Roald Kommedal

Quantification of biofilm accumulation by an optical approach

Methods for non-invasive, in situ, measurements of biofilm optical density and biofilm optical thickness were evaluated based on Pseudomonas aeruginosa experiments. Biofilm optical density, measured as intensity reduction of a light beam transmitted through the biofilm, correlates with biofilm mass, measured as total carbon and as cell mass. The method is more sensitive and less labor intensive than other commonly used methods for determining extent of biofilm mass accumulation. Biofilm optical thickness, measured by light microscopy, is translated into physical thickness based on biofilm refraction measurements. Biofilm refractive index was found to be close to the refractive index of water. The P. aeruginosa biofilms studied reached a pseudo steady state in less than a week, with stable liquid phase substrate, cell and TOC concentrations and average biofilm thickness. True steady state was, however, not reached as both biofilm density and roughness were still increasing after 3 weeks.

Estimation of hydrocarbon biodegradation rates in marine environments: a critical review of the Q10 approach.

Offshore oil & gas industry is moving exploration and production activities into Arctic and deep water regions. Governmental regulations require environmental impact assessments before operations to evaluate the possible effects of accidental oil releases. These are often performed by numerical fate models, like the Oil Spill Contingency and Response (OSCAR) model, which has become an industry standard in Norway. In this model, biodegradation rates are adjusted to local conditions by temperature compensation according to a Q10 approach. Q10 is the multiplier by which rates of enzymatic reactions increase at a 10 °C temperature rise. Herein, this Q10 approach implemented in the OSCAR model is investigated based on published data and novel obtained results. Overall, biodegradation rate predictions calculated by temperature compensation are found to be questionable, and choosing one universal Q10 value is considered not feasible. The high variation in Q10 values is herein attributed to indirect effects of temperature.

Protein Phosphatase 2A Holoenzyme Is Targeted to Peroxisomes by Piggybacking and Positively Affects Peroxisomal β-Oxidation

Protein phosphatase 2A targets peroxisomes and positively affects fatty acid oxidation. The eukaryotic, highly conserved serine (Ser)/threonine-specific protein phosphatase 2A (PP2A) functions as a heterotrimeric complex composed of a catalytic (C), scaffolding (A), and regulatory (B) subunit. In Arabidopsis (Arabidopsis thaliana), five, three, and 17 genes encode different C, A, and B subunits, respectively. We previously found that a B subunit, B′θ, localized to peroxisomes due to its C-terminal targeting signal Ser-Ser-leucine. This work shows that PP2A C2, C5, andA2 subunits interact and colocalize with B′θ in peroxisomes. C and A subunits lack peroxisomal targeting signals, and their peroxisomal import depends on B′θ and appears to occur by piggybacking transport. B′θ knockout mutants were impaired in peroxisomal β-oxidation as shown by developmental arrest of seedlings germinated without sucrose, accumulation of eicosenoic acid, and resistance to protoauxins indole-butyric acid and 2,4-dichlorophenoxybutyric acid. All of these observations strongly substantiate that a full PP2A complex is present in peroxisomes and positively affects β-oxidation of fatty acids and protoauxins.

Wastewater characterisation by combining size fractionation, chemical composition and biodegradability

The potential for resource recovery from wastewater can be evaluated based on a detailed characterisation of wastewater. In this paper, results from fractionation and characterisation of two distinct wastewaters are reported. Using tangential flow filtration, the wastewater was fractionated into 10 size fractions ranging from 1 kDa to 1 mm, wherein the chemical composition and biodegradability were determined. Carbohydrates were dominant in particulate size fractions larger than 100 μm, indicating a potential of cellulose recovery from these fractions. While the particulate size fractions between 0.65 and 100 μm show a potential as a source for biofuel production due to an abundance of saturated C16 and C18 lipids. Both wastewaters were dominated by particulate (>0.65 μm), and oligo- and monomeric (<1 kDa) COD. Polymeric (1-1000 kDa) and colloidal (1000 kDa-0.65 μm) fractions had a low COD content, expected due to degradation in the sewer system upstream of the wastewater treatment plant. Biodegradation rates of particulate fractions increase with decreasing size. However, this was not seen in polymeric fractions where degradation rate was governed by chemical composition. Analytical validation of molecular weight and particle size distribution showed below filter cut-off retention of particles and polymers close to nominal cut-off, shifting the actual size distribution.

Environmental Consequences of Polymer Flooding

Worldwide polymer flooding (PF) is being introduced as a viable option for increasing recovery rates. In PF projects, back-produced polymer are ideally disposed of by reinjection or injection to a deposit well. However, significant challenges with offshore produced polymer water management creates possibilities for intermittent overboard discharge. If polymers are released to the sea, then how does structure of the polymers change over time and is it important for the marine ecosystem? In spite of the polymers having very low toxicity, the sheer volume of polymer applied in a PF constitutes a major hazard. In addition, the impact and fate of these polymers are largely unknown beyond standardized acute toxicity and biodegradability data. Very few studies on toxicological mechanisms and long-term environmental fate exist, likely because of lacking analytical tools and incentives for in-depth studies. Currently, biodegradability is decisive for chemical classification within the Norwegian offshore environmental regulations. Biopolymers satisfy the criteria, while the non-biodegradable synthetics do not and are as such prohibited from use. Nonetheless, modern PF favor synthetic polymers due to a variety of factors, including concurrent use of biocide. This together with harsh reservoir conditions favors development of physio-chemically stable polymers, impeding environmental performance and complicating risk management. Moreover, the regulations does not take into account that these polymers are especially sensitive to physical and chemical degradation. To begin solving this puzzle we have set up 80-days inherent and ready biodegradability studies on a variety of partially hydrolyzed polyacrylamide derivatives. Respirometry allows for continuous monitoring of biotic degradation. After the end of the experiment, size exclusion chromatography with multi-angle laser light scattering (MALLS) will examine shifts in molecular weight (Mw) distribution. Regarding MALLS limitation on low concentrations and “dirty” samples, we aim to overcome those by applying ultrafiltration techniques capable of isolating and concentrating the Mw-range of interest. The results will yield structure-activity relationships for both aerobe and anaerobe, biotic and abiotic degradation pathways. Preliminary results show that the presence of synthetic polymer does not affect metabolic rates. Which means that if any degradation is observed, it must be through abiotic mechanisms. This study is a part of a larger effort to generate data forming a basis for a mechanistic model that can predict environmental performance based on polymer chain-length and structure. We believe such a model can be made through mentioned long-term degradation studies, mechanistic eco-toxicological studies and state of the art analytical techniques.

Full-scale experience with enhanced biological phosphorus removal (EBPR) in cold climates

Abstract This investigation includes three years of full‐scale experiences at the first EBPR plant in Norway, Groos WWTP in Grimstad. The main focus was on low temperature performance (below 7 °C) and the effect of wastewater characteristics (COD). The treatment efficiency was not affected by low temperature; 0.35 mg/1 phosphorus in the effluent during 1998 (94 % removal). COD‐levels, however, did affect the process. The results from the study are used as a basis for retrofitting plants that removes phosphorus by chemical precipitation. Results from experiments at a partly retrofitted plant are also presented.