Hongqiang Ren

Phosphorus fractions and matrix-bound phosphine in coastal surface sediments of the Southwest Yellow Sea

This paper characterizes the distribution of phosphorus fractions and matrix-bound phosphine (MBP) in coastal surface sediments of the Southwest Yellow Sea from 2006 to 2007. Total phosphorus (TP), inorganic phosphorus (IP) and organic phosphorus (OP) concentrations (mg kg(-1)) range from 278 +/- 3 to 768 +/- 15, 160 +/- 1 to 653 +/- 27, and 3.42+/- 0.05 to 267 +/- 22, respectively. MBP is a small portion of TP with values of 0.69 +/- 0.06 to 179 +/- 29 ng kg(-1). Phosphorus fractions and MBP are influenced strongly by riverine input and hydrodynamic conditions. High TP and MBP are found in the old Yellow River mouth and the Yangtze River mouth. OP and MBP are strongly negatively correlated to mean particle size. Significant positive correlations are found between MBP and IP and OM, suggesting that MBP production may be the microbially intermediated transformation of IP.

Physiological and biochemical responses of Microcystis aeruginosa to phosphite.

Phosphorus (P) is a key biological element and limiting nutrient in aquatic environments. Phosphate (+5) is traditionally associated with the P nutrient supply. However, phosphite (+3) has recently generated a great deal of interest, because of the possibility that it is a P source based on recognition of its vital role in the original life of the early earth. This study investigated whether phosphite can be an alternative P source for Microcystis aeruginosa PCC 7806, one of the predominant bloom species in freshwater systems. The results indicated that M. aeruginosa could not utilize phosphite as a sole P-nutrient directly for cell growth at any concentration, but that phosphite could boost cell numbers and chlorophyll a (Chl-a) content as long as phosphate was provided simultaneously. Specifically, Chl-a production increased sharply when 5.44 mg PL(-1) phosphite was added to 0.54 mg PL(-1) phosphate medium. Analysis of the maximum yield of PSII indicated that phosphite may stimulate the photosynthesis process of cells in phosphate-phosphite medium. In addition, phosphite failed to support cell growth, even though it more readily permeated the cells in P-deficient medium than in P-sufficient medium. Alkaline phosphatase activity (APA) analysis indicated that, unlike organic P, phosphite inhibits the response of cells to deficient P status, especially under P-deprived conditions.

Matrix-bound phosphine in paddy fields under a simulated increase in global atmospheric CO2

Environmental context. Although phosphine (PH3) is an important gaseous carrier in the phosphorus cycle, its production and environmental behaviour remain unclear. Paddy fields are thought to be one of the main sources responsible for the production and emission of PH3. Understanding the behaviour of PH3 in paddy fields under elevated CO2 concentration is crucial in understanding the phosphorus cycle and its response to rising global atmospheric CO2 concentration. Abstract. The behaviour of matrix-bound phosphine (MBP) in paddy fields under elevated [CO2] (ambient + 200 μmol mol–1) is investigated to understand the soil phosphorus cycle and its link to increasing global atmospheric [CO2]. MBP concentrations range from 17.0 ± 5.8 to 1035 ± 331 ng kg–1. Concentrations at the transplanting and harvest stages are significantly higher than during the growing stages. The MBP level (212 ± 61 ng kg–1) under elevated [CO2] is slightly higher than under ambient [CO2] (189 ± 44 ng kg–1). Root exudates and addition of inorganic phosphate fertiliser speed up the production of MBP, whereas fast paddy growth and increasing air temperature accelerate the emission of MBP into the atmosphere. Significant positive correlations are found between MBP and inorganic phosphorus and organic matter, indicating that MBP may be produced from the microbial reduction of inorganic phosphorus in paddy fields.

Effect of reflux ratio on COD and nitrogen removals from coke plant wastewaters

A laboratory-scale anaerobic-anoxic-aerobic-moving bed biofilm reactor (A1-A2-O-MBBR) system was undertaken to treat coke plant wastewaters from two different factories (wastewater A and B). Wastewater B had higher BOD5/COD ratio and COD/TN ratio than wastewater A. The effects of reflux ratios on COD, TN and NH3-N removals were studied. Results indicated that, with the reflux ratio increased from 2 to 5, COD removals of wastewater A and wastewater B increased from 57.4% to 72.6% and 78.2% to 88.6%, respectively. Meanwhile, TN removals were also increased accompanying reflux ratio rise, from 53.1% to 74.4% for wastewater A and 64.2% to 83.5% for wastewater B. At the same reflux ratio, compared with wastewater A, higher COD and TN removal efficiencies were observed in wastewater B, which had higher BOD5/COD and COD/TN ratio. Reflux ratio had no significant influence on NH3-N removal; 99.0% of the overall NH3-N removal efficiency was achieved by the system for both coke plant wastewaters at any tested reflux ratio. MBBR was effective in NH3-N removal, and about 95% of the NH3-N was removed in the MBBR.

Biofilm regeneration on carriers in MBBR used for vitamin C wastewater treatment.

Methods were investigated for biofilm regeneration on carriers in a moving bed biofilm reactor used for vitamin C production wastewater treatment. Three ordinary chemical cleaning agents (hydrochloric acid, sodium hydroxide, and sodium hypochlorite) and physical drying were chosen for evaluation as methods for biofilm detachment. The results showed that these methods all had some degree of biofilm removal effectiveness. Treatment with 3% hydrochloric acid (w/w) achieved the maximum degree of biofilm detachment, at 75.2%. Biofilm biomass re-formed on carriers, from the maximum degree of biofilm detachment, quickly by an increase of 76.17 g m(-2) month(-1). It was concluded that treatment with 3% acid was the best choice for biofilm removal and regeneration.

Comparison of extracellular polymeric substances (EPS) extraction from two different activated sludges

The characteristics of extracellular polymeric substances (EPS) extracted with five different extraction protocols from two different activated sludges were studied. The results showed that the major EPS constituent extracted by centrifugation was protein for the sludge in sequencing batch reactor treating chemical wastewater, and nucleic acid for the sludge in moving bed biofilm reactor treating synthetic urban wastewater. The order of EPS extraction amounting from the two sludges was formaldehyde + NaOH > formaldehyde + heating > EDTA > heating > centrifugation. The different extraction methods, the wastewater type, and activated sludge source greatly affected the amount and composition of EPS. The chemical extracted methods were more effective than the physical methods in extracting EPS for the two sludges. Moreover, formaldehyde combined NaOH was most effective in extracting EPS for the two sludges. However, chemical extraction could contaminate the EPS solution, which was pointed out by infra-red analysis and was also proved by cell lyses during EPS extraction and carrying over of the chemical extractant. Therefore, this study highlights that the choice of EPS extraction method should consider both the extraction yield and content and the contamination of extracting reagents to the EPS solution. The extraction procedures should be optimized and most effective.

Sources of matrix-bound phosphine in advanced wastewater treatment system

Phosphine (PH3), a highly toxic and reductive gas, has been explored in biogases[1,2] and it proves also to be ubiquitous even in remote atmospheric air at a concentration in the order of (pg--ng) /m3 [3]. For more than one hundred years, sources and mechanisms of biological phosphine formation in natural and engineered environments have been investigated and discussed[4].

Can fluorescence spectrometry be used as a surrogate for predicting the dissolved organic nitrogen and its bioavailable portion in wastewater effluents

This study investigated the applicability of fluorescence excitation-emission matrices coupled with parallel factor analysis (EEM-PARAFAC) for predicting dissolved organic nitrogen (DON) and bioavailable DON (ABDON) in wastewater effluents. A four component PARAFAC model was developed using 40 EEMs of effluent samples from four full-scale wastewater treatment plants. The DON showed a poor correlation with the PARAFAC components (-0.117xa0<xa0rxa0<xa00.308, pxa0=xa00.053-0.471), while ABDON correlated significantly with protein-like components C2 (rxa0=xa00.511, pxa0<xa00.05) and C3 (rxa0=xa00.576, pxa0<xa00.05, Pearson test). Further, a multivariate linear regression model having a good predictive capability for ABDON with mean absolute error of 12.0% was developed. Results demonstrate that the application of fluorescence spectroscopy for predicting effluent DON may have limitations, however, it could provide an alternative tool for predicting effluent ABDON.

Inorganic fractions in extracellular polymeric substance extracted from activated sludge and biofilm samples by different methods.

This study highlighted the inorganic fractions in the extracellular polymeric substance (EPS) extract from two activated sludges and one biofilm. Nine EPS extraction methods (centrifugation, sonication, cation exchange resin (CER) + sonication, CER, heating, formaldehyde + heating, formaldehyde + NaOH, ethanol and EDTA) were used in the study. The EPS extracts had large inorganic fractions, which ranged from 28% to 94% of the EPS dry weight. The EPS inorganic fraction was dependent on the source of the sludge and wastewater, the kinds of bacteria and the extraction method. The EPS extracts obtained by heating and sonication had smaller inorganic fractions than those obtained by centrifugation. The compositions of the inorganic fraction of EPS extracts obtained with CER and sonication + CER showed similar trends. The chemical extraction methods could contaminate the inorganic composition of EPS extracts by impurities, carrying over of the extractant itself or by changing the pH of the solution. Ethanol was the most effective extractant for obtaining inorganic ions.

Effect of Ce3+ on soluble microbial products production in anaerobic granular sludge digestion

Upflow anaerobic sludge bed reactors fed on glucose were used to investigate the effects of Ce(3+) on soluble microbial products (SMP) production, which is the majority of the residual chemical oxygen demand present in the effluent. It was found that Ce(3+) concentration of 0.05 mg/L had no significant effect on the amount of SMP production, whereas that of 1 mg/L led to the increase in SMP production. The molecular-weight distribution and carbohydrate analysis indicated that an increase in SMP production may be partly attributed to the release of extracellular polymeric substances (EPS) into the bulk solution resulted from cerium toxicity, and the nucleic acids analysis suggested that increased cell lysis also contributed to SMP accumulation in the presence of Ce(3+). The increase in SMP production in the presence of Ce(3+) is possibly a consequence of the release of EPS and increased cell lysis due to cerium toxicity.