Guodong Ji

Quantitative response relationships between nitrogen transformation rates and nitrogen functional genes in a tidal flow constructed wetland under C/N ratio constraints.

The present study explored treatment performance and nitrogen removal mechanisms of a novel tidal flow constructed wetland (TF CW) under C/N ratios ranging from two to 12. High and stable COD (83-95%), [Formula: see text] (63-80%), and TN (50-82%) removal efficiency were simultaneously achieved in our single-stage TF CW without costly aeration. Results showed that a C/N ratio exceeding six was required to achieve complete denitrification without [Formula: see text] and [Formula: see text] accumulation in the system. Molecular biological analyses revealed aerobic ammonia oxidation was the dominant [Formula: see text] removal pathway when the C/N ratio was less than or equal to six. However, when the C/N ratio was greater than six, anammox was notably enhanced, resulting in another primary [Formula: see text] removal pathway, in addition to the aerobic ammonia oxidation. Quantitative response relationships between nitrogen transformation rates and nitrogen functional genes were established, and these relationships confirmed that different nitrogen transformation processes were coupled at the molecular level (functional genes), and collaboratively contributed to nitrogen removal in the TF CW. Specifically, [Formula: see text] transformation rates were collectively determined by amoA, nxrA, anammox, narG, nirS, nirK, and nosZ; and TN removal was influenced primarily by amoA and anammox.

Constructed subsurface flow wetland for treating heavy oil-produced water of the Liaohe Oilfield in China

Abstract A pilot subsurface flow constructed wetland (CW) has been constructed in the Liaohe Delta, China to treat heavy oil-produced water with large amounts of dissolved recalcitrant organic compounds. Pollutant concentrations and change of wetland plants were periodically monitored. Treatment effectiveness was evaluated and indicated high mean removal efficiencies, 81% for chemical oxygen demand (COD), 89% for biochemical oxygen demand (BOD 5 ), 89% for mineral oil, and 81% for total Kjeldahl nitrogen (TKN) achieved in reed bed#2, to produce wetland effluent average concentrations with COD 77 mg l −1 , BOD 5 3.5 mg l −1 , TKN 2.2 mg l −1 , and mineral oil 2.9 mg l −1 . We observed that during the vegetation growth period there was no influence of heavy oil-produced water on the numbers of leaves of reeds in CW, whereas, the biomasses and heights of reeds showed significant loss with increasing hydraulic loading. The heavy oil-produced water had no obvious effect on the reed indices of cellulous, lignin, pentose and the length/width ratio of cellulose.

Anaerobic baffled reactor (ABR) for treating heavy oil produced water with high concentrations of salt and poor nutrient

The start-up and operational performance (total 212 days, including the start-up of 164 days) of an anaerobic baffled reactor (ABR), which is used to treat heavy oil produced water, was studied without the temperature control. Inoculums were mixtures of acclimated sediment taken from a heavy oil produced water treatment plant and digested sludge from a sewage wastewater treatment plant. The rod-shaped and spherical granules with colors of henna and black, in which Clostridia, Methanosarcina and Methanothrx sp. were main populations, were observed in each compartment of ABR after the reactors successful start-up (day 164). Rhodopseudomonas with the activity of lipase and halotolerant, as a kind of photosynthetic bacteria, was also observed in the first five compartments. X-ray diffraction (XRD) showed that the spherical granule sludge was compact and contained a large amount of organics, amorphous materials, and crystals of Fe(2)O(3), FeS, and CaCO(3), whereas the rod-shaped granule sludge was incompact without crystals of Fe(2)O(3), FeS, and CaCO(3). Scanning electron microscope (SEM) showed that the skeleton construction of this rod-shaped granule was filamentous bacteria and amount of extracellular polymeric substances (EPS). The ABR, after successful start up, can achieve high average chemical oxygen demand (COD) and oil removals of 65% and 88% for heavy oil produced water with poor nutrient (COD:TN:TP, 1200:15:1) and high salt concentration (1.15-1.46%), respectively. Furthermore, ABR kept stable during 2.5 times the COD level shock load (0.50 kg COD m-3 d-1) for four days.

QSAR study of the toxicity of benzoic acids to Vibrio fischeri, Daphnia magna and carp.

The toxicities of benzoic acids to Vibrio fischeri, Daphnia magna and carp were measured. The results showed that the toxicity to V. fischeri and Daphnia decreased in the order of bromo > chloro > fluoro approximately equal to aminobenzoic acids. The toxicity of substituted benzoic acids to carp and Daphnia was much lower that to V. fischeri. The results also showed that the toxicity of benzoic acids to Daphnia decreased as the pH increased. It is suggested that ionized and non-ionized forms have different toxic responses. The non-ionized form may play an important role in toxicity because the toxicity of benzoic acids to Daphnia greatly decreases as the pH increases. The toxicity of benzoic acids to Daphnia may operate through non-polar narcosis, based on the regression results between the toxicities and partition coefficients (log P) and apparent partition coefficients (log D). However, toxicity cannot be predicted from non-polar baseline models because the ionized and non-ionized form of benzoic acids have different contributions to toxicity. Compared with the single descriptors, the prediction of toxicity of the benzoic acids was improved remarkably by using log P with pKa and log P with ELUMO. For the toxicity of benzoic acids to V. fischeri, it is suggested that the toxic mechanism may be different from the mechanism in Daphnia and carp. A probable reason is that V. fischeri is a unicellular organism with low lipid content, and hence both ionized and non-ionized forms of benzoic acids can easily cross the cell membrane and contribute to toxicity.

Washing of field weathered crude oil contaminated soil with an environmentally compatible surfactant, alkyl polyglucoside

Weathered crude oil contaminated soils (COCSs), which are much more difficult to remediate than those freshly contaminated, are widespread especially at the sites of oil fields and industries. Surfactant enhanced ex situ soil washing could be used to remediate COCSs, but surfactant toxicity becomes one of the major concerns. In this study, a class of green surfactants, alkyl polyglucosides (APGs), were tested in washing the field weathered COCS with relatively high oil concentration (123 mgg(-1) dry soil) from Jilin Oilfield, Northeastern China. APG1214, characterized with longer alkyl chain, was more effective than APG0810 in crude oil removal. Adding inorganic sodium salts into APG1214 solution further improved the crude oil removal efficiency (CORE). Washing parameters (temperature, washing time, agitation speed and solution/soil ratio) were investigated and further optimized integratedly with an orthogonal design. At the optimum conditions, the CORE reached 97%. GC/MS analysis showed that the proportion of small n-alkanes (C(16)-C(23)) in residual crude oil gradually increased, which was helpful to interpret the oil removal mechanism. Moreover, eminent effect on removal of large n-alkanes was achieved from the synergy between APG1214 and inorganic salts, which was opposite to the effect when they were added separately. This study demonstrated a promising way to remediate COCS with ecologically compatible surfactant and provided guidelines for its practical application.

Bacterial community structure and dominant bacteria in activated sludge from a 70 °C ultrasound-enhanced anaerobic reactor for treating carbazole-containing wastewater

Status of, and changes in, the bacterial communities at two acclimation stages (with- and without-ultrasound) in a small 70 degrees C ultrasound-enhanced anaerobic reactor for treating carbazole-containing wastewater reactor were analyzed by PCR-DGGE and real-time PCR techniques. PCR-DGGE results indicated that a large number of bands occurred in the whole sludge samples. Pseudomonas sp., Comamonas sp., and Diaphorobacter sp. were identified as being able to utilize carbazole as a carbon source, survive in an anaerobic and ultra-high-temperature environment and become dominant bacterial taxa during the with-ultrasound stage in the reactor. Total bacterial density in the with-ultrasonic stages was 10 x higher than in the without-ultrasonic treatment. The proportion of Pseudomonas was relatively stable at 0.13%-0.15% in both acclimation stages, which indicates that Pseudomonas can flourish and promote carbazole degradation either with or without-ultrasound. These studies provide information on carbazole degradation under ultra-high-temperature conditions in an anaerobic environment.

Wastewater treatment efficiency of a multi-media biological aerated filter (MBAF) containing clinoptilolite and bioceramsite in a brick-wall embedded design

A multi-media biological aerated filter (MBAF) with clinoptilolite media was used to treat synthetic wastewater. Coal ash bioceramsite with supplemental metallic iron was added to the clinoptilolite media of MBAFs in a brick-wall embedded design. Performance parameters, such as hydraulic, organic, N and P loading capacity and microbial community composition were studied for different quantity of supplemental metallic iron contained in three MBAFs. The MBAFs with more metallic iron were found to have superior hydraulic and organic loading, and higher N and P capacities. COD, NH3-N and TP removal dropped by 7-10%, 6-7% and 4-5%, respectively, with when hydraulic loading was raised from 2.8 to 7.5 m3 m(-2) d(-1). NH3-N removal also decreased 8-9% when ammonia loading was elevated from 0.078 to 0.156 kg NH3-N m(-3) d(-1). Real-time PCR revealed a relatively stable bacterial community composed primarily of eubacteria that formed after an initial 120 d operational period. Doubling the amount of metallic iron in the bioceramsite media resulted in a twofold increase of eubacteria in the MBAF, but a decrease in the ratio of anaerobic ammonia-oxidizing bacteria to total bacteria.

Quantitative structure-activity relationships of nitroaromatic compounds to four aquatic organisms☆

Abstract Quantitative structure-activity relationships of 26 nitroaromatic compounds to guppy ( Poecilia reticulata ), carp ( Cyprinus carpio), Scenedesmus obliguus, Daphnia carinata were studied based on equations we established. Results showed that observed toxicity of chemicals could be estimated by the parameters of halfwave reduction potential ( E 1 2 ) and bioconcentration factor (BCF). The toxicity data of nitroaromatic compounds to four aquatic organisms were estimated by these parameters. Compared with octanol/water partition coefficient method, the LC 50 values predicted by the two parameters are close to observed LC 50 values. Regression results also showed that the highest occupied molecular orbital energy (E HOMO ), the lowest unoccupied molecular orbital energy (E LUMO ) and octanol/water partition coefficient (K OW ) were ideal parameters instead of the reaction equilibrium constant of target molecule-organic chemical in target cells (K) and bioconcentration factor. Relationships between the toxicity data of guppy, carp, Scenedesmus obliguus, Daphnia carinata and the parameters of E HOMO , E LUMO and K OW were analyzed. Predicted and observed LC 50 values are in good agreement. The observed toxicity data of 2,4-dinitrotoluene and 2,6-dinitrotoluene may be lower than the expected toxicity data because the photolysis of the two chemicals is rapid during the course of experiments.

Assessing nitrogen transformation processes in a trickling filter under hydraulic loading rate constraints using nitrogen functional gene abundances.

A study was conducted of treatment performance and nitrogen transformation processes in a trickling filter (TF) used to treat micro-polluted source water under variable hydraulic loading rates (HLRs), ranging from 1.0 to 3.0 m(3)/m(2) d. The TF achieved high and stable COD (97.7-99.3%) and NH4(+)-N (67.3-92.7%) removal efficiencies. Nitrification and anaerobic ammonium oxidation were the dominant nitrogen removal processes in the TF. Path analysis indicated that amoA/anammox and amoA/(narG+napA) were the two key functional gene groups driving the major processes for NH4(+)-N and NO2(-)-N, respectively. The analysis also revealed that anammox/amoA and nxrA/(nirK+nirS) were the two key functional gene groups affecting processes associated with the NO3(-)-N transformation rate. The direct and indirect effect of functional gene groups further confirmed that nitrogen transformation processes are coupled at the molecular level, resulting in a mutual contribution to nitrogen removal in the TF.

Analysis of bacteria communities in an up-flow fixed-bed (UFB) bioreactor for treating sulfide in hydrocarbon wastewater

An up-flow fixed-bed (UFB) bioreactor with patented functional polyurethane foam (FPUF) carriers was used to treat sulfide in hydrocarbon wastewater. Community compositions of autotrophic and heterotrophic bacteria were analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). DGGE results showed that a relatively stable bacterial community composed of heterotrophic and autotrophic bacteria formed in the bioreactor by the end of experiment, which ensured 92-100% sulfide removal efficiencies. Furthermore, autotrophic genera of Thiobacillus and Thiomonas, as well as those of the heterotrophic genus of Acinetobacter survived and exhibited high sulfide oxidation activity under all three operational conditions. Different special genera were also observed under each operational condition, such as the halophilic genus of Nesterenkonia. In addition, a new genus of sulfide oxidation bacteria was found in the bioreactor, which had the ability to synthesize cytoplasm from organic compounds. These genera have wide applications for the treatment of sulfide in hydrocarbon wastewater.