The acute effects of erythromycin and oxytetracycline on enhanced biological phosphorus removal system: shift in bacterial community structure.

Since extensive application, an increasing amount of antibiotics has been released into wastewater treatment plants. In this study, the enhanced biological phosphorus removal (EBPR) system was fed with synthetic wastewater containing erythromycin (ERY) and oxytetracycline (OTC) for 7 days to evaluate the variations of solution ortho-P (SOP), volatile fatty acid (VFA), poly-bhydroxyalkanoates (PHAs), specific oxygen uptake rater (SOUR), and microbial community in the EBPR system. The obtained results showed that the P-removal efficiency decreased to 0.0%, and at the end of the experiment, only less than 20% of the VFA could be consumed. Besides, the variable processes of P and PHAs were destroyed. Moreover, to better grasp the inhibitory mechanism of antibiotics, microbial community compositions of activated sludge sampled in all reactors were investigated by high-throughput sequencing techniques. Results of comparative and evolutionary analysis revealed that high concentrations (5 and 10 mg/L) of ERY and OTC could seriously shift microbial communities, while combined antibiotics could induce more. Additionally, Accumulibacter and Competibacter were two primary microorganisms at the genus level in the EBPR system. Accumulibacter decreased seriously for exposure to antibiotics, while Competibacter increased in all experimental reactors especially in combined antibiotics reactor.

Understanding the performance of microbial community induced by ZnO nanoparticles in enhanced biological phosphorus removal system and its recoverability.

In this study, the impacts of ZnO Nanoparticles (NPs) on the microbial community in enhanced biological phosphorus removal (EBPR) system and its recoverability were investigated. High-throughput sequencing was applied to study the microbial community shift. Results show that the species richness in the EBPR system was reduced under the condition of ZnO NPs with high concentration (above 6mg/L). Evolution analysis suggests that higher concentration ZnO NPs induced more microbial community shift. According to the analysis on genus level, Competibacter was more impressionable than Accumulibacter after exposure to 2mg/L ZnO NPs. Nonetheless, this phenomenon could not be found as the concentration of ZnO NPs got higher (above 6mg/L). Accumulibacter could reach to the initial level after recover for 20days, whereas Competibacter could not recover even when the concentration of ZnO NPs was only 2mg/L. Interestingly, although the phosphorus removal (P-removal) process was re-achieved, the microbial community in reactors was irreversible.

Short-term performance of enhanced biological phosphorus removal (EBPR) system exposed to erythromycin (ERY) and oxytetracycline (OTC).

The effects of Erythromycin (ERY) and oxytetracycline (OTC), including individual and combinative effect, on enhanced biological phosphorus removal (EBPR) system within a short-term (24h) were evaluated in this study. Results showed that the P-removal efficiency decreased to 34.6% and 0.0% under the effect of ERY (10mg/L) and OTC (10mg/L) for 24h. OTC concentration higher than 5mg/L was sufficient to cause serious adverse impact on the EBPR performance. While the performance of EBPR system will be impacted by ERY above 10mg/L. OTC, due to its special antibacterial action to the gram-negative bacteria which most PAOs belong to, has more serious negative effect on the EBPR performance than ERY does. Moreover, in the combined antibiotics test, neither synergistic nor antagonistic effect was detected between ERY and OTC. Finally, ERY (10mg/L) and OTC (10mg/L) could inhibit the microorganisms' activity, while couldn't induce serious microorganisms death within 24h.

Long-term effect of low concentration Cr(VI) on P removal in granule-based enhanced biological phosphorus removal (EBPR) system.

In light of the fact that most wastewater in China contained both industrial and domestic wastewater, a 52-d systematical investigation was conducted on the long-term effect of low concentration Cr(VI) (0.3-0.8 mg L(-1)) on P removal performance of granule-based EBPR system in this study. The mechanisms were likewise discussed. Results showed that high Cr(VI) concentration (⩾0.5 mg L(-1)) could significantly inhibit P removal, while this phenomenon was not found when Cr(VI) concentration was less than (or equal to) 0.4 mg L(-1). Most of the granules was disintegrated and filamentous bacteria overgrew inducing sludge bulking occurred at 0.7 mg L(-1) Cr(VI). During the exposure test, the abundance of poly-phosphate-accumulating organisms (PAOs) significantly decreased while the populations of glycogen accumulating organisms (GAOs) and other bacteria increased. Both production and degradation of poly-ß-hydroxyakanoates (PHAs) were apparently inhibited. An improved polysaccharide/protein (PS/PN) ratio was observed with the increasing Cr(VI) concentration, implying excessive polysaccharide was secreted by microorganisms to support its resistance to the toxicity of Cr(VI). Besides, good linear regression between PS/PN ratio and the granule size (R(2)=-0.86, p<0.01) was obtained, indicating that high PS/PN was adverse to granule stability. Correlation analysis indicated that the accumulation of granules intracellular Cr was directly responsible for the observed inhibitory effect on P removal process. The long-term Cr(VI) treatment had irreversible effects on granule-based EBPR system as it could not revive after a 16-d recovery process.

The effect of COD loading on the granule-based enhanced biological phosphorus removal system and the recoverability.

In this study, the effect of varied COD loading (200, 400, 500, 600 and 800 mg L(-1)) on stability and recoverability of granule-based enhanced biological phosphorus removal (EBPR) system was investigated during continuously 53-d operation. Results showed that COD loading higher than 500 mg L(-1) could obviously deteriorate the granular EBPR system and result in sludge bulking with filamentous bacteria. High COD loading also changed the transformation patterns of poly-ß-hydroxyalkanoates (PHAs) and glycogen in metabolism process of polyphosphate-accumulating organisms (PAOs) and inhibited the EPS secretion, which completely destroyed the stability and integrality of granules. Results of FISH indicated that glycogen-accumulating organisms (GAOs) and other microorganisms had a competitive advantage over PAOs with higher COD loading. The community composition and EBPR performance were recovered irreversibly in long time operation when COD loading was higher than 500 mg L(-1).

Impact of Cr(VI) on P removal performance in enhanced biological phosphorus removal (EBPR) system based on the anaerobic and aerobic metabolism.

Influence of Cr(VI) on P removal in enhanced biological phosphorus removal (EBPR) system was investigated with respect to the composition of poly-phosphate-accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs), the transformation of poly-ß-hydroxyalkanoates (PHA) and glycogen, enzymes' activities, and the intracellular Cr. Whether EBPR system could revive after Cr(VI) shock was also explored. Results showed P removal performance was completely inhibited by Cr(VI) with the concentration more than 5 mg L(-1). PAOs were more sensitive to Cr(VI) than GAOs and the other bacteria were. PHA consumption, glycogen synthesis and adenylate kinase's activity had been inhibited by 5 mg L(-1) Cr(VI). Both adenylate kinase's activity and P removal efficiency were negatively correlated with the intracellular Cr. Recovery experiments revealed that P removal performance with 5 mg L(-1) Cr(VI) shock could revive after a 2-day recovery treatment, while systems with high level Cr(VI) (20 and 60 mg L(-1)) shock could not.

Identification of anthropogenic influences on water quality of rivers in Taihu watershed.

Surface water bodies are progressively subjected to stress as a result of anthropogenic activities. This study assessed and examined the impact of human activities on spatial variation in the water quality of 19 rivers in the Taihu watershed. Concentrations of physicochemical parameters of surface water quality were determined at the mouth of each river during the period of 2000-2004. Multivariate statistical techniques were applied to identify characteristics of the water quality in the studied rivers. The results showed that rivers strongly influenced by household wastewater have the highest concentrations of nutrients (TN and TP). Moreover, rivers in the vicinity of a metropolis presented low dissolved oxygen (DO) levels. However, organic-chemical pollution (petroleum and volatile phenolics) was identified with high localization. Two rivers influenced by sewage from industry and ships were distinguished from other rivers with high values of petroleum. The Taige channel, a river located in Changzhou City that is strongly influenced by wastewater from industry, was characterized with an extraordinarily high value of volatile phenolics. Rivers passing through countries, especially through hilly countries were characterized with high DO contents and low nutrient and organic-chemical pollution, suggesting that agriculture puts less pressure on water quality in adjacent rivers. Therefore, more effort should be made in controlling point pollution to restore water quality in rivers adjacent to cities.