Biomedical subjects

P Arnz

Publications and source records attributed to P Arnz.

4 recordsLinked to original sources

PubMed2002

Simultaneous P and N removal in a sequencing batch biofilm reactor: insights from reactor- and microscale investigations.

A sequencing batch biofilm reactor (SBBR) with well established enhanced biological phosphate removal (EBPR) was subjected to higher ammonium concentrations to stimulate and eventually implement simultaneous nitrification. Changes of activity and populations were investigated by a combination of online monitoring, microsensor measurements and fluorescence in situ hybridisation (FISH) of biofilm sections. Nitrification and nitrifying bacteria were always restricted to the periodically oxic biofilm surface. Both, activity and population size increased significantly with higher ammonium concentrations. Nitrification always showed a delay after the onset of aeration, most likely due to competition for oxygen by coexisting P accumulating and other heterotrophic bacteria during the initial aeration phase. This view is also supported by comparing oxygen penetration and oxygen uptake rates under low and high ammonium conditions. Therefore, simultaneous nitrification and phosphorus removal in a P removing SBBR appears to be only possible with a sufficiently long oxic period to ensure oxygen availability for nitrifiers.

Bacteria↗

PubMed2001

Possible complication regarding phosphorus removal with a continuous flow biofilm system: diffusion limitation.

Diffusion limitation of phosphate possibly constitutes a serious problem regarding the use of a biofilm reactor for enhanced biological phosphorus removal. A lab-scale reactor for simultaneous removal of phosphorus and nitrate was operated in a continuous alternating mode of operation. For a steady-state operation with excess amounts of carbon source (acetate) during the anaerobic phase, the same amount of phosphate was released during the anaerobic phase as was taken up during the anoxic phase. The measured phosphorus content of the biomass that detached during backwash after an anoxic phase was low, 2.4 +/- 0.4% (equal to 24 +/- 4 mg P/g TS). A simplified computer model indicated the reason to be phosphate diffusion limitation and the model revealed a delicate balance between the obtainable phosphorus contents of the biomass and operating parameters, such as backwash interval, biofilm thickness after backwash, and phase lengths. The aspect of diffusion is considered of crucial importance when evaluating the performance of a biofilter for phosphate removal.

Anaerobiosis↗

PubMed2001

Interception of small particles by flocculent structures, sessile ciliates, and the basic layer of a wastewater biofilm.

We investigated attachment processes of hydrophobic and hydrophilic particles (diameter = 1 microm) to mature biofilms grown on clay marbles in a sequencing batch biofilm reactor. During a treatment cycle with filtered wastewater containing different fluorescent beads, the progression of particle density in various biofilm compartments (carrier biofilm, basic biofilm layer, biofilm flocs, and sessile ciliates) was determined by flow cytometry, confocal laser scanning microscopy and automated image analysis. Particles were almost completely removed from wastewater by typical processes of particle retention: up to 58% of particles attached to clay marbles, up to 15% were associated with suspended flocs, and up to 10% were ingested by sessile ciliates. Ingestion of particles by ciliates was exceptionally high immediately after wastewater addition (1,200 particles grazer(-1) x h(-1)) and continued until approximately 14% of the water had been cleared by ciliate filter feeding. Most probably, ciliate bioturbation increases particle sorption to the basic biofilm. Backwashing of the reactor detached pieces of biofilm and thus released approximately 50% of the particles into rinsing water. Clay marbles in the upper part of the reactor were more efficiently abraded than in the lower part. No indications for selective attachment of the applied hydrophobic and hydrophilic beads were found. As a consequence of interception patterns, organisms at elevated biofilm structures are probably major profiteers of wastewater particles; among them, ciliates may be of major importance because of their highly active digestive food vacuoles.

Animals↗

PubMed2001

Enhanced biological phosphorus removal in a semi full-scale SBBR.

A 17 m3 Sequencing Batch Biofilm Reactor (SBBR) was operated for enhanced biological phosphorus removal and nitrification for a period of 384 days. Enhanced biological phosphorus removal (EBPR) activity was instantly induced after start-up of EBPR operation mode and low phosphate effluent values were reached from the first batch onward. Process stability with regard to nitrification and EBPR were very good although high nitrate loads from backwashing disturbed the P removal performance. Due to anoxic conditions in the beginning of the cycle, readily degradable COD was depleted by denitrification. Consequently, particulate matter was the main carbon source for phosphorus accumulating organisms. Anaerobic hydrolysis or fermentation was found to be the rate limiting process in the SBBR cycle. Simultaneous denitrification occurred in the first 30 minutes of aeration and--to a lesser extent--during the remaining aeration time, enhancing nitrogen removal and indirectly also phosphorus removal.

Aerobiosis↗