Improvement of carbon usage for phosphorus recovery in EBPR-r and the shift in microbial community.

Enhanced biological phosphorus removal and recovery (EBPR-r) is a biofilm process that makes use of polyphosphate accumulating organisms (PAOs) to remove and recover phosphorus (P) from wastewater. The original process was inefficient, as indicated by the low P-release to carbon (C)-uptake (Prel/Cupt) molar ratio of the biofilm. This study successfully validated a strategy to improve the Prel/Cupt ratio by at least 3-fold. With an unchanged supply of carbon in the recovery stream, an increase in the hydraulic loading in stages I, II and III (7.2, 14.4 and 21.6 L, respectively) resulted in a 43% increase in the Prel/Cupt ratio (0.069, 0.076 and 0.103, respectively). The ratio further increased by 150% (from 0.103 to 0.255) when the duration of the P uptake period was increased from 4 h (stage III) to 10 h (stage IV). Canonical correspondence analysis showed that, correlated to the 3-fold increase in the Prel/Cupt ratio, there was an increase in the abundance of PAOs ("Candidatus Accumulibacter" Clade IIA) and a decrease in the occurrence of glycogen accumulating organisms (GAOs) (family Sinobacteraceae). However, the four stage operation impaired denitrification, resulting in a 5-fold reduction in the Nden/Pupt ratio. The decline in denitrification was consistent with a decrease in the abundance of denitrifiers including denitrifying PAOs (family Comamonadaceae and "Candidatus Accumulibacter" Clade IA). Overall, a strategy to facilitate more efficient use of carbon was validated, enabling a 3-fold carbon saving for P recovery. The new process enabled up to 80% of the wastewater P to be captured in a P-enriched stream (>90 mg/L) with a single uptake/release cycle of recovery.

Simultaneous phosphorus uptake and denitrification by EBPR-r biofilm under aerobic conditions: effect of dissolved oxygen.

A biofilm process, termed enhanced biological phosphorus removal and recovery (EBPR-r), was recently developed as a post-denitrification approach to facilitate phosphorus (P) recovery from wastewater. Although simultaneous P uptake and denitrification was achieved despite substantial intrusion of dissolved oxygen (DO >6 mg/L), to what extent DO affects the process was unclear. Hence, in this study a series of batch experiments was conducted to assess the activity of the biofilm under various DO concentrations. The biofilm was first allowed to store acetate (as internal storage) under anaerobic conditions, and was then subjected to various conditions for P uptake (DO: 0-8 mg/L; nitrate: 10 mg-N/L; phosphate: 8 mg-P/L). The results suggest that even at a saturating DO concentration (8 mg/L), the biofilm could take up P and denitrify efficiently (0.70 mmol e(-)/g total solids*h). However, such aerobic denitrification activity was reduced when the biofilm structure was physically disturbed, suggesting that this phenomenon was a consequence of the presence of oxygen gradient across the biofilm. We conclude that when a biofilm system is used, EBPR-r can be effectively operated as a post-denitrification process, even when oxygen intrusion occurs.

Inspiration from old dyes: tris(stilbene) compounds as potent gram-positive antibacterial agents.

Herein we describe the preparation and structure-activity relationship studies on range of stilbene based compounds and their antibacterial activity. Two related compounds, each bearing carboxylic acid moieties, exhibit good activity against several bacterial strains, including methicillin-resistant Staphylococcus aureus MRSA (ATCC 33592 and NCTC 10442). Compound 10 was most active against Moraxella catarrhalis with minimum inhibitory concentrations (MICs) of 0.12-0.25 µg mL(-1) and against Staphylococcus spp. with MICs ranging from 2-4 µg mL(-1). The derivative 17 showed increased activity with MICs of 0.06-0.25 µg mL(-1) against M. catarrhalis and 0.12-1 against Staphylococcus spp. This level of activity is similar to that reported for S. aureus for antibiotics, such as vancomycin, with MICs of ≤2.0 µg mL(-1) and clindamycin with MICs of ≤0.5 µg mL(-1). As an indicator of toxicity, 17 was tested for its ability to lyse sheep erythrocytes, and showed low haemolytic activity. Such results highlight the value of tris(stilbene) compounds as antibacterial agents providing suitable properties for further development.

A new method for ranking potential hazards and risks from wastes.

A quantitative approach for assessing hazards facilitates decision making on hazardous waste management practices. In this study, a scoring approach was developed to evaluate the physical, human health, environmental and amenity hazard aspects and risks (in case of exposure) of waste streams. The approach was based on the 15 hazard properties (HPs) defined in European Commission Waste Framework Directive 2008/98/EC and their related Globally Harmonised System of Classification and Labelling of Chemicals (GHS) hazard statement codes (H-codes). Additionally, amenity and other hazards including space requirement, odour, dust, vermin, visual impact, radioactivity and physical injury were considered. A score of 0-3 was assigned to each of the H-codes or amenity and other hazards. The scoring approach consisted of: 1) determining the waste composition; 2) searching H-codes based on waste composition and assigning H-codes to the associated HPs; 3) calculating the hazard score for each of the four hazard aspects; and 4) calculating the total score for each waste. Two methods were used to calculate the total hazard score for 29 hazardous wastes. The wastes were ranked over a hazard spectrum to indicate the potential degree of hazard. The new hazard scoring approach can be used for prioritising efforts in managing wastes.

Enrichment of anodophilic nitrogen fixing bacteria in a bioelectrochemical system.

We demonstrated the ability of a bio-anode to fix dinitrogen (N2), and confirmed that diazotrophs can be used to treat N-deficient wastewater in a bioelectrochemical system (BES). A two-compartment BES was fed with an N-deficient medium containing glucose for >200 days. The average glucose and COD removal at an anodic potential of +200 mV vs. Ag/AgCl was 100% and 76%, respectively. Glucose removal occurred via fermentation under open circuit (OC), with acetate as the key byproduct. Closing circuit remarkably reduced acetate accumulation, suggesting the biofilm could oxidise acetate under N-deficient conditions. Nitrogen fixation required an anode and glucose; removing either reduced N2 fixation significantly. This suggests that diazotroph utilised glucose directly at the anode or indirectly through syntrophic interaction of an N2-fixing fermenter and an anodophile. The enriched biofilm was dominated (68%) by the genus Clostridium, members of which are known to be electrochemically active and capable of fixing N2.

A novel post denitrification configuration for phosphorus recovery using polyphosphate accumulating organisms.

Enhanced biological phosphorus removal (EBPR) has been widely used to remove phosphorus (P) from wastewater. In this study we report a novel modification to the EBPR approach, namely enhanced biological phosphorus removal and recovery (EBPR-r) that facilitates biological recovery of P from wastewater using a post denitrification configuration. The novel approach consists of two major steps. In the first step, a biofilm of phosphorus accumulating organisms (PAOs) is exposed to a wastewater stream in the absence of active aeration, during which P is taken up by the biofilm using nitrate and residual dissolved oxygen as electron acceptors. Thus, P and nitrogen (N) removal from wastewater is achieved. During the second step, the P enriched biofilm is exposed to a smaller recovery stream supplemented with an external carbon source to facilitate P release under anaerobic conditions. This allows P to be recovered as a concentrated liquid. The EBPR-r process was able to generate a P recovery stream four time more concentrated (28 mg-P/L) than the wastewater stream (7 mg-P/L), while removing nitrate (denitrification) from the wastewater stream. Repeated exposure of the biofilm (10 P-uptake and release cycles) to a recovery stream yielded up to 100 mg-P/L. Overall, EBPR-r is the first post denitrification strategy that can also facilitate P recovery during secondary wastewater treatment.