Compositional analysis of Boojum Stanrock and Inco treatment data

The purpose of this investigation has been to consider compositions of water quality data from two mine tailing treatment experiments. These data were assessed for evidence of statistically significant differences as a function of treatment condition, depth and time. The experimental data were obtained as part of studies conducted by Boojum Research Limited that were designed to test the influence of phosphate rock applications with or without amendments of horse manure in controlling acid mine drainage

Fractionation of microbial populations in a PHA accumulating mixed culture and associated PHA content and composition

The uniformity of PHA composition and content across groups of organisms in mixed cultures was considered. An activated sludge microbial community, with an average PHA content of 20 wt%, was fractioned by Percoll assisted buoyant density separation. The microbial community in the two principal fractions was characterised using amplicon pyrosequencing. While organisms were common to both fractions, the relative abundances of species were found to be different between the two fractions. The average PHA content in one of the fractions was found to be higher (24 wt%) than the other (16 wt%); separation was considered to be in part driven by the density difference associated with PHA content, but also by other factors such as cell dimension and cellular morphology. But while differences in PHA content were observed, the PHA composition in both fractions was found to be approximately the same (43-44 mol% HV), which shows that distinct groups of microbial populations within mixed cultures may generate PHA with similar average copolymer composition

Methodological issues in LCA of wastewater treatment combined with PHA biopolymer production

Production of polyhydroxyalkanoates (PHAs) by mixed microbial cultures utilising the organic content of wastewaters is one of the technologies studied in the EU project ROUTES. When comparing the life-cycle environmental impacts of simultaneous wastewater treatment and production of PHA-rich biomass to traditional wastewater and solids treatment, the handling of this multi-functionality is critical for the results. Only one LCA of such a system has been found in the literature. The current paper identifies substitution and allocation based on chemical oxygen demand removal as two possible options to account for the multi-functionality of the system. Examples based on literature data were used to show that for global warming potential, the choice of allocation method can substantially affect the results

Sludge minimization in municipal wastewater treatment by polyhydroxyalkanoate (PHA) production

An innovative approach has been recently proposed in order to link polyhydroxyalkanoates (PHA) production with sludge minimization in municipal wastewater treatment, where (1) a sequencing batch reactor (SBR) is used for the simultaneous municipal wastewater treatment and the selection/enrichment of biomass with storage ability and (2) the acidogenic fermentation of the primary sludge is used to produce a stream rich in volatile fatty acids (VFAs) as the carbon source for the following PHA accumulation stage. The reliability of the proposed process has been evaluated at lab scale by using substrate synthetic mixtures for both stages, simulating a low-strength municipal wastewater and the effluent from primary sludge fermentation, respectively. Six SBR runs were performed under the same operating conditions, each time starting from a new activated sludge inoculum. In every SBR run, despite the low VFA content (10% chemical oxygen demand, COD basis) of the substrate synthetic mixture, a stable feast–famine regime was established, ensuring the necessary selection/enrichment of the sludge and soluble COD removal to 89 %. A good process reproducibility was observed, as also confirmed by denaturing gradient gel electrophoresis (DGGE) analysis of the microbial community, which showed that a high similarity after SBR steady-state had been reached. The main variation factors of the storage properties among different runs were uncontrolled changes of settling properties which in turn caused variations of both sludge retention time and specific organic loading rate. In the following accumulation batch tests, the selected/enriched consortium was able to accumulate PHA with good rate (63 mg CODPHA g CODXa −1h−1) and yield (0.23 CODPHA CODΔS −1) in spite that the feeding solution was different from the acclimation one. Even though the PHA production performance still requires optimization, the proposed process has a good potential especially if coupled to minimization of both primary sludge (by its use as the VFA source for the PHA accumulation, via previous fermentation) and excess secondary sludge (by its use as the biomass source for the PHA accumulation)

Insights into the biodegradation of PHA/wood composites: micro- and macroscopic changes

This study presents a comprehensive analysis of the microscopic and macroscopic changes during the biodegradation of composites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and wood flour (WF) in soil, to provide insights into the biodegradability of this emerging material. Composite samples with different wood contents (0, 20 and 50 wt%) were buried in soil at a field trial site in a subtropical region of Australia, alongside polylactic acid (PLA) and polyethylene (PE) based wood composites as reference. The degradation rate of the PHBV/WF composites increased with wood content, with weight loss after 12 months being five times greater for PHBV/50 wt% WF than for neat PHBV plaques under identical conditions. The mechanical properties of neat PHBV were retained after 12 months of soil burial. However, PHBV/50 wt% WF lost its mechanical integrity after 12 months, despite only a 13% loss in weight. PLA and PE composites by contrast showed only slight decreases in mechanical properties, which could be associated with moisture induced degradation at the surface only. It is proposed, with evidence from optical microscopy, that for the PHBV-based samples, localised stress loosened the interface, allowing channels for the bacteria and fungi to access PHBV in the bulk of the matrix for local enzymatic biodegradation. With this network of interconnecting pores and cracks, crack propagation and mechanical failure would readily result from an applied stress. Overall, although the erosion rate for the exposed PHBV surfaces in the different samples could be similar, the accessible surface area in PHBV/50 wt% WF composites is significantly larger following local biodegradation and subsequent void formation than for neat PHBV and thus delivers a higher biodegradation rate

Insights into the biodegradation of PHA/wood composites: micro- and macroscopic changes

This study presents a comprehensive analysis of the microscopic and macroscopic changes during the biodegradation of composites of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and wood flour (WF) in soil, to provide insights into the biodegradability of this emerging material. Composite samples with different wood contents (0, 20 and 50 wt%) were buried in soil at a field trial site in a subtropical region of Australia, alongside polylactic acid (PLA) and polyethylene (PE) based wood composites as reference. The degradation rate of the PHBV/WF composites increased with wood content, with weight loss after 12 months being five times greater for PHBV/50 wt% WF than for neat PHBV plaques under identical conditions. The mechanical properties of neat PHBV were retained after 12 months of soil burial. However, PHBV/50 wt% WF lost its mechanical integrity after 12 months, despite only a 13% loss in weight. PLA and PE composites by contrast showed only slight decreases in mechanical properties, which could be associated with moisture induced degradation at the surface only. It is proposed, with evidence from optical microscopy, that for the PHBV-based samples, localised stress loosened the interface, allowing channels for the bacteria and fungi to access PHBV in the bulk of the matrix for local enzymatic biodegradation. With this network of interconnecting pores and cracks, crack propagation and mechanical failure would readily result from an applied stress. Overall, although the erosion rate for the exposed PHBV surfaces in the different samples could be similar, the accessible surface area in PHBV/50 wt% WF composites is significantly larger following local biodegradation and subsequent void formation than for neat PHBV and thus delivers a higher biodegradation rate

The effect of pH on microbial activity and community structure in the biological removal of resin acids from wastewater

Pulp mills in Canada rely on biological treatment systems for the removal of resin acids that are released from wood during pulping and bleaching. These are priority contaminants for the pulping industry, since they have been frequently associated with events of toxicity breakthrough. Although, tighter mill control has helped to minimize the losses of resin acids in wastewater, acute toxicity removal in downstream biological treatment systems may still be insufficient, particularly under dynamic loading conditions. The mechanisms responsible for these limitations are not fully understood. This dissertation documents a fundamental study into the fate of resin acids during biological treatment. The objective was to quantify the influence of pH on the resin acid bioavailability, metabolism, and retention time during biological treatment. A progression of two batch and two continuous flow bioreactor investigations were undertaken to consider the interrelated issues of pH-dependent microbial activity and resin acid hydrophobicity. Changes in pH, within the typical range for biological treatment, significantly altered the bioavailability of resin acids and the community of microorganisms responsible for resin acid biodegradation. A sudden input of resin acids promoted an elevated level of community change during continuous treatment of bleached kraft mill effluent. The capacity of a treatment system to remove resin acids was found to be a function of the contaminant loading history. Time lag before biological removal in response to a shift-up in resin acid loading was significant and was also affected by the treatment system pH. Hence, the prevailing bioreactor pH operating condition, in conjunction with the period and amplitude of loading transients were shown to be key aspects controlling the microbial community structure and physiological state, which in turn determine the rate and extent of biological removal of resin acids. Through the course of the four investigations, novel contributions have been made in the areas of surface tension and microbial fatty acid measurements that have engineering application in future modelling and monitoring of the behaviour of microbial wastewater treatment processes.Applied Science, Faculty ofCivil Engineering, Department ofGraduat

The production of biopolymers for bioplastics using pulp and paper mill wastewater and residual fibre streams

As part of the Multibio project, the potential for production of biobased and biodegradable polymers, from organic residuals in process effluent streams, was evaluated for Stora Enso Skoghalls and Rottneros pulp and paper mills in Värmland, Sweden.   These biopolymers are thermoplastic polyesters made by naturally occurring bacteria and are from the family of polyhydroxyalkanoates (PHAs).  They can be formulated as principal ingredients for plastics, functional chemicals, and composite materials of interest to a diversity of sectors including the pulp and paper industry.  They can also be formulated into fish feed to impart pre/pro-biotic benefits in aquaculture.  Commercial quantities and qualities of PHAs can be produced as a corollary benefit to biological wastewater treatment processes that are used to treat industrial and municipal wastewaters for environmental protection.  The goal of the present study has been to determine the potential quantities of PHA that could be produced as an integral part of the mill residual organics and effluent management.  The aim of this Multibio work package has also been to recommend steps forward. It was estimated that Skoghalls and Rottneros mills manage 70 and 15 tons per day of residual organic material on a chemical oxygen demand (COD) basis, and in relation to respective production levels of about 778,000 and 170,000 ton/yr paper and board.  These numbers were calculated from mass balances using historical monitoring information provided by the mills and with measurements made in this study on samples from selected locations of the treatment processes.  The residual COD is comprised of fibre and surplus activated sludge as well as soluble dissolved organic material.  This organic material is a resource to produce a microbial biomass rich in PHA with remaining organic material being used for boiler heat production.   Improved sludge dewatering is expected such that COD used for heat production today could be diverted to PHA without undue loss of heat production capacity in the balance. Two process scenarios are presented (Scenario 1 & 2) as a logical progression of risk and development.  PHA production requires that some organic feedstock is first converted into volatile fatty acids (VFAs) through acidogenic fermentation.  If all the residual organic mass is used to produce VFAs (Scenario 1), it was estimated that about 2 000 and 400 tons PHA per year could be produced at Skoghalls and Rottneros mills, respectively.  Production amounts would be increased (Scenario 2) by about 50 % (3 000 and 600 tPHA/yr, respectively) if the residual mass flows of waste activated sludge biomass from the mill aerobic biological wastewater treatment processes could be exploited for a PHA storing potential rather than just being an organic feedstock to yield VFAs.   A mill side-line of polymer production anchors in-house supply and experience with PHAs while casting a net for evolving and capturing future interesting materials and business.  Future mill economies may foreseeably require standing on wider business footings including fibre as well as from other cellulose derived biobased revenue generating products and services.  PHAs can naturally also be made using the prime input lumber starting with hemicellulose and cellulose.  Opening a PHA specialty industry first is a way to open the door for discovery that may well motivate directing strategically separated mill upstream organic fractions to successful large commercial revenues from PHAs in the future.  Som en del av projektet Multibio har potentialen att producera biobaserade och biologiskt nedbrytbara polymerer från organiska rester i processavloppsvatten utvärderats vid Stora Enso Skoghalls och Rottneros pappers- och massabruk i Värmland, Sverige. Dessa polymerer är termoplastiska polyestrar som produceras av naturligt förekommande bakterier och tillhör gruppen polyhydroxyalkanoater (PHA). De kan formuleras som huvudingrediens i plaster, funktionella kemikalier och kompositmaterial relevanta för vitt skilda sektorer inklusive skogsindustrin. De kan också användas som ingrediens i fiskfoder för att åstadkomma en pre/pro-biotisk effekt vid fiskodling. Kommersiellt relevanta mängder och kvaliteter av PHA kan produceras som en bi-produkter vid den biologiska vattenrening som används för att behandla industriella och kommunala processavloppsvatten. Målet med denna studie har varit att bestämma de potentiella mängder av PHA som skulle kunna produceras som en integrerad del av brukens hantering och behandling av restströmmar. Syftet med denna del av Multibioprojektet har även varit att ge rekommendationer för en fortsatt stegvis utveckling. Tillgängliga restströmmar vid Skoghalls och Rottneros bruk uppskattas motsvarar 70 respektive 15 ton per dag angivet som kemiskt syrebehov (COD, ”chemical oxygen demand”). Siffrorna beräknades med en massbalans baserad på historiska data från bruken samt analyser av stickprov från olika delar av reningsprocesserna. Restströmmarnas COD består av fiber, överskottsbioslam och löst organiskt material. Detta organiska material skulle kunna användas som råvara för att producera en mikrobiell biomassa rik på PHA med en återstående mängd som kan förbrännas för värmeproduktion. Förbättrad slamavvattning kan antas.  På så sätt varje ton COD som används för PHA-produktion orsakar en minskning i värmeproduktion som är mindre än vad som annars vore fallet.   Två scenarier presenteras. För att producera PHA behöver först en del av organiska råvaran omvandlas till flyktiga fettsyror (VFA, ”volatile fatty acids”) genom acidogen fermentering. Om alla tillgängliga organiska rester används för att producera VFA (Scenario 1), uppskattades att ungefär 2 000 respektive 400 ton PHA per år skulle kunna produceras vid Skoghalls och Rottneros bruk. De producerade mängderna skulle öka med ungefär 50 % (3 000 respektive 600 ton PHA/år), ifall överskottsbioslammet från brukens processvattenrening kunde utnyttjas för att producera PHA istället för att endast vara en råvara för VFA (Scenario 2).     Baserat på erfarenheter från liknande fall kan det förväntas att en liten produktion av polymerer förankrar egna erfarenheter av materialen och deras produktion samtidigt som en krok agnas för att fånga framtida vidare utveckling. Den framtida ekonomin för pappers- och massabruk förväntas kräva en bredare affärsmodell med fiber såväl som andra biobaserade produkter och tjänster. PHA kan även produceras från själva vedråvaran utifrån hemicellulosa och cellulosa. Att starta en nisch-tillverkning av PHA kan vara ett sätt att möjliggöra upptäckter som mycket väl kan motivera att vissa fraktioner av bruken huvudråvaror används för nya material såsom PHA.This report disseminates part of the activities and development made through work package 2 of the project 'MultiBio: A multipurpose biorefinery in a pulp and paper industry' financed by Sweden’s innovation agency Vinnova. Miljötjänster från ett multifunktionellt bioraffinader

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