Composition and variability of biofouling organisms in seawater reverse osmosis desalination plants

Seawater reverse osmosis (SWRO) membrane biofouling remains a common challenge in the desalination industry, but the marine bacterial community that causes membrane fouling is poorly understood. Microbial communities at different stages of treatment processes (intake, cartridge filtration, and SWRO) of a desalination pilot plant were examined by both culture-based and culture-independent approaches. Bacterial isolates were identified to match the genera Shewanella, Alteromonas, Vibrio, and Cellulophaga based on 16S rRNA gene sequencing analysis. The 16S rRNA gene clone library of the SWRO membrane biofilm showed that a filamentous bacterium, Leucothrix mucor, which belongs to the gammaproteobacteria, accounted for nearly 30% of the clone library, while the rest of the microorganisms (61.2% of the total clones) were related to the alphaproteobacteria. 16S rRNA gene terminal restriction fragment length polymorphism (T-RFLP) analysis indicated that bacteria colonizing the SWRO membrane represented a subportion of microbes in the source seawater; however, they were quite different from those colonizing the cartridge filter. The examination of five SWRO membranes from desalination plants located in different parts of the world showed that although the bacterial communities from the membranes were not identical to each other, some dominant bacteria were commonly observed. In contrast, bacterial communities in source seawater were significantly different based on location and season. Microbial profiles from 14 cartridge filters collected from different plants also revealed spatial trends.     

Dynamic bacterial communities on reverse-osmosis membranes in a full-scale desalination plant

To better understand biofouling of seawater reverse osmosis (SWRO) membranes, bacterial diversity was characterized in the intake water, in subsequently pretreated water and on SWRO membranes from a full-scale desalination plant (FSDP) during a 9 month period. 16S rRNA gene fingerprinting and sequencing revealed that bacterial communities in the water samples and on the SWRO membranes were very different. For the different sampling dates, the bacterial diversity of the active and the total bacterial fractions of the water samples remained relatively stable over the sampling period whereas the bacterial community structure on the four SWRO membrane samples was significantly different. The richness and evenness of the SWRO membrane bacterial communities increased with usage time with an increase in the Shannon diversity index of 2.2 to 3.7. In the oldest SWRO membrane (330 days), no single operational taxonomic unit (OTU) dominated and the majority of the OTUs fell into the Alphaproteobacteria or the Planctomycetes. In striking contrast, a Betaproteobacteria OTU affiliated to the genus Ideonella was dominant and exclusively found in the membrane used for the shortest time (10 days). This suggests that bacteria belonging to this genus could be one of the primary colonizers of the SWRO membrane. Knowledge of the dominant bacterial species on SWRO membranes and their dynamics should help guide culture studies for physiological characterization of biofilm forming species.     

Alternatives for Reducing the Environmental Impact of the Main Residue From a Desalination Plant

One of the most important problems today is the scarcity of fresh water safe enough for human, industrial, and agricultural use. Desalination is an alternative source of fresh water supply in areas with severe problems of water availability. Desalination plants generate a huge amount of brine as the main residual from the plant (about 55% of collected seawater). Because of that, it is important to determine the best environmental option for the brine disposal. This article makes a global environmental analysis, under Spanish conditions, of a desalination plant and an environmental assessment of different final brine disposals, representing a range of the most common alternatives: direct disposal, wastewater treatment plant (WWTP) outflow dilution, and dilution with seawater. The environmental profile of the plant operation and a comparison of the brine final disposal alternatives were established by means of the life cycle assessment (LCA) methodology. From an analysis of the whole plant we observed that the highest environmental impact was caused by energy consumption, especially at the reverse osmosis stage, while the most relevant waste was brine. From an analysis of brine final disposal we have elaborated a comparison of the advantages and detriments of the three alternatives. As all of them might be suitable in different specific situations, the results might be useful in decisions about final brine disposal.     

Fertiliser drawn forward osmosis desalination: the concept, performance and limitations for fertigation

With the world??s population growing rapidly, pressure is increasing on the limited fresh water resources. Membrane technology could play a vital role in solving the water scarcity issues through alternative sources such as saline water sources and wastewater reclamation. The current generation of membrane technologies, particularly reverse osmosis (RO), has significantly improved in performance. However, RO desalination is still energy intensive and any effort to improve energy efficiency increases total cost of the product water. Since energy, environment and climate change issues are all inter-related, desalination for large-scale irrigation requires new novel technologies that address the energy issues. Forward osmosis (FO) is an emerging membrane technology. However, FO desalination for potable water is still a challenge because, recovery and regeneration of draw solutes require additional processes and energy. This article focuses on the application of FO desalination for non-potable irrigation where maximum water is required. In this concept of fertiliser drawn FO (FDFO) desalination, fertilisers are used as draw solutions (DS). The diluted draw solution after desalination can be directly applied for fertigation without the need for recovery and regeneration of DS. FDFO desalination can make irrigation water available at comparatively lower energy than the current desalination technologies. As a low energy technology, FDFO can be easily powered by renewable energy sources and therefore suitable for inland and remote applications. This article outlines the concept of FDFO desalination and critically evaluates the scope and limitations of this technology for fertigation, including suggestions on options to overcome some of these limitations.     

Resource and energy recovery options for fermentation industry residuals

Over the last 40 years, the fermentation industry has provided facility planners, plant operators and environmental engineers with a wide range of residuals management challenges and resource/energy recovery opportunities. In response, the industry has helped pioneer the use of a number of innovative resource and energy recovery technologies. Production of animal feed supplements, composts, fertilizers, soil amendments, commercial baking additives and microbial protein materials have all been detailed in the literature. In many such cases, recovery of by-products significantly reduces the need for treatment and disposal facilities. Stable, reliable anaerobic biological treatment processes have also been developed to recovery significant amounts of energy in the form of methane gas. Alternatively, dewatered or condensed organic fermentation industry residuals have been used as fuels for incineration-based energy recovery systems. The sale or use of recovered by-products and/or energy can be used to offset required processing costs and provide a technically and environmentally viable alternative to traditional treatment and disposal strategies. This review examines resource recovery options currently used or proposed for fermentation industry residuals and the conditions necessary for their successful application.     

Phytoextraction of salts by Atriplex Nummularia Lindl. irrigated with reject brine under varying water availability

Abstract

Reverse osmosis is a widely known technology used to produce fresh water from brackish waters. However, the reject brine from desalination plants poses a serious threat to the environment due to soil and groundwater salinization. The aim of this study was to investigate the potential of Atriplex nummularia to extract salts from a soil irrigated with reverse osmosis brine, at varying moisture levels. A field experiment was conducted in a split-plot design, with randomized complete blocks replicated four times. Treatments consisted of irrigation with reject brine in the main plots, with four relative percentages of the soil moisture at field capacity (100, 85, 70, and 50%), and two levels of organic fertilization in the subplots (0 and 1.5?L plant^?1 of goat manure). The mineral composition of leaves and stems indicated that the highest salt extraction by plants occurred when soil moisture was maintained at 100% field capacity. The salt extraction capacity of A. nummularia indicates a high potential for phytoremediation of soils affected by brine disposal from reverse osmosis plants.     

Life Cycle Assessment of Water Production Technologies - Part 1: Life Cycle Assessment of Different Commercial Desalination Technologies (MSF,MED, RO) (9 pp)

- Preamble. This series of two papers analyses and compares the environmental loads of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment with the present state of the art of the technology. Further, it is also presented an estimation of the potential environmental loads that the considered technologies could provoke in future, taking into account the most suitable evolution of the technology. - Part 1 presents the assessment of most commercial desalination technologies which are spread worldwide: Reverse Osmosis, Multi Effect Desalination and Multi Stage Flash. Part 2 presents the comparative LCA analysis of a big hydraulic infrastructure, as is to be found in the Ebro River Water Transfer project, with respect to desalination. - DOI: http://dx.doi.org/10.1065/lca2004.09.179.1 - Intention, Goal and Background. In this paper, some relevant results of a research work are presented, the main aim of which consists of performing the environmental assessment of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment of potable water supply to the end users. That is, the scope of this paper is mostly oriented to the comparative Life Cycle Assessment of different water production technologies instead of presenting new advancements in the LCA methodology. In Part 1, the environmental loads associated with the most widespread and important commercial desalination technologies all over the world - Reverse Osmosis (RO), Multi Effect Desalination (MED) and Multi Stage Flash (MSF) – are compared. The assessment technique is the Life Cycle Analysis (LCA), which includes the entire life cycle of each technology, encompassing: extraction and processing raw materials, manufacturing, transportation and distribution, operation and final waste disposal.- Methods and Main Features. The software SimaPro 5.0, developed by Dutch PRé Consultants, has been used as the analysis tool, because it is a well known, internationally accepted and validated tool. Different evaluation methods have been applied in the LCA evaluation: CML 2 baseline 2000, Eco-Points 97 and Eco-Indicator 99. Data used in the inventory analysis of this Part 1 come from: a) existing plants in operation; b) data bases implemented in the SimaPro 5.0 software -BUWAL 250, ETH-ESU 96, IDEMAT 2001. Different scenarios have been analyzed in both parts in order to estimate, not only the potential of reduction of the provoked environmental loads with the present state of the art of technology, but also the most likely future trend of technological evolution. In Part 1, different energy production models and the integration of desalination with other productive processes are studied, while the effect of the most likely technological evolution in the midterm, and the estimation of the environmental loads to the water transfer during drought periods are considered in Part 2. Results and Discussion The main contribution to the global environmental impact of desalination technologies comes from the operation, while the other phases, construction and disposal, are almost negligible when compared to it. Energy is very important in desalination, for this reason the environmental loads change a lot depending on the technology used for providing the energy used in the desalination process. Among the different analyzed technologies, RO is the least aggressive desalination technology (one order of magnitude lower than the thermal processes, MSF and MED) for the environment. When integrating thermal desalination with other productive processes taking advantage of the residual heat, the environmental loads of thermal desalination technologies is highly reduced, obtaining similar loads to that of RO. The environmental loads of desalination technologies are significantly reduced when an energy model based on renewable energies is used. Taking into account the technological evolution, which is experiencing the RO, a reduction of its environmental load by about 40% is to be expected in the mid-term. Conclusion The main conclusion of Part 1 is that, with the present state of the art of the technology, RO is clearly the desalination technology with a reduced environmental load (one order of magnitude lower than the thermal processes, MSF and MED). In the case of thermal desalination technologies, their environmental load can be highly reduced (about 1,000 times less) when integrated with other industrial processes. In the case of RO, the scores and the airborne emissions obtained from an electricity production model based on renewable energies are about 65-70 times lower than those obtained when the electricity production model is mainly based on fossil fuels. Recommendations and Outlook Although desalination technologies are energy intensive and provoke an important environmental load, they present a high potential in being reduced since: a) in the mid-term, it is to be expected that the different technologies could improve their efficiency significantly, b) the environmental loads would be highly reduced if the energy production models were not mainly based on fossil fuels and c) the energy consumption, particularly in the case of thermal desalination, can be drastically reduced when integrating desalination with other productive processes. The results presented in this paper indicate that a very interesting and promising field of research is available in order to reduce the environmental load of these vigorous and increasing desalination technologies.     

Life Cycle Assessment of Water Production Technologies - Part 2: Reverse Osmosis Desalination versus the Ebro River Water Transfer (9 pp)

- Preamble. This series of two papers analyses and compares the environmental loads of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment with the present state of the art of technology. Further, an estimation of the potential environmental loads that the considered technologies could provoke in future is also presented, taking into account the most suitable evolution of the technology. - Part 1 presents the assessment of most commercial desalination technologies which are spread worldwide: Reverse Osmosis, Multi Effect Desalination and Multi Stage Flash. Part 2 presents the comparative LCA analysis of a big hydraulic infrastructure, as is to be found in the Ebro River Water Transfer project, with respect to desalination. - Intention, Goal and Background. In this paper some relevant results of a research work are presented, the main aim of which consists of performing the environmental assessment of different water production technologies in order to establish, in a global, rigorous and objective way, the less aggressive technology for the environment for supplying potable water to the end users. The scope of this paper is mostly oriented to the comparative Life Cycle Assessment of different water production technologies instead of presenting new advancements in the LCA methodology. Based on the results obtained in Part 1 (LCA of most widespread commercial desalination technologies), the particular case of a big hydraulic project, which is the Ebro River Water Transfer (ERWT) considered in the Spanish National Hydrologic Plan, versus the production by desalination of the same amount of water to be diverted, is compared in Part 2. The assessment technique is the Life Cycle Analysis (LCA), which includes the entire life cycle of each technology, encompassing: extraction and processing raw materials, manufacturing, transportation and distribution, operation and final waste disposal. Methods and Main Features. The software SimaPro 5.0, developed by Dutch PRé Consultants, has been used as the analysis tool, because it is a well known, internationally accepted and validated tool. Different evaluation methods have been applied in the LCA evaluation: CML 2 baseline 2000, Eco-Points 97 and Eco-Indicator 99. Data used in the inventory analysis of this Part 2 come from: a) desalination: data obtained for existing plants in operation; b) ERWT: Project approved in the Spanish National Hydrologic Plan and its Environmental Impact Evaluation and; c) data bases implemented in the SimaPro software – BUWAL 250, ETH-ESU 96, IDEMAT 2001. Different scenarios have been analyzed in both parts in order to estimate not only the potential of reduction of the provoked environmental loads with the present state of the art of technology, but also the most likely future trend of technological evolution. In Part 1, different energy production models and the integration of desalination with other productive processes are studied, while the effect of the most likely technological evolution in the midterm, and the estimation of the environmental loads to the water transfer during drought periods are considered in Part 2. Results and Discussion As proven in Part 1, RO is a less aggressive desalination technology for the environment. Its aggression is one order of magnitude lower than that of the thermal processes, MSF and MED. The main contribution to the global environmental impact of RO comes from the operation, while the other phases, construction and disposal, are almost negligible when compared to it. In the case of the ERWT, the contribution of the operation phase is also the most important one, but the construction phase has an important contribution too. Its corresponding environmental load, with the present state of the art of technology, is slightly lower than that provoked by the RO desalination technology. However, the results obtained in the different scenarios analyzed show that the potential reduction of the environmental load in the case of the ERWT is significantly lower than that in the case of the RO. The effect of drought periods in the assessed environmental loads of the water transfer is not negligible, obtaining as a result an increasing environmental load per m3 of diverted water. Conclusion The environmental load associated with RO, with the present state of the art of technology, is slightly higher than that provoked by the ERWT. However, considering the actual trend of technological improvement of the RO and the present trend of energy production technology in the address of reducing the fossil fuels\ contribution in the electricity production, the environmental load associated with RO in the short mid-term would be likely to be lower than that corresponding to the ERWT. Recommendations and Outlook Although desalination technologies are energy intensive and provoke an important environmental load, as already explained in Part 1, they present a high potential of reducing it. In respect to ERWT, the results indicate, when the infrastructure of ERWT is completed (by 2010–2012), that the LCA of RO will be likely to be against the water transfer. With the present technological evolution of water production technologies and from the results obtained in this paper, it seems, from an environmental viewpoint, that big hydraulic projects should be considered the last option because they are rigid and long-term infrastructures (several decades and even centuries of operation) that provoke important environmental loads with only a small margin for reducing them.     

Review on modelling and control of desalination system using reverse osmosis

Dissolved salts in seawater or brackish water are reduced to a potable level through separation techniques, like, distillation, multiple effect vapor compression, evaporation, or by membrane processes such as electro-dialysis reversal, nano-filtration, and reverse osmosis (RO). RO is the most widely used desalination process. Recent advances in RO technology has led to more efficient separation and now is the most cost effective process to operate. The performance of the reverse osmosis process is dependent on concentration of dissolved solids in the feed-water, feed-water pressure, and the membrane strength to withstand system pressure, membrane solute rejection, membrane fouling characteristics, and the required permeate solute concentration. RO is a promising tool that uses cellulose acetate (or) polyamide membrane and is widely chosen as the cost of production is reduced by the use of energy efficient and process control techniques. This paper presents a review on modelling, identification of parameters from single input-outputs and multi input/output lumped systems, dynamic modelling and control of desalination systems in the past twenty years by collecting more than 60 literatures.     

Process Simulation and Cost Analysis for Removing Inorganics from Wood Chips Using Combined Mechanical and Chemical Preprocessing

Inorganic species (ash) in biomass feedstocks negatively impact thermochemical and biochemical energy conversion processes. In this work, a process simulation model is developed to model the reduction in ash content of loblolly logging residues using a combination of air classification and dilute-acid leaching. Various scenarios are considered, and it is found that costs associated with discarding high-ash material from air classification are substantial. The costs of material loss can be reduced by chemical leaching the high-ash fraction obtained from air classification. The optimal leaching condition is found to be approximately 0.1 wt% sulfuric acid at 24 °C. In example scenarios, total process costs in the range of $6–9?/dry tons of product are projected that result in a removal of 14, 62, 39, and 88 % of organics, total ash (inorganics), alkaline earth metals and phosphorus (AAEMS + P), and silicon, respectively. Sensitivity analyses indicate that costs associated with loss of organic material during processing (yield losses), brine disposal, and labor have the greatest potential to impact the total processing cost.     

氨基酸废水处理技术的研究进展

氨基酸废水处理技术一直是国内外氨基酸生产厂家和环保界的研究热点。本文对国内外氨基酸废水处理方法,如膜分离法、生物法等进行了详细评述,认为生物法是解决我国氨基酸废水污染的最终出路,同时提出将三维电极电化学法应用于氨基酸废水的处理,具有重要的理论意义和实际的应用价值。     

Production of poly-3-(hydroxybutyrate-co-hydroxyvalerate) by Haloferax mediterranei using rice-based ethanol stillage with simultaneous recovery and re-use of medium salts

Haloferax mediterranei holds promise for competitive industrial-scale production of polyhydroxyalkanoate (PHA) because cheap carbon sources can be used thus lowering production costs. Although high salt concentration in production medium permits a non-sterile, low-cost process, salt disposal after process completion is a problem as current environmental standards do not allow total dissolved solids (TDS) above 2000 mg/l in discharge water. As the first objective of this work, the waste product of rice-based ethanol industry, stillage, was used for the production of PHA by H. mediterranei in shake flasks. Utilization of raw stillage led to 71 ± 2 % (of dry cell weight) PHA accumulation and 16.42 ± 0.02 g/l PHA production. The product yield coefficient was 0.35 while 0.17 g/l h volumetric productivity was attained. Simultaneous reduction of BOD₅ and COD values of stillage by 83 % was accomplished. The PHA was isolated by osmotic lysis of cells, purification by sodium dodecyl sulfate and organic solvents. The biopolymer was identified as poly-3-(hydroxybutyrate-co-15.4 mol%-hydroxyvalerate) (PHBV). This first report on utilization of rice-based ethanol stillage for PHBV production by H. mediterranei is currently the most cost effective. As the second objective, directional properties of decanoic acid together with temperature dependence of water solubility in decanoic acid were applied for two-stage desalination of the spent stillage medium. We report for the first time, recovery and re-use of 96 % of the medium salts for PHA production thus removing the major bottleneck in the potential application of H. mediterranei for industrial production of PHBV. Final discharge water had TDS content of 670 mg/l.     

Membrane science and technology: leader in water treatment industry

Filtration and separation can represent as much as 80?% of the operating costs for many industries, and membrane separations are gaining acceptance as a cost-effective option in many production settings. Newer, more efficient membrane separation techniques can lead to more streamlined production and produce significant improvements in quality (http://www.mastcenter.org/default.htm). It is exciting to note the significant growth of membrane activities in the world, particularly in the area of desalination and municipal water purification. This interest is documented also by the industrial realization in reverse osmosis units, ultrafiltration and membrane bio-reactor. Also at fundamental research level, various new institutes are focusing their attention on the development of membrane research projects. This web alert overviews some important websites sharing knowledge on membrane science and technology.     

A comprehensive review of microbial electrochemical systems as a platform technology

Microbial electrochemical systems (MESs) use microorganisms to covert the chemical energy stored in biodegradable materials to direct electric current and chemicals. Compared to traditional treatment-focused, energy-intensive environmental technologies, this emerging technology offers a new and transformative solution for integrated waste treatment and energy and resource recovery, because it offers a flexible platform for both oxidation and reduction reaction oriented processes. All MESs share one common principle in the anode chamber, in which biodegradable substrates, such as waste materials, are oxidized and generate electrical current. In contrast, a great variety of applications have been developed by utilizing this in situ current, such as direct power generation (microbial fuel cells, MFCs), chemical production (microbial electrolysis cells, MECs; microbial electrosynthesis, MES), or water desalination (microbial desalination cells, MDCs). Different from previous reviews that either focus on one function or a specific application aspect, this article provides a comprehensive and quantitative review of all the different functions or system constructions with different acronyms developed so far from the MES platform and summarizes nearly 50 corresponding systems to date. It also provides discussions on the future development of this promising yet early-stage technology.     

Direct Electrolytic Splitting of Seawater: Activity,Selectivity, Degradation,and Recovery Studied from the Molecular Catalyst Structure to the Electrolyzer Cell Level

Seawater electrolysis faces fundamental chemical challenges, such as the suppression of highly detrimental halogen chemistries, which has to be ensured by selective catalyst and suitable operating conditions. In the present study, nanostructured NiFe‐layered double hydroxide and Pt nanoparticles are selected as catalysts for the anode and cathode, respectively. The seawater electrolyzer is tested successfully for 100 h at maximum current densities of 200 mA cm^?2 at 1.6 V employing surrogate sea water and compared to fresh water feeds. Different membrane studies are carried out to reveal the cause of the current density drop. During long‐term dynamic tests, under simulated day‐night cycles, an unusual cell power performance recovery effect is uncovered, which is subsequently harnessed in a long‐term diurnal day‐night cycle test. The natural day‐night cycles of the electrolyzer input power can be conceived as a reversible catalyst materials recovery treatment of the device when using photovoltaic electricity sources. To understand the origin of this reversible recovery on a molecular materials level, in situ extended X‐ray absorption fine structure and X‐ray near‐edge region spectra are applied.     

Fouling in reverse osmosis (RO) membrane in water recovery from secondary effluent: a review

Reverse osmosis (RO) is the most preferable process for water recovery from secondary effluent (SE) because of its higher rejection of impurities with lower associated cost and higher quality of product. Fouling still is a major challenge during the water recovery due to higher contaminant loadings in SE and high rejection capability of this membrane. The presence of suspended solids, colloidal and organic matters, and high level of biological activities in SE further elevate fouling potentiality. This review was performed to identify major foulants causing hindrance in sustainable application of reverse osmosis and to present available pre-treatment options for these foulants. There are four fouling types present in RO namely; bio-fouling, inorganic/scaling, organic, and particulate fouling. Among them; bio-fouling is less understood but dominant since the pre-treatment options are not well developed. Other fouling mechanisms have been overcome by well developed pre-treatments. The major foulants for RO are dissolved and macromolecular organic substances, sparingly soluble inorganic compounds, colloidal and suspended particles, and micro-organisms. Some of these potential fouling water quality parameters (PFWQPs) are interrelated with each others such as electrical conductivity is a surrogate measure of total dissolved solids with established stable relationship. Most of these PFWQPs such as total suspended solids, turbidity, chemical oxygen demand can be removed by conventional pre-treatment; some such as colloidal particles and micro-organisms by modern options and even others such as endocrine disrupting compounds, pharmaceutical and personal care products are still challenging for current pre-treatments. These foulants need to be identified properly to integrate appropriate pre-treatments for minimizing fouling potentiality to increase water recovery at minimal costs.     

异养微生物在金属生物淋滤技术中的应用

生物淋滤技术主要应用于低品位矿石金属选矿、煤气脱硫、废弃物中金属回收和污染介质中金属离子毒性的去除等方面。作为生物淋滤技术中的主体微生物之一,异养微生物可通过其产生的酸性代谢物还原、酸化及络合,提取或者溶解非硫化矿、固体废弃物、污水污泥及土壤中的金属,有助于解决目前的资源短缺问题,还可对污染环境治理提供技术支持,具有重要的理论意义和实践价值。应用于异养微生物淋滤技术中的常见微生物包括细菌(以假单胞菌为主)和真菌(以曲霉菌和青霉菌应用最为广泛)。淋滤过程涉及酸解、络合、还原及碱化等。目前,异养微生物淋滤技术主要应用于生物冶金、固体废弃物处理、污水处理和污染土壤修复等。本文分析了异养微生物金属淋滤过程中的问题,并提出了未来研究的发展方向。     

Food and processing residues in California: resource assessment and potential for power generation

The California agricultural industry produces more than 350 commodities with a combined yearly value in excess of $28 billion. The processing of many of these crops results in the production of residue streams, and the food processing industry faces increasing regulatory pressure to reduce environmental impacts and provide for sustainable management and use. Surveys of food and other processing and waste management sectors combined with published state data yield a total resource in excess of 4 million metric tons of dry matter, with nearly half of this likely to be available for utilization. About two-thirds of the available resource is produced as high-moisture residues that could support 134 MWe of power generation by anaerobic digestion and other conversion techniques. The other third is generated as low-moisture materials, many of which are already employed as fuel in direct combustion biomass power plants. The cost of energy conversion remains high for biochemical systems, with tipping or disposal fees of the order of $30-50Mg(-1) required to align power costs with current market prices. Identifying ways to reduce capital and operating costs of energy conversion, extending operating seasons to increase capacity factors through centralizing facilities, combining resource streams, and monetizing environmental benefits remain important goals for restructuring food and processing waste management in the state.     

高活力5′-磷酸二酯酶制备及水解RNA的研究

目的:获得高活力5′-磷酸二酯酶液,提高核酸RNA酶解效率。方法:采用超滤和盐析技术对从麦芽根浸提液中纯化5′-磷酸二酯酶工艺进行研究,采用单因子试验法优化酶解工艺条件。结果:浸提液依次经过5万Da超滤膜浓缩、40%饱和度硫酸铵盐析、5万Da超滤膜脱盐后,酶活力可达1 500U/ml;第1次超滤膜透过液可作为浸提液循环使用,酶活力是水浸提的1.15倍;第2次超滤膜透过液浓缩5倍后,可回收56.46%硫酸铵,浓缩母液可按1∶2比例循环使用;在底物浓度5.8%、酶用量8%、反应时间2h条件下,RNA酶解率可达95%。结论:初步建立了适合工业化规模的核苷酸生产新工艺。     

Process and economic analysis of pretreatment technologies

Five pretreatment processes (dilute acid, hot water, ammonia fiber explosion (AFEX), ammonia recycle percolation (ARP), and lime) for the liberation of sugars from corn stover are compared on a consistent basis. Each pretreatment process model was embedded in a full bioethanol facility model so that systematic effects for variations in pretreatment were accounted in the overall process. Economic drivers influenced by pretreatment are yield of both five and six carbon sugars, solids concentration, enzyme loading and hemicellulase activity. All of the designs considered were projected to be capital intensive. Low cost pretreatment reactors in some pretreatment processes are often counterbalanced by higher costs associated with pretreatment catalyst recovery or higher costs for ethanol product recovery. The result is little differentiation between the projected economic performances of the pretreatment options. Additional process performance data, especially involving the identification of optimal enzyme blends for each pretreatment approach and conditioning requirements of hydrolyzates at process-relevant sugar concentrations resulting from each pretreatment may lead to greater differentiation in projected process economics.