Expanding DEMON Sidestream Deammonification Technology Towards Mainstream Application.

A cross-Atlantic R&D-cooperation involving three large utilities investigated the feasibility of mainstream deammonification-the application of partial nitritation/anammox for full-plant treatment of municipal wastewater at ambient temperatures. Two major process components have been implemented, 1) bioaugmentation of aerobic- and anaerobic ammonia oxidizers (AOB and AMX) from the DEMON-sidestream sludge liquor treatment to the mainstream and 2) implementation of hydrocyclones to select for anammox granules and retain them in the system. Different operation modes have been tested at laboratory- and pilot-scale in order to promote the short-cut (more direct anammox route) in nitrogen removal metabolism. At the full-scale installation at Strass WWTP, stable repression of nitrite oxidizing biomass (NOB) has been achieved for several months. Significant anammox enrichment in the mainstream has been monitored while high efficiency in the sidestream-process has been maintained (96% annual average ammonia removal).

Going for mainstream deammonification from bench to full scale for maximized resource efficiency.

A three-pronged coordinated research effort was undertaken by cooperating utilities at three different experimental scales investigating bioaugmentation, enrichment and performance of anammox organisms in mainstream treatment. Two major technological components were applied: density-based sludge wasting by a selective cyclone to retain anammox granules and intermittent aeration to repress nitrite oxidizers. This paper evaluates process conditions and operation modes to direct more nitrogen to the resource-saving metabolic route of deammonification.

The effect of maize silage as co-substrate for swine manure on the bacterial community structure in biogas plants.

The qualitative and quantitative changes in the bacterial community composition in two mesophilic, commercially used biogas plants were monitored by denaturing gradient gel electrophoresis (DGGE) and real-time PCR. The main objective was to evaluate the influence of the co-substrate maize silage on total bacteria and some selected bacterial groups by comparing full-scale reactors fed solely with pig manure or additionally with maize silage. DGGE fingerprints reflected shifts in the bacterial community structure associated with maize silage as co-substrate and the real-time PCR results showed clear changes in the quantitative composition of the bacterial consortia of each fermenter. A clear dominance of Clostridia in all surveyed fermenters and considerably lower abundance of Bacteroidetes in the biogas plant fed with maize silage was shown.

Quantitative and qualitative effects of bioaugmentation on ammonia oxidisers at a two-step WWTP.

Large waste water treatment plants (WWTP) often operate nitrification in two different process environments: the cold-dilute sewage is treated in the mainstream nitrification/denitrification system, while the high strength ammonia liquors from sludge dewatering are treated in a separate high temperature reactor (SBR). This study investigates transfer from nitrifier biomass into a two-stage WWTP, commonly referred to as bioaugmentation. Besides the quantitation of ammonia oxidising bacteria (AOB), community differences were analysed with two techniques, denaturing gradient gel electrophoresis and real-time PCR melt curve analysis. It was shown that, without bioaugmentation, two distinct AOB communities establish in the mainstream and in the SBR, respectively. A gradual shift of the two AOB communities with increasing pump rates between the systems could be demonstrated. These molecular findings support process engineering experience, that cycling of waste activated sludge improves the ability of AOB to adapt to different process environments.

Application of denaturing gradient gel electrophoresis for analysing the gut microflora of Lumbricus rubellus Hoffmeister under different feeding conditions.

The earthworm, Lumbricus rubellus, plays an essential role in soil ecosystems as it affects organic matter decomposition and nutrient cycling. By ingesting a mixture of organic and mineral material, a variety of bacteria and fungi are carried to the intestinal tract of the earthworm. To get a better understanding of the interactions between L. rubellus and the microorganisms ingested, this study tried to reveal if the diet affects the composition of the gut microflora of L. rubellus or if its intestinal tract hosts an indigenous, species-specific microbiota. A feeding experiment with L. rubellus was set up; individuals were collected in the field, transferred to a climate chamber and fed with food sources of different quality (dwarf shrub litter, grass litter or horse dung) for six weeks. DNA was extracted from the guts of the earthworms, as well as from the food sources and the surrounding soil, and further analysed by a molecular fingerprinting method, PCR-DGGE (Polymerase Chain Reaction -- Denaturing Gradient Gel Electrophoresis). We were able to demonstrate that the gut microbiota was strongly influenced by the food source ingested and was considerably different to that of the surrounding soil. Sequencing of dominant bands of the bacterial DGGE fingerprints revealed a strong occurrence of y-Proteobacteria in all gut samples, independent of the food source. A specific microflora in the intestinal tract of L. rubellus, robust against diet changes, could not be found.