Carbon Usage Research Articles

Decarbonisation perspectives for the Polish economy

In the coming decades the energy sector in Poland will undergo a substantial transition towards low carbon usage, which will have a predominant impact on the economy. Several modernization scenarios for energy policy are currently being discussed by the government and not yet concluded. The main objective of this paper is to provide a tool that allows to simulate such scenarios and to show the impact of decarbonisation on the whole economy. We propose an intertemporal hybrid general equilibrium modeling that incorporates energy technologies (bottom-up approach) directly into a macroeconomic structure (top-down approach). By accounting for wide adjustments in the economy, while controlling for all major constraints, the model gives a unique and detailed insight into the future shape of the energy sector and prospects of low carbon economy in Poland. Our simulation results suggest that there are no free lunches. No realistic energy mix allows to achieve sustainable positive economic growth when considerable emission reduction is to be achieved. The price on CO2 will exceed EUR 100 for 30% emission reduction with respect to business-as-usual scenario. Gradual phase-out of coal requires focusing on biomass technology (the first best), nuclear and wind power (the second best).

Plaster composites modified morphology with enhanced compressive strength and water resistance characteristics

Due increasing attention for non-conventional building materials, modified gypsum plaster composites were studied to assess their water resistance when blended with different additives and their effect on the strength properties. The plaster-composites were formed by dry mixing of fine or ultrafine sand, silica fume, silica gel, rice husk, slag, calcium carbonate or polyvinyl acetate (PVA). Their phase composition was investigated using FTIR and XRD with crystallite size data to be correlated with their microstructure morphologies as elucidated by SEM for the air- and water-cured samples.Results clarified that the morphology and some grain dimensions of set plaster composites have changed leading to improve their compressive strength and water resistance. The set plaster grain dimensions altered from long acicular crystals to short compact thin one. Composites with almost all additives reveal resistance to water whereas silica gel showed lower effect, due to its higher affinity to humidity. The compressive strength and softening coefficient of the water-cured plaster-slag composite increased by about 30% compared with air-cured blank sample due to the hydration of slag in gypsum composite matrix. Either calcium carbonate or PVA usage (3 wt%) in gypsum composites improved the compressive strength by about 14 and 19% of water cured samples, respectively. The synthesized plaster composites are promising building units for various applications when lightweight, high porosity, water resistant building units are needed.

Intraspecies polymorphisms of Kluyveromyces marxianus strains from Yaghnob valley

In this study, 29 strains of Kluyveromyces marxianus with peculiar genetic and phenotypic traits previously isolated from a fermented goat milk of Yaghnob valley were investigated for chromosome length polymorphism (CLP) by PFGE, adhesion properties and carbon usage by Biolog analysis. Obtained data showed that strains differed in terms of number and size of chromosome bands. The number of bands ranged from 5 to 7, suggesting a probable genome size from 1.4 to 2.6 Mb. Strains showed a certain level of cell surface hydrophobicity ranging from 32% to 77.7%. Strains were also tested for their ability to form a biofilm on polystyrene plates: planktonic cells ranged from 6.3 cfu/mL to 7.95 cfu/mL, while sessile from 7.11 cfu/mL to 8.6 cfu/mL. The strains able to adhere to polystyrene plates were also able to form a mature MAT. Biolog analysis revealed that almost all strains were able to use putrescine, malic acid, α-D lactose, phenylethylamine, β-methyl D-gucoside and xylose; 5 strains were able to grow on cellobiose and 3 were able to catabolise α-ketobutyric. The obtained data highlighted a number of interesting features underlying the peculiar capacities of these strains for industrial applications.

Performance and emission analysis of a naturally aspirated and supercharged IDI diesel engine using palm methyl ester

ABSTRACTTests were conducted on a naturally aspirated and supercharged Indirect Diesel Injection (IDI) diesel engine. An automobile version was used in this experiment, with neat palm biodiesel replacing the diesel fuel. Naturally aspirated and supercharged engine conditions were tallied in the light of the performance and emission evaluation with diesel fuel. Thermal efficiency suffered by 5.28% when the engine is supercharged at maximum load, and it was reduced by 2.94% at 3/4 of the maximum load. This percentage reduction progressively decreased as the load on the engine decreased. There is an obvious increase in the specific fuel consumption with the supercharged engine but it is justified with the increase in the power output. When emissions were measured, the supercharged engine performed better than the naturally aspirated engine. Hydrocarbon and NOx levels were reduced at the top two loads by more than 2 ppm and more than 100 ppm, respectively. CO levels decreased significantly. CO2 levels decreased by 5.92% and 4.1% at the two upper loads, respectively. There is a simultaneous decrease in CO2 and smoke levels, indicating better usage of carbon.

Advances in cyanobacterial polyhydroxyalkanoates production.

Polyhydroxyalkanoates (PHAs) have received much attention in the current scenario due to their attractive material properties, namely biodegradability, biocompatibility, thermoplasticity, hydrophobicity, piezoelectricity and stereospecificity. All these properties make them highly competitive for various industrial applications similar to non-degradable conventional plastics. In PHA biosynthesis, PHA synthase acts as a natural catalyst for PHA polymerization process using the (R)-hydroxyacyl-CoA as substrate. Cyanobacteria can accumulate PHAs under photoautotrophic and/or mixotrophic growth conditions with organic substrates such as acetate, glucose, propionate, valerate, and so on. The natural incidence of PHA accumulation by the cyanobacteria is known since 1966. Nevertheless, PHA accumulation in cyanobacteria based on the cell biomass and volumetric productivity is critically lower than the heterotrophic bacteria. Consequently, cyanobacteria are nowadays not considered for commercial production of PHAs. Thus, strain improvements by genetic modification, new cultivation and harvesting techniques, advanced photobioreactor development, efficient and sustainable downstream processes, alternate economical carbon sources and usage of various metabolic inhibitors are suggested for enhancing cyanobacterial PHA accumulation. In addition, identification of transcriptional regulators like RNA polymerase sigma factor (SigE) and a response regulator (Rre37) together with the recent major scientific breakthrough on the existence of complete Krebs cycle in cyanobacteria would be helpful in taking PHA production from cyanobacteria to a new-fangled height in near future.

Removal of Microcystin-LR from Drinking Water Using a System Involving Oxidation and Adsorption

The aim of the present study was to evaluate the efficiency of removal of microcystin-LR from drinking water using a three-stage bench-scale treatment comprising Fenton oxidation/coagulation/flocculation/sedimentation, filtration through a sand column (15 cm bed), and adsorption onto a granular activated carbon (GAC) column with 15-cm (GAC1) or 20-cm bed (GAC2). Optimal first-stage conditions were determined to be FeSO4∙7H2O 0.054 mM, H2O2 0.162 mM, coagulation pH 8.4, sedimentation time 15 min, and flow rate 2 L h−1. Under these conditions, water turbidity was reduced from 5.8 to 3.0 uT, apparent color from 115 to 81 uH, and the concentration of microcystin-LR from 18.52 to 9.59 μg L−1. Column GAC2 was more efficient than GAC1, as shown by the higher adsorption capacity (4.15 μg g−1) and lower carbon usage rate (1.70 g L−1). Microcystin breakthrough occurred after 2 h of operation with GAC1 column and after 6 h with GAC2 column, and the greater efficiency of the latter column was confirmed by the high qe (4.15 μg g−1) and low CUR (1.70 g L−1) values attained. The results demonstrate that adsorption on a GAC column plays an essential role in reducing the concentration of microcystin-LR to levels compatible with current legislation. By-products of the Fenton oxidation of microcystin-LR were analyzed by mass spectrometry, and the ADDA amino acid present in the analyte was identified from its characteristic fragment at m/z 135. It is concluded that the combination of Fenton oxidation and adsorption on a GAC column represents a viable option for purifying eutrophic water containing high concentrations of microcystin-LR.

Engineering high-level production of fatty alcohols by Saccharomyces cerevisiae from lignocellulosic feedstocks

Fatty alcohols in the C12-C18 range are used in personal care products, lubricants, and potentially biofuels. These compounds can be produced from the fatty acid pathway by a fatty acid reductase (FAR), yet yields from the preferred industrial host Saccharomyces cerevisiae remain under 2% of the theoretical maximum from glucose. Here we improved titer and yield of fatty alcohols using an approach involving quantitative analysis of protein levels and metabolic flux, engineering enzyme level and localization, pull-push-block engineering of carbon flux, and cofactor balancing. We compared four heterologous FARs, finding highest activity and endoplasmic reticulum localization from a Mus musculus FAR. After screening an additional twenty-one single-gene edits, we identified increasing FAR expression; deleting competing reactions encoded by DGA1, HFD1, and ADH6; overexpressing a mutant acetyl-CoA carboxylase; limiting NADPH and carbon usage by the glutamate dehydrogenase encoded by GDH1; and overexpressing the Δ9-desaturase encoded by OLE1 as successful strategies to improve titer. Our final strain produced 1.2g/L fatty alcohols in shake flasks, and 6.0g/L in fed-batch fermentation, corresponding to ~ 20% of the maximum theoretical yield from glucose, the highest titers and yields reported to date in S. cerevisiae. We further demonstrate high-level production from lignocellulosic feedstocks derived from ionic-liquid treated switchgrass and sorghum, reaching 0.7g/L in shake flasks. Altogether, our work represents progress towards efficient and renewable microbial production of fatty acid-derived products.

Implications of nitrogen phloem loading for carbon metabolism and transport during Arabidopsis development.

Metabolite transport processes and primary metabolism are highly interconnected. This study examined the importance of source-to-sink nitrogen partitioning, and associated nitrogen metabolism for carbon capture, transport and usage. Specifically, Arabidopsis aap8 (AMINO ACID PERMEASE 8) mutant lines were analyzed to resolve the consequences of reduced amino acid phloem loading for source leaf carbon metabolism, sucrose phloem transport and sink development during vegetative and reproductive growth phase. Results showed that decreased amino acid transport had a negative effect on sink development of aap8 lines throughout the life cycle, leading to an overall decrease in plant biomass. During vegetative stage, photosynthesis and carbohydrate levels were decreased in aap8 leaves, while expression of carbon metabolism and transport genes, as well as sucrose phloem transport were not affected despite reduced sink strength. However, when aap8 plants transitioned to reproductive phase, carbon fixation and assimilation as well as sucrose partitioning to siliques were strongly decreased. Overall, this work demonstrates that phloem loading of nitrogen has varying implications for carbon fixation, assimilation and source-to-sink allocation depending on plant growth stage. It further suggests alterations in source-sink relationships, and regulation of carbon metabolism and transport by sink strength in a development-dependent manner.

Comparing test methods for granular activated carbon for organic micropollutant elimination

Adsorption onto granular activated carbon (GAC) is an effective treatment step for the removal of organic micropollutants (OMP) from wastewater or drinking water. Different test methods are commonly used for evaluating the capability of a GAC depending on the raw material and activation method. Several of these methods have been tested with one GAC and different size fractions obtained by grinding and sieving: batch experiments with two distinct modes of agitation (magnetic stirring and horizontal agitation), laboratory-scale adsorbers (LSA), rapid small-scale column tests (RSSCT) and differential column batch reactors (DCBR). It was found that magnetically stirred batches and DCBR are well suited for minimizing the effects of film diffusion. However, magnetic stirring reduces the particle size especially for large grains and long experimental periods. For fixed-bed adsorbers (LSA and RSSCT), it was shown that increasing the contact time of the water with the GAC at high throughputs can significantly improve the removal of OMP even after 100,000 bed volumes. However, permeability losses in RSSCT even with tap water have to be considered as a severe drawback. Correlations have been established between the loading achieved in a batch after 24h and the carbon usage rate (CUR) at which the same loading was reached in an RSSCT. As expected, RSSCT removed OMP more efficiently than batch experiments at the same CUR.

Pilot-scale removal of pharmaceuticals in municipal wastewater: Comparison of granular and powdered activated carbon treatment at three wastewater treatment plants

Adsorption with activated carbon is widely suggested as an option for the removal of organic micropollutants including pharmaceutically active compounds (PhACs) in wastewater. In this study adsorption with granular activated carbon (GAC) and powdered activated carbon (PAC) was analyzed and compared in parallel operation at three Swedish wastewater treatment plants with the goal to achieve a 95% PhAC removal. Initially, mapping of the prevalence of over 100 substances was performed at each plant and due to low concentrations a final 22 were selected for further evaluation. These include carbamazepine, clarithromycin and diclofenac, which currently are discussed for regulation internationally. A number of commercially available activated carbon products were initially screened using effluent wastewater. Of these, a reduced set was selected based on adsorption characteristics and cost. Experiments designed with the selected carbons in pilot-scale showed that most products could indeed remove PhACs to the target level, both on total and individual basis. In a setup using internal recirculation the PAC system achieved a 95% removal applying a fresh dose of 15–20 mg/L, while carbon usage rates for the GAC application were much broader and ranged from <28 to 230 mg/L depending on the carbon product. The performance of the PAC products generally gave better results for individual PhACs in regards to carbon availability. All carbon products showed a specific adsorption for a specific PhAC meaning that knowledge of the target pollutants must be acquired before successful design of a treatment system. In spite of different configurations and operating conditions of the different wastewater treatment plants no considerable differences regarding pharmaceutical removal were observed.

Dynamic Repositioning to Reduce Lost Demand in Bike Sharing Systems

Bike Sharing Systems (BSSs) are widely adopted in major cities of the world due to concerns associated with extensive private vehicle usage, namely, increased carbon emissions, traffic congestion and usage of nonrenewable resources. In a BSS, base stations are strategically placed throughout a city and each station is stocked with a pre-determined number of bikes at the beginning of the day. Customers hire the bikes from one station and return them at another station. Due to unpredictable movements of customers hiring bikes, there is either congestion (more than required) or starvation (fewer than required) of bikes at base stations. Existing data has shown that congestion/starvation is a common phenomenon that leads to a large number of unsatisfied customers resulting in a significant loss in customer demand. In order to tackle this problem, we propose an optimisation formulation to reposition bikes using vehicles while also considering the routes for vehicles and future expected demand. Furthermore, we contribute two approaches that rely on decomposability in the problem (bike repositioning and vehicle routing) and aggregation of base stations to reduce the computation time significantly. Finally, we demonstrate the utility of our approach by comparing against two benchmark approaches on two real-world data sets of bike sharing systems. These approaches are evaluated using a simulation where the movements of customers are generated from real-world data sets.

The occurrence of enhanced biological phosphorus removal in a 200,000 m3/day partial nitration and Anammox activated sludge process at the Changi water reclamation plant, Singapore.

Mainstream partial nitritation and Anammox (PN/A) has been observed and studied in the step-feed activated sludge process at the Changi water reclamation plant (WRP), which is the largest WRP (800,000 m3/d) in Singapore. This paper presents the study results for enhanced biological phosphorus removal (EBPR) co-existing with PN/A in the activated sludge process. Both the in-situ EBPR efficiency and ex-situ activities of phosphorus release and uptake were high. The phosphorus accumulating organisms were dominant, with little presence of glycogen accumulating organisms in the activated sludge. Chemical oxygen demand (COD) mass balance illustrated that the carbon usage for EBPR was the same as that for heterotrophic denitrification, owing to autotrophic PN/A conversions. This much lower carbon demand for nitrogen removal, compared to conventional biological nitrogen removal, made effective EBPR possible. This paper demonstrated for the first time the effective EBPR co-existence with PN/A in the mainstream in a large full-scale activated sludge process, and the feasibility to accommodate EBPR into the mainstream PN/A process. It also shows EBPR can work under warm climates.

ENVIRONMENTAL TAXATION IN THE UK: THE CLIMATE CHANGE LEVY AND POLICY MAKING

Environmental taxation is different from many other forms of taxation as it is not only used to raise revenue but it is also able to marginally influence behaviour to protect and enhance the environment. It provides valuable market led mechanisms to help limit greenhouse gas emissions, encourage sustainable behaviour and improve environmental performance to address climate change. The Post Paris (COP21) agreement provides a framework for global actions to address climate change and this sets the context for the discussion of environmental taxation.Environmental taxes have enormous potential to change carbon usage. In 2012, the Coalition Government (2010-2015) opined that the definition of an environmental tax includes three principles, namely that the tax is explicitly linked to the government’s environmental objectives, that the primary objective of the tax is to encourage environmentally positive behaviour, and that the tax is structured in relation to environmental objectives, particularly the more polluting the behaviour the greater tax levied. The current Government has adopted and applied this definition. By way of contrast, the definitions of environmental taxation favoured by the Office for National Statistics (ONS) and the Organisation for Economic Cooperation and Development (OECD), respectively, give a wider remit for environmental taxation and policy making and include, for instance, various transport taxes which, as will be seen, do not fall within the Government’s definition of an environmental tax. The Climate Change Levy, which is the focus of this article, was introduced as one of a series of new environmental taxes on business energy use in 2001. It is charged on electricity, gas liquefied petroleum gas and solid fuels used by business.Generally, environmental taxes are intended to increase investments in renewable technologies while reducing carbon emissions, but they are vulnerable to political influence and policy changes. Thus, the rationale for environmental or ‘Green’ taxes has shifted perceptibly to raising revenue rather than enabling government to meet its obligations under the Climate Change Act 2008. Environmental taxes are also susceptible to oil prices and fluctuations in the global economy. The North Sea oil and gas industry is going through a difficult period of retrenchment. A recent independent report has suggested that the industry has two years to adjust to changing economic circumstances. Inevitably, this will impact on the tax revenues raised from this sector.In an ideal world, environmental taxes should be easy to avoid through a change in behaviour and, consequently, hard to evade. Environmental taxes provide important means to achieve policy objectives, but their full potential requires public support and, especially, engagement by the business community. The future of environmental taxes may depend on the success of ‘green’ investment. There is a case for introducing a single climate tax on business. Undoubtedly, environmental taxes deserve greater attention in the economic toolbox to meet climate change commitments. The UK faces some difficult policy decisions under the Climate Change Act 2008 to meet the 2030 energy and climate change package targets. Currently, the UK receives 7.5 % of tax revenue from environmental taxes. To date, environmental taxation has had mixed outcomes in the UK, though few doubt its potential to define the future of carbon based energy use.

Analysis of respiratory activity and carbon usage of a mutant of Azotobacter vinelandii impaired in poly-β-hydroxybutyrate synthesis.

In this study, the respiratory activity and carbon usage of the mutant strain of A. vinelandii AT6, impaired in poly-β-hydroxybutyrate (PHB) production, and their relationship with the synthesis of alginate were evaluated. The alginate yield and the specific oxygen uptake rate were higher (2.5-fold and 62%, respectively) for the AT6 strain, compared to the control strain (ATCC 9046), both in shake flasks cultures and in bioreactor, under fixed dissolved oxygen tension (1%). In contrast, the degree of acetylation was similar in both strains. These results, together with the analysis of carbon usage (% C-mol), suggest that in the case of the AT6 strain, the flux of acetyl-CoA (precursor molecule for PHB biosynthesis and alginate acetylation) was diverted to the respiratory chain passing through the tricarboxylic acids cycle, and an important % C-mol was directed through alginate biosynthesis, up to 25.9% and to a lesser extent, to biomass production (19.7%).

Feasibility of treating emulsified oily and salty wastewaters through coagulation and bio-regenerated GAC filtration

In the present study, chemical oxygen demand (COD) removal by coagulation and packed-columns of both fresh and bioregenerated granular activated carbon (GAC) is reported as a feasible treatment for saline and oily wastewaters (slops) generated from marine oil tankers cleaning. The use of Ferric chloride (FeCl3), Aluminium sulphate (Al2(SO4)3) and Polyaluminum chloride (Al2(OH3)Cl3) was evaluated in the pre-treatment by coagulation of a real slop, after a de-oiling phase in a tank skimmer Comparison of coagulation process indicated that Polyaluminum chloride and Aluminium sulphate operate equally well (20–30% of COD removal) when applied at their optimal dose (40 and 90 mg/l respectively) but the latter should be preferred in order to significantly control the sludge production. The results from the column filtration tests indicated the feasibility of using the selected GAC (Filtrasorb 400 -Calgon Carbon Corporation) to achieve the respect of the discharge limits in the slops treatment with a carbon usage rate in the range 0.1–0.3 kg/m3 of treated effluent. Moreover, biological regeneration through Alcalinovorax borkumensis SK2 was proved to be a cost-effective procedure since the reuse of spent GAC through such regeneration process for further treatment could still achieve approximately 90% of the initial sorption capacity, reducing then costs for the use of new sorbents and also the need for waste disposal.

Biomass and activity soil microorganisms in grazing and secondary forests areasA

Sustainable livestock production generates benefits for the environment, such as water capture, increased biodiversity and carbon dioxide capture. To measure these factors in a tropical setting, in 2007 we took three samples of a milk production system in Turrialba, Cartago, Costa Rica, in areas with permanent African Star grass cover (under grazing) and a secondary forest with 15 years of regeneration. We estimated carbon content in the microbial biomass, microbial activity (breathing technique), carbon usage profile (BIOLOG ECOPLATES®) and functional diversity of microorganisms (Shannon index). Biomass carbon in the pasture was 3,3 times higher than in the forest, but microbial activity was similar. Carbon use rate ranged from 22,22 to 85,19% in the pasture (higher in the forest: 29,63 to 92,59%). In both areas growth correlated with incubation time, but the forest had more biodiversity. Pasture areas are favored by carbon deposition to the rhizosphere, while the variety of vegetation in the forest allows greater functional diversity in the use of carbon substrates.

Sevelamer Carbonate and Lanthanum Usage Evaluation and Cost Considerations at a Veteran's Affairs Medical Center.

Hyperphosphatemia is a common problem in patients with chronic kidney disease (CKD). Calcium-containing phosphate binders are typically used as first-line therapy, primarily due to cost considerations. Non-calcium phosphate binders such as sevelamer and lanthanum may be considered in the appropriate setting. It is hypothesized that lanthanum is less costly and has a lower pill burden compared to sevelamer carbonate. Determine the difference in cost (outcome 1) and tablet burden (outcome 2) between sevelamer carbonate and lanthanum within the Veteran population. Patients with an active prescription for lanthanum or sevelamer carbonate on October 22, 2014 were evaluated. Chi-square analysis was used to analyze categorical data, and 2-sided t test was used for continuous data. An α of 0.05 determined significance. One hundred fifty patients were included in the evaluation. Patients were predominately male (96%) and had a diagnosis of end stage renal disease (ESRD; 78%). The combined rate of non-dialysis CKD (ND-CKD) stage 5 and ESRD was similar between lanthanum and sevelamer carbonate groups. Both groups achieved similar phosphorus control (56% vs 65%, with phosphorus level less than or equal to 5.5 mg/dL, respectively; P = .23). Lanthanum prescriptions required significantly fewer tablets per day (4 lanthanum tablets daily vs 7 sevelamer carbonate tablets daily; P < .001). A potential prescription cost savings of approximately $4,500 monthly or $54,000 annually was seen when considering conversion of patients in this study population from sevelamer carbonate to lanthanum therapy, with appreciable savings beginning at sevelamer daily doses of at least 4,800 mg. Compared to sevelamer carbonate, lanthanum use was associated with reduced pill burden and lower absolute drug cost while maintaining similar phosphorus control.

Study on Ion-Conducting Properties of Ionic Liquid Containing Carbonate Electrolytes Against Carbon Electrode.

The ionic performances for the mixture of ethylene carbonate (EC) and dimethylcarbonate (DMC) were investigated for supercapacitor electrolyte. The usage of ethylene carbonate (EC) and dimethylcarbonate (DMC) as organic solvent could solve some problems of acetonitrile (AN). The general aim of present paper is compare to properties of electrochemical properties based on two mixed organic electrolytes. The ionic conductivity, viscosity, and electrochemical performances of EC/DMC+0.1 M TEABF4 mixtures were determined. The ionic conductivity of the electrolytes was measured by AC impedance, and the capacitative performances of the electrolytes were evaluated by using cyclic voltammetry.

A Specific Transcriptome Signature for Guard Cells from the C4 Plant Gynandropsis gynandra.

C4 photosynthesis represents an excellent example of convergent evolution that results in the optimization of both carbon and water usage by plants. In C4 plants, a carbon-concentrating mechanism divided between bundle sheath and mesophyll cells increases photosynthetic efficiency. Compared with C3 leaves, the carbon-concentrating mechanism of C4 plants allows photosynthetic operation at lower stomatal conductance, and as a consequence, transpiration is reduced. Here, we characterize transcriptomes from guard cells in C3 Tareneya hassleriana and C4 Gynandropsis gynandra belonging to the Cleomaceae. While approximately 60% of Gene Ontology terms previously associated with guard cells from the C3 model Arabidopsis (Arabidopsis thaliana) are conserved, there is much less overlap between patterns of individual gene expression. Most ion and CO2 signaling modules appear unchanged at the transcript level in guard cells from C3 and C4 species, but major variations in transcripts associated with carbon-related pathways known to influence stomatal behavior were detected. Genes associated with C4 photosynthesis were more highly expressed in guard cells of C4 compared with C3 leaves. Furthermore, we detected two major patterns of cell-specific C4 gene expression within the C4 leaf. In the first, genes previously associated with preferential expression in the bundle sheath showed continually decreasing expression from bundle sheath to mesophyll to guard cells. In the second, expression was maximal in the mesophyll compared with both guard cells and bundle sheath. These data imply that at least two gene regulatory networks act to coordinate gene expression across the bundle sheath, mesophyll, and guard cells in the C4 leaf.

Combination of granular activated carbon adsorption and deep-bed filtration as a single advanced wastewater treatment step for organic micropollutant and phosphorus removal

Adsorption onto granular activated carbon (GAC) is an established technology in water and advanced wastewater treatment for the removal of organic substances from the liquid phase. Besides adsorption, the removal of particulate matter by filtration and biodegradation of organic substances in GAC contactors has frequently been reported. The application of GAC as both adsorbent for organic micropollutant (OMP) removal and filter medium for solids retention in tertiary wastewater filtration represents an energy- and space saving option, but has rarely been considered because high dissolved organic carbon (DOC) and suspended solids concentrations in the influent of the GAC adsorber put a significant burden on this integrated treatment step and might result in frequent backwashing and unsatisfactory filtration efficiency. This pilot-scale study investigates the combination of GAC adsorption and deep-bed filtration with coagulation as a single advanced treatment step for simultaneous removal of OMPs and phosphorus from secondary effluent. GAC was assessed as upper filter layer in dual-media downflow filtration and as mono-media upflow filter with regard to filtration performance and OMP removal. Both filtration concepts effectively removed suspended solids and phosphorus, achieving effluent concentrations of 0.1 mg/L TP and 1 mg/L TSS, respectively. Analysis of grain size distribution and head loss within the filter bed showed that considerable head loss occurred in the topmost filter layer in downflow filtration, indicating that most particles do not penetrate deeply into the filter bed. Upflow filtration exhibited substantially lower head loss and effective utilization of the whole filter bed. Well-adsorbing OMPs (e.g. benzotriazole, carbamazepine) were removed by >80% up to throughputs of 8000–10,000 bed volumes (BV), whereas weakly to medium adsorbing OMPs (e.g. primidone, sulfamethoxazole) showed removals <80% at <5,000 BV. In addition, breakthrough behavior was also determined for gabapentin, an anticonvulsant drug recently detected in drinking water resources for which suitable removal technologies are still largely unknown. Gabapentin showed poor adsorptive removal, resulting in rapid concentration increases. Whereas previous studies classified gabapentin as not readily biodegradable, sustained removal was observed after prolonged operation and points at biological elimination of gabapentin within the GAC filter. The application of GAC as filter medium was compared to direct addition of powdered activated carbon (PAC) to deep-bed filtration as a direct process alternative. Both options yielded comparable OMP removals for most compounds at similar carbon usage rates, but GAC achieved considerably higher removals for biodegradable OMPs. Based on the results, the application of GAC in combination with coagulation/filtration represents a promising alternative to powdered activated carbon and ozone for advanced wastewater treatment.