Analysis of the microbial community structure and function of a laboratory scale enhanced biological phosphorus removal reactor

A laboratory scale sequencing batch reactor (SBR) operating for enhanced biological phosphorus removal (EBPR) and fed with a mixture of volatile fatty acids (VFAs) showed stable and efficient EBPR capacity over a four-year-period. Phosphorus (P), poly-beta-hydroxyalkanoate (PHA) and glycogen cycling consistent with classical anaerobic/aerobic EBPR were demonstrated with the order of anaerobic VFA uptake being propionate, acetate then butyrate. The SBR was operated without pH control and 63.67+/-13.86 mg P l(-1) was released anaerobically. The P% of the sludge fluctuated between 6% and 10% over the operating period (average of 8.04+/-1.31%). Four main morphological types of floc-forming bacteria were observed in the sludge during one year of in-tensive microscopic observation. Two of them were mainly responsible for anaerobic/aerobic P and PHA transformations. Fluorescence in situ hybridization (FISH) and post-FISH chemical staining for intracellular polyphosphate and PHA were used to determine that 'Candidatus Accumulibacter phosphatis' was the most abundant polyphosphate accumulating organism (PAO), forming large clusters of coccobacilli (1.0-1.5 mum) and comprising 53% of the sludge bacteria. Also by these methods, large coccobacillus-shaped gammaproteobacteria (2.5-3.5 mum) from a recently described novel cluster were glycogen-accumulating organisms (GAOs) comprising 13% of the bacteria. Tetrad-forming organisms (TFOs) consistent with the 'G bacterium' morphotype were alphaproteobacteria , but not Amaricoccus spp., and comprised 25% of all bacteria. According to chemical staining, TFOs were occasionally able to store PHA anaerobically and utilize it aerobically.

Optimising cleaning behaviour: minimising the costs and maximising ectoparasite removal

Little is known of how client fish minimise the costs of cleaning behaviour while maximising ectoparasite removal by cleaner fish. Previous studies have found that abundance on fish and infestation behaviour of gnathiid isopods, the main parasite eaten by cleaner fish, varies diurnally. We examined whether reduced foraging is a cost of cleaning behaviour in clients and whether the behaviour of the client fish, the thick-lipped wrasse Hemigymnus melapterus, towards the cleaner fish Labroides dimidiatus varied diurnally to maximise ectoparasite removal, possibly in response to the diurnal changes in the abundance and infestation patterns of gnathiids. We found that during the midday and afternoon, client foraging rates were negatively related to the duration and frequency of inspections, suggesting that cleaning may, at some times of the day, be energetically costly to the client in terms of reduced foraging opportunities. Surprisingly, we found that the duration and frequency of inspections of clients by cleaners did not vary among diel time periods. A model of gnathiid dynamics on individual fish is proposed. It shows that the observed diurnal pattern in gnathiid abundance on fish can be generated with the constant duration and frequency of inspections that was observed in this study. Thus clients would not have more gnathiids removed by modifying their cleaning behaviour.

Benchmarking nitrogen removal suspended-carrier biofilm systems using dynamic simulation

We are witnessing an enormous growth in biological nitrogen removal from wastewater. It presents specific challenges beyond traditional COD (carbon) removal. A possibility for optimised process design is the use of biomass-supporting media. In this paper, attached growth processes (AGP) are evaluated using dynamic simulations. The advantages of these systems that were qualitatively described elsewhere, are validated quantitatively based on a simulation benchmark for activated sludge treatment systems. This simulation benchmark is extended with a biofilm model that allows for fast and accurate simulation of the conversion of different substrates in a biofilm. The economic feasibility of this system is evaluated using the data generated with the benchmark simulations. Capital savings due to volume reduction and reduced sludge production are weighed out against increased aeration costs. In this evaluation, effluent quality is integrated as well.

Review of "Clearing the Smoke: Assessing the Science Base for Tobacco Harm Reduction"

Review of Clearing the Smoke: Assessing the Science Base for Tobacco Harm Reductionbby K. STRATTON, P. SHEATHE, R. WALLACE & S. BANDURANT Washington DC, National Academy Press, 2001, xix + 636 pp, US$49.95, ISBN 0309 07282 4 (hbk)

Improved nitrogen removal by application of new nitrogen-cycle bacteria

In order to meet increasingly stringent European discharge standards, new applications and control strategies for the sustainable removal of ammonia from wastewater have to beimplemented. In this paper we discuss anitrogen removal system based on the processesof partial nitrification and anoxic ammoniaoxidation (anammox). The anammox process offers great opportunities to remove ammonia in fully autotrophic systems with biomass retention. No organic carbon is needed in such nitrogenremoval system, since ammonia is used a selectron donor for nitrite reduction. The nitrite can be produced from ammonia in oxygen-limited biofilm systems or in continuous processes without biomass retention. For successful implementation of the combined processes, accurate biosensors for measuring ammonia and nitrite concentrations, insight inthe complex microbial communities involved, and new control strategies have to be developed and evaluated.

Full-scale demonstration of biological nutrient removal in a single tank SBR process

Complete biological nutrient removal (BNR) in a single tank, sequencing batch reactor (SBR) process, is demonstrated here at full-scale on a typical domestic wastewater. The unique feature of the UniFed process is the introduction of the influent into the settled sludge blanket during the settling and decant periods of the SBR operation. This achieves suitable conditions for denitrification and anaerobic phosphate release which is critical to successful biological phosphorus removal, It also achieves a selector effect, which helps in generating a compact, well settling biomass in the reactor. The results of this demonstration show that it is possible to achieve well over 90% removal of GOD, nitrogen and phosphorus in such a process. Effluent quality achieved over a six-month operating period directly after commissioning was: 29 mg/l GOD, 0.5 mg/l NH4-N, 1.5 mg/l NOx-N and 1.5 mg/l PO4-P (50%-iles of daily samples). During an 8-day, intensive sampling period, the effluent BOD5 was

Simultaneous nitrification, denitrification, and phosphorus removal in a lab-scale sequencing batch reactor

Simultaneous nitrification and denitrification (SND) via the nitrite pathway and anaerobic-anoxic-enhanced biological phosphorus removal (EBPR) are two processes that can significantly reduce the energy and COD demand for nitrogen and phosphorus removal. The combination of these two processes has the potential of achieving simultaneous nitrogen and phosphorus removal with a minimal requirement for COD. A lab-scale sequencing batch reactor (SBR) was operated in alternating anaerobic-aerobic mode with a low dissolved oxygen (DO) concentration (0.5 mg/L) during the aerobic period, and was demonstrated to accomplish nitrification, denitrification, and phosphorus removal. Under anaerobic conditions, COD was taken up and converted to poly-hydroxyalkanoates (PHAs), accompanied by phosphorus release. In the subsequent aerobic stage, PHA was oxidized and phosphorus was taken up to

Seed viability and dormancy mechanisms of Leucopogon melaleucoides Cunn. ex DC. (Epacridaceae)

Leucopogon melaleucoides, a flowering shrub, is desired by floricultural markets but is difficult to propagate. Seed viability was tested and dormancy mechanisms were studied to develop a commercial propagation system. Although around 56% of seed were viable, germination was completely inhibited unless the endocarp was removed. After-ripened seed (8 months after collection) germinated faster than fresh seed (2 days after collection), but germination occurred over a prolonged period (155 days). Germination of after-ripened seed was promoted with GA(3) or a commercial smoke product containing unknown plant growth regulators. All viable seed treated with GA(3) at 1000 mg L-1 had germinated after 24 days. The results suggest that both a physical and physiological dormancy mechanism occur for this species, with removal of the endocarp and pretreatment with 1000 mg L-1 GA(3) promoting complete germination of viable seed.

Fruit processing, seed viability and dormancy mechanisms of Persoonia sericea A. Cunn. ex R. Br. and P-virgata R. Br. (Proteaceae)

The morphology of the fruit and difficulties with fruit processing impose major limitations to germination of Persoonia sericea and P. virgata. The mesocarp must be removed without harming the embryo. Fermentation of fruit or manual removal of the mesocarp was effective but digestion in 32% hydrochloric acid (HCl) completely inhibited germination. The endocarp is extremely hard and therefore very difficult and time consuming to remove without damaging the seeds. The most efficient method was cracking the endocarp with pliers, followed by manual removal of seeds. Germination was completely inhibited unless at least half of the endocarp was removed. Microbial contamination of the fruit and seeds was controlled by disinfestation and germination of the seed under aseptic conditions. The results suggest that dormancy in these species is primarily due to physical restriction of the embryo by the hard endocarp.

Quantifying potential nitrogen removal by denitrification in stream sediments at a regional scale

Potential denitrification rates were measured using the acetylene block method, in sediments collected from streams in the sub-tropical, south-east Queensland region of Australia. Our aim was to estimate how much nitrogen could be removed from lotic systems by denitrification at the regional scale. Denitrification measured at 65 sites in August and September from a catchment of 22700 km(2) was extrapolated to all streams and rivers in the region based on the sediment area available for denitrification. Denitrification rates ranged between 4 and 950 mumol N m(-2) h(-1), with most sites having rates below 150 mumol N m(-2) h(-1). Based on these results, the current study estimates that a total of 305 t of nitrogen could be denitrified per year from all streams and rivers in the region, representing 6% of the total annual nitrogen load from surrounding land use. During baseflow conditions, when nitrogen loads to streams are low, the proportion of nitrogen removed through denitrification would be substantially higher, in some cases removing 100% of the nitrogen load. It is proposed that denitrification is an important process maintaining low concentrations of dissolved inorganic nitrogen under baseflow conditions and is therefore likely to enhance nitrogen limitation of primary production in this region.