Thomas Welander

Ideonella dechloratans gen.nov., sp.nov., a New Bacterium Capable of Growing Anaerobically with Chlorate as an Electron Acceptor

Summary The name Ideonella dechloratans is proposed for a new species of Gram-negative, polarly flagellated, chemoorganotrophic, rod shaped bacterium capable of growing anaerobically with chlorate as an electron acceptor. The bacterium is mesophilic, strictly respiratory and has a guanine plus cytosine-content in DNA of 68.1 mol%. Sequence data from 16S ribosomal RNA gene of the type strain, CCUG 30898 T , show Ideonella dechloratans to cluster phylogenetically within the beta subgroup of Proteobacteria . The bacterium was enriched and isolated from activated sludge from a municipal wastewater treatment plant.

Nitrification of landfill leachate using suspended-carrier biofilm technology

The possibility of nitrifying municipal landfill leachate using suspended-carrier biofilm technology was studied in three laboratory-scale reactors filled with three different types of carrier media. The effects of the temperature and the hydraulic retention time (HRT) on the volumetric nitrification rate were investigated. Steady-state nitrification rates were obtained in the processes after approximately 1 month of operation. The nitrification rate showed a rather weak dependence on the temperature, the rate at 5°C being approximately 77% of the rate at 20°C. The HRT had a more pronounced effect on the rate of nitrification, showing a considerable increase in nitrification rate with a decreased HRT. The highest efficiency was achieved for a carrier media consisting of small cubes of macroporous cellulose. A maximum nitrification rate of 40 g (NH+4-N)/(m3 reactor h) was obtained by use of this carrier at 20°C, an HRT of 14 h and a carrier filling degree of 10% of the reactor volume.

Reducing sludge production in aerobic wastewater treatment through manipulation of the ecosystem

Abstract The possibility of minimizing sludge production in aerobic wastewater treatment through manipulation of the ecosystem so that most of the bacterial biomass produced is consumed by predating protozoa and metazoa was studied. The study was carried out on different pulp and paper industry wastewaters. In all of the experiments, the wastewater was first subjected to treatment in a completely mixed, aerobic reactor without biomass retention, favouring the growth of fast-growing dispersed bacteria consuming the readily biodegradable organic matter in the wastewater. After treatment at this stage, the wastewater was led to a reactor for growth of predators consuming the bacteria. Different designs of the predator stage, i.e. biofilm and suspended growth reactors, were used in different experiments. In all of the experiments, the total suspended solids (TSS) content of the wastewater increased considerably in the first reactor because of the production of bacterial biomass after which it was reduced significantly in the second reactor in which large amounts of different types of protozoa and metazoa developed. The apparent sludge yield in the processes varied between 0.01 and 0.23 kg TSS/kg COD removed, which is considerably lower than the yields generally obtained for treatment of similar wastewaters in conventional treatment processes.

The effect of different carbon sources on respiratory denitrification in biological wastewater treatment

Abstract The respiratory denitrification activity of activated sludge bacteria with different carbon sources (acetic acid, crude syrup, hydrolyzed starch, methanol—with and without a small amount of yeast extract) was studied in long-term continuous cultivations and batch tests. Mass balance calculations showed that the main product in long-term cultivations with all carbon sources was molecular nitrogen. However, the type of carbon source had a significant influence on the denitrification rate, denitrification yield, sludge yield and the composition of the microflora. With acetate and methanol higher denitrification yields, lower sludge yields and more true (end product N 2 ) denitrifying bacteria were obtained than with crude syrup and hydrolyzed starch. Furthermore, with acetate a higher growth rate and a higher denitrification rate was obtained than with methanol.

USE OF PROTOZOA AND METAZOA FOR DECREASING SLUDGE PRODUCTION IN AEROBIC WASTEWATER TREATMENT

SummaryA new approach to decreasing sludge production in aerobic biological wastewater treatment involving use of protozoa and metazoa was tested. The dissolved organics in the two synthetic wastewaters (based on acetic acid and methanol, respectively) tested were decomposed to >90% and the biomass production was decreased by 60–80%. The total sludge yield, expressed as total suspended solids per gram chemical oxygen demand removed, was 0.17 g TSS/g COD in the system fed acetic acid, whereas it was 0.05 g TSS/g COD in the system fed methanol. The explanation for this difference was that in the system fed methanol, dispersed bacteria were obtained that were easily grazed by the protozoa and metazoa in the predator stage. In the system fed acetic acid, the bacteria formed zoogloeal flocs, which protected them from grazing in the predator stage. With both carbon sources a significant release of nitrate (> 7 mg N/l) and of phosphate (> 2.5 mg P/l) was observed in the effluent.

Production of polyhydroxyalkanoates by glycogen accumulating organisms treating a paper mill wastewater

A process for production of polyhydroxyalkanoates (PHA) by activated sludge treating a paper mill wastewater was investigated. The applied strategy was to select for glycogen accumulating organisms (GAOs) by alternating anaerobic/aerobic conditions. Acidogenic fermentation was used as pretreatment to convert various organic compounds to volatile fatty acids which are preferable substrates for PHA production. Enrichment resulted in a culture dominated by GAOs related to Defluviicoccus vanus (56%) and Candidatus Competibacter phosphatis (22%). Optimization of PHA accumulation by the enriched GAO culture was performed through batch experiments. Accumulation of PHA under anaerobic conditions was limited by the intracellular glycogen stored. Under aerobic conditions significant glycogen production (to 25% of sludge dry weight) was observed alongside PHA accumulation (to 22% of sludge dry weight). By applying a subsequent anaerobic period after an initial aerobic, the produced glycogen could be utilized for further PHA accumulation and by this strategy PHA content was increased to 42% of sludge dry weight. The PHA yield over the entire process was 0.10 kg per kg of influent COD treated which is similar to what has been achieved with a process applying feast/famine enrichment strategy with the same wastewater.

Anoxic biological phosphorus removal in a full-scale UCT process

Abstract Enhanced biological phosphorus removal is based on the selective enrichment of bacteria accumulating inorganic polyphosphate, obtained at a cyclic regime of alternating anaerobic and aerobic conditions. In the University of Cape Town (UCT) process for combined nitrogen and phosphorus removal, polyphosphate-accumulating bacteria will also be exposed to nitrate in the anoxic zone, i.e. an electron acceptor that may be utilized as well as the oxygen of the aerobic zone. During a 1-year study of the full-scale UCT process run at Oresundsverket, Helsingborg, special attempts were made to quantify the relative contribution of an anoxic phosphate uptake at full-scale conditions: the dominant chemical oxygen demand (COD) uptake in the anaerobic zone could be identified as poly-β-hydroxy-alkanoates (PHA). PHA accumulation was at its largest during a test period with acetate added as an extra carbon source. At least one-third of the COD consumed in the anoxic zone could be identified as PHA. The anoxic sludge contained increased amounts of polyphosphate and reduced amounts of free orthophosphate compared to the anaerobic zone, approaching the levels of aerobic sludge. The metal bound orthophosphate remained largely unaffected, at a level of 25–30% of the total phosphorus content. After correction for the sludge recycling of the system, the formation of inorganic polyphosphate in the anoxic zone itself was estimated to be 30% of the total. When the metabolic activity was tested under controlled conditions in batch, the anaerobic sludge of the plant showed a high denitrifying activity accompanied by a phosphorus uptake and a simultaneous consumption of intracellular PHA corresponding to 2 g-COD/g-N, i.e. half the theoretical value needed for denitrification when biomass growth is included. It is concluded that intracellular PHA played a major role as a carbon source for denitrification in this full-scale UCT process, with a corresponding phosphate uptake also in the anoxic zone. The biological nitrogen and phosphorus removal must, therefore, be regarded as interconnected.

In-mill biological treatment for paper mill closure

The installation of in-mill biological treatment for reducing the concentration of dissolved organic matter and microbial growth in the whitewater system h as been shown to be an interesting alternative for facilitating further closure of paper mill water circuits. In the present study the possibility of operating biological treatment of whitewater from different types of paper production under the environmental conditions prevailing in respective whitewater system, i.e. temperatures between 37 and 52°C and pH-values from 3 to 8. It was shown that high removals of soluble COD, 70-90%, could be achieved even at high temperatures and non-optimal pH-levels. Laboratory scale whitewater systems operated with and without a bioprocess were used for studies of the effect of a bioprocess on key parameters such as slime growth, spore formers and odorous compounds. The introduction of a bioprocess in the whitewater circuit effectively lowered the amount of soluble organic matter and eliminated odorous VFA. However, the operation strategy and control of the bioprocess showed to be crucial, especially the dosing of nutrients, in order to avoid increased rather than decreased biofilm growth in the whitewater system.

Evaluating the Effect of Biofilm Thickness on Nitrification in Moving Bed Biofilm Reactors.

ABSTRACT This study evaluates the effect of biofilm thickness on the nitrifying activity in moving bed biofilm reactors (MBBRs) in a controlled environment. In-depth understanding of biofilm properties in MBBRs and their effect on the overall treatment efficiency is the key to optimizing process stability and efficiency. However, evaluating biofilm properties in continuously operated MBBRs can be extremely challenging. This study uses a carrier design which enables comparison of four different biofilm thicknesses, in otherwise equally operated lab-scale MBBRs. The results show that within the studied range (200–500 µm) and specific operation conditions, biofilm thickness alone had no significant effect on the overall ammonium removal. The nitrate production, however, decreased with a decreasing biofilm thickness, and the ratio between nitrite and ammonia-oxidizing activity decreased both with increasing load and decreasing oxygen concentration for all thicknesses. The suggestion that nitratation is disfavoured in thin biofilms is an interesting contribution to the current research being performed on nitrite-oxidizing bacteria inhibition for deammonification applications. By indicating that different groups of bacteria respond differently to biofilm thickness, this study accentuates the importance of further evaluation of these complex systems.

Carbon and phosphorus transformations in a full-scale enhanced biological phosphorus removal process

Carbon and phosphorus transformations in a full-scale enhanced biological phosphorus removal (EBPR) process was followed during 1 year. A correlation between the soluble phosphorus uptake in the process and the potential substrate for bio-P bacteria, measured as the volatile fatty acid (VFA) potential, in the influent wastewater was found. The results indicated that approximately 20 mg VFA-COD were required to remove 1 mg of soluble phosphorus. In the anaerobic stage of the process, poly-β-hydroxyalcanoic acids (PHA) were produced in an amount of 1.5 mg PHA-COD per mg of VFA-COD taken up by bio-P bacteria. Furthermore, a release of 0.31 mg of phosphate-P per mg of PHA-COD formed was observed in the anaerobic stage. Most of the released phosphate could be accounted for by a decrease in the polyphosphate content of the biomass in the anaerobic stage. Most of the results obtained were very well in agreement with the biochemical model for EBPR suggested by Smolders et al. (1994a).