1) for sul genes and 4.68 × 10(-6) to 1.54 × 10(-1) for tet genes after treatment, and those abundances showed close relation to both characteristic of wastewater and configuration of CWs.

Development of algae-bacteria granular consortia in photo-sequencing batch reactor

The development and properties of algae-bacteria granular consortia, which cultivated with the algae (Chlorella and Scenedesmus) and aerobic granules, was investigated in this experiment. The results indicated that the granular consortia could be successfully developed by selection pressure control, and the algal biomass and extracellular polymeric substances (EPS) concentration in the consortia showed notable correlation with the operating parameters of reactor. The maximum specific removal rates of total nitrogen and phosphate were obtained from the granular consortia with the highest algal biomass, yet the correlation between the fatty acid methyl esters yield and the algal biomass in the consortia was not markedly observed. The seed algae maintained dominance in the phototroph community, whereas the cyanobacteria only occupied a small proportion (5.2-6.5%). Although the bacterial communities with different operational strategies showed significant difference, the dominated bacteria (Comamonadaceae, 18.79-36.25%) in the mature granular consortia were similar.

Recent Developments and Future Perspectives of Anaerobic Baffled Bioreactor for Wastewater Treatment and Energy Recovery

Anaerobic baffled reactor (ABR) processes play an increasingly important role in wastewater treatment and resource recycling by its ingenious construction and excellent performance. The authors aim to introduce new research progresses and applications of ABR in the last two decades, focusing mainly on the following aspects: presenting and comparing its development and application instances, discussing the optimization of operating regulation and mathematical models, stating existing problems in current researches, suggesting possible improvements, and proposing future research perspectives. The contributions of this review involve enhancing ABR treatment efficiency and operation stability to provide information for colleagues.

An integrated algorithm for estimating regional latent heat flux and daily evapotranspiration

Using remote‐sensing data and ground‐based data, we constructed an integrated algorithm for estimating regional surface latent heat flux (LE) and daily evapotranspiration (ET d). In the algorithm, we first used trapezoidal diagrams relating the surface temperature and fractional vegetation cover (f c) to calculate the surface temperature–vegetation cover index, a land surface moisture index with a range from 0.0 to 1.0. We then revised a sine function to assess ET d from LE estimated for the satellites overpass time. The algorithm was applied to farmland in the North China Plain using Landsat Thematic Mapper (TM)/Enhanced Thematic Mapper Plus (ETM+) data and synchronous surface‐observed data as inputs. The estimated LE and ET d were tested against measured data from a Bowen Ratio Energy Balance (BREB) system and a large‐scale weighing lysimeter, respectively. The algorithm estimated LE with a root mean square error (RMSE) of 50.1 W m−2 as compared to measurements with the BREB System, and ET d with an RMSE of 0.93 mm d−1 as compared with the measurement by the lysimeter. Sensitivity analysis showed that changing meteorological variables have some influence on LE, while variation of f c has little effect on LE. The test of the model in the study indicated that the improved algorithm provides an accurate and easy‐to‐handle approach for assessing regional surface LE and ET d. Further improvement can be achieved in the assessments if we increase the accuracy of some key parameters on a large regional scale, such as the minimum stomatal conductance and the atmospheric vapour pressure deficit.

Fermentative hydrogen production from beet sugar factory wastewater treatment in a continuous stirred tank reactor using anaerobic mixed consortia

A low pH, ethanol-type fermentation process was evaluated for wastewater treatment and bio-hydrogen production from acidic beet sugar factory wastewater in a continuous stirred tank reactor (CSTR) with an effective volume of 9.6 L by anaerobic mixed cultures in this present study. After inoculating with aerobic activated sludge and operating at organic loading rate (OLR) of 12 kgCOD·m−3·d−1, HRT of 8h, and temperature of 35°C for 28 days, the CSTR achieved stable ethanol-type fermentation. When OLR was further increased to 18 kgCOD·m−3·d−1 on the 53rd day, ethanol-type fermentation dominant microflora was enhanced. The liquid fermentation products, including volatile fatty acids (VFAs) and ethanol, stabilized at 1493 mg·L−1 in the bioreactor. Effluent pH, oxidation-reduction potential (ORP), and alkalinity ranged at 4.1–4.5, −250-(−290) mV, and 230–260 mgCaCO3·L−1. The specific hydrogen production rate of anaerobic activated sludge was 0.1 L·gMLVSS−1·d−1 and the COD removal efficiency was 45%. The experimental results showed that the CSTR system had good operation stability and microbial activity, which led to high substrate conversion rate and hydrogen production ability.

Study of oyster shell as a potential substrate for constructed wetlands

We tested the suitability of oyster shell (OS) as a substrate for phosphorus removal in constructed wetlands (CWs) treating swine wastewater. OS is proven to have a significant phosphorus adsorption capacity; significant phosphorus removal was achieved in vertical subsurface flow constructed wetlands (VSSFs) that were filled with OS and used to treat swine wastewater. In the VSSF system, OS adsorption and precipitation played the greatest role in phosphorus removal, and the phosphorus distribution in the substrate layers was attributed to the vertical flow state of wastewater in the system. Ca-P was the predominant form of phosphorus in the system. Overall, the study results showed that OS could be used for phosphorus removal in CWs. OS also allowed for reuse of a waste substance, making the overall system more environmentally friendly.

Treatment of swine wastewater in aerobic granular reactors: comparison of different seed granules as factors

The granulation process, physic-chemical properties, pollution removal ability and bacterial communities of aerobic granules with different feed-wastewater (synthetic wastewater, R1; swine wastewater, R2), and the change trend of some parameters of two types of granules in long-term operated reactors treating swine wastewater were investigated in this experiment. The result indicated that aerobic granulation with the synthetic wastewater had a faster rate compared with swine wastewater and that full granulation in R1 and R2 was reached on the 30th day and 39th day, respectively. However, although the feed wastewater also had an obvious effect on the biomass fraction and extracellular polymeric substances of the aerobic granules during the granulation process, these properties remained at a similar level after long-term operation. Moreover, a similar increasing trend could also be observed in terms of the nitrogen removal efficiencies of the aerobic granules in both reactors, and the average specific removal rates of the organics and ammonia nitrogen at the steady-state stage were 35.33 mg•g–1 VSS and 51.46 mg•g–1 VSS for R1, and 35.47 mg•g–1 VSS and 51.72 mg•g–1 VSS for R2, respectively. In addition, a shift in the bacterial diversity occurred in the granulation process, whereas bacterial communities in the aerobic granular reactor were not affected by the seed granules after long-term operation.

Simultaneous production of bio-hydrogen and methane from soybean protein processing wastewater treatment using anaerobic baffled reactor (ABR)

AbstractBio-hydrogen (H2) and methane (CH4) co-production from soybean protein processing wastewater (SPPW) was examined using a four-compartment anaerobic baffled reactor (ABR) with the active reactor volume (34 L) under continuous flow condition in this present study. At steady state, the ABR achieved H2 yields of 25.67 L/d, specific hydrogen production rate of anaerobic activated sludge was 0.28  L/g MLVSS d, CH4 yields of 13.89 L/d, and chemical oxygen demand (COD) removal of 95% when operated at the organic loading rate of 1.9–2.6 kg COD/m3 d, hydraulic retention time of 48 h, and temperature of (35 ± 1) °C, respectively. The results showed that the niches of the bio-hydrogen-producing phase and the methane-producing phase in the ABR are different. A high alkalinity in the methanogenic compartment of the ABR was able to secure the pH neutral and methane generation. In general, the ABR proved to be a stable, reliable, and effective process for energy recovery and stabilization treatment of SPPW.

Comparison of nutrient removal and bacterial communities between natural zeolite-based and volcanic rock-based vertical flow constructed wetlands treating piggery wastewater

abstract This study designed two vertical flow constructed wetlands (VFCW) as a secondary treatment for piggery wastewater. The effect of effluent recirculation and substrate type on treatment efficiency of constructed wetlands on piggery waster was firstly investigated. Recirculation considerably improved the removal of NH4-N, total nitrogen (TN), and total phosphorus (TP), but not that of chemical oxygen demand (COD). The natural zeolite-based VFCW performed better than volcanic rock-based VFCW for all four parameters. At the highest recirculation ratio, the average treatment efficiencies of natural zeolite-based VFCW reached 50.7, 91.6, 48.3, and 80.7% for COD, NH4-N, TN, and TP, respectively. The diversity and composition of total bacteria and ammonia-oxidizing bacteria (AOB) in the bioflim of natural zeolite and volcanic rock were then determined. Both total bacteria and AOB in biofilm of natural zeolite were more diverse than those in biofilm of volcanic rock. Phylogenetic analyses further revealed ...