The separation of affinity flocculated yeast cell debris using a pilot-plant scroll decanter centrifuge

The use of a scroll decanter centrifuge for the removal and dewatering of affinity-flocculated yeast cell debris from a crude homogenate is described. Laboratory shear modulus measurements were used to compare the structure of flocculated and nonflocculated sediments and to indicate the dewatering conditions under which the sediment could be discharged from the centrifuge. The structure of the flocculated sediment was such that a dry beach could be used within the centrifuge while still being able to discharge the solids. The scroll decanter performance for recovery and dewatering of the flocculated homogenate was found to be independent of feed flow rate and differential scroll rate. Eighty-five percent of the solid material was recovered from the flocculated homogenate while the extent of sediment dewatering resulted in the loss of only 7% of the soluble protein in the sediment. The supernatant clarity matched that achieved by low-gravity laboratory centrifugation studies.     

Isolation of indigenous enteroviruses from chemically treated and dewatered sludge samples.

Samples of wastewater sludge were examined for infectious enteroviruses before and after they had been chemically conditioned and dewatered. The least virus was recovered from the cake produced by filter pressing of sludge, which had a greatly increased solids content (39 to 45% [wt/vol]) relative to the untreated sludge (4.2 to 6.2% [wt/vol]) and in one plant was at pH 11 due to the lime conditioner used. Conditioning with a cationic polyelectrolyte before dewatering by centrifugation produced a watery sludge (2.7 to 5.3% [wt/vol]) from which high titers of infectious virus were recovered which were often greater than those isolated from the untreated sludge (0.6 to 1.4% [wt/vol]). This was thought to be due to saturation of virus and sludge floc adsorption sites by the polyelectrolyte, resulting in the liberation of virions from the sludge solids.     

Isolation of indigenous enteroviruses from chemically treated and dewatered sludge samples

Samples of wastewater sludge were examined for infectious enteroviruses before and after they had been chemically conditioned and dewatered. The least virus was recovered from the cake produced by filter pressing of sludge, which had a greatly increased solids content (39 to 45% [wt/vol]) relative to the untreated sludge (4.2 to 6.2% [wt/vol]) and in one plant was at pH 11 due to the lime conditioner used. Conditioning with a cationic polyelectrolyte before dewatering by centrifugation produced a watery sludge (2.7 to 5.3% [wt/vol]) from which high titers of infectious virus were recovered which were often greater than those isolated from the untreated sludge (0.6 to 1.4% [wt/vol]). This was thought to be due to saturation of virus and sludge floc adsorption sites by the polyelectrolyte, resulting in the liberation of virions from the sludge solids.     

Olive orchard amended with two experimental olive mill wastes mixtures: effects on soil organic carbon, plant growth and yield

Amendments of olive orchard soil with two different preparations of olive mill solid waste (OMWMs) at the rate of 9tonha(-1) per year for five years in two different plots were compared with an industry standard soil amendment using urea. Both the OMWMs amendments showed significant increases in total organic carbon and humic substances in soil of approximately 40% and 58%, respectively, without negative effects on tree growth and yield. This work has shown that olive oil mill waste (OMW) can be recycled safely using the bioremediation system used in this study. We suggest that this system is particularly beneficial to organic farming and is an alternative solution to direct spreading of raw OMW on farm lands.     

Super blue box recycling (SUBBOR) enhanced two-stage anaerobic digestion process for recycling municipal solid waste: laboratory pilot studies

The super blue box recycling (SUBBOR) process is an enhanced, multi-stage anaerobic digestion process for mixed municipal solid waste (MSW) and other biomass feedstock materials. The technology centers on enhanced high solids, thermophilic digestion after steam-pressure disruption of the ligno-cellulosic fiber components that are recalcitrant to conventional anaerobic digestion. Mixed MSW, rich in organic components but also containing inorganic materials, such as glass, aluminum and steel, as well as non-digestible plastic materials, has been laboratory pilot tested with a fully integrated process train designed to treat and recycle all of the MSW components. Methane yields from the MSW were 0.36 m3 CH4/kg volatile solids (VS) representing a 40% increase over the yield obtained from conventional single stage digestion. The secondary digestion step after steam pressure disruption also provided a 40% improvement in total solids and VS reduction. The residual organic fraction following two-stage digestion was fine in texture and was recovered as a clean peat fraction with reduced contents of heavy metal and other fugitive non-digested contaminants. Mass and energy balance determinations indicated a high degree of MSW diversion from landfill disposal (>80%) was achievable by the SUBBOR process as well as substantial net electrical and thermal energy production. Continuous long-term trials of the SUBBOR process at 25,000 tonnes/year are underway.     

Research collaborations can improve the use of organic amendments for plant-parasitic nematode management

The concept of utilizing organic amendments to manage plant-parasitic nematodes is not new, but the widespread implementation of this management practice has still not been realized. The use of organic amendments for plant-parasitic nematode management is a complex process requiring an understanding of the transformation and generation of active compounds. As a result, research endeavors to understand and maximize the use of this management practice require a multidisciplinary approach which draws upon the expertise of nematologists, microbiologists, natural product chemists and soil scientists. Factors that require analysis and clarification include lethal concentration levels of organic amendments necessary to kill nematodes; chemical composition of incorporation material; fate and exposure potential to nematodes of compounds released into the soil; and the influence of environmental factors (i.e., temperature, microbial community, soil type) on the activity of organic amendments. Examples of research conducted in a collaborative manner with rye (Secale cereale) and a biosolid amendment demonstrate the power of multidisciplinary research. Only through collaborative research can consistent and reliable nematode suppression with organic amendments be achieved.     

Willow growth in response to nutrients and moisture on a clay landfill cap soil. I. Growth and biomass production

The growth and biomass production by willow (Salix viminalis L.) was studied in lysimeters containing Oxford clay landfill cap soil with different amendments, bulk densities and watering regimes. Three years from planting, stem biomass in well-watered plants was least (0.28 kg plant(-1)) with high bulk density soil (1480 kg m(-3)) and no nutritional amendment but was increased 10-fold (2.53 kg plant(-1)) by reducing soil bulk density (1200 kg m3) and adding amendments. In comparison, on a sandy loam soil it was 6.23 kg plant(-1). There were similar differences in number of stems plant(-1), stem basal area plant(-1) and plant leaf area which can be attributed to low nitrogen and phosphorus levels in Oxford clay. Water stress reduced stem biomass production by 26-37% and caused higher root:stem ratios. These were also higher on Oxford clay than on the sandy loam. Successful biomass production from willow on Oxford clay landfill caps will therefore require nutritional amendment.     

Hydrodynamic studies in an airlift reactor with an enlarged degassing zone

The hydrodynamic behaviour of a 60?l three-phase airlift bioreactor, of the concentric draught tube type, with an enlarged degassing zone has been studied. Ca-alginate beads were used as the solid phase. Airflow rate (from 1.9 to 90.2?l/min), solids loading (0% to 40% (v/v)) and solids density (1016 and 1038?kg/m³) were manipulated and their influence on solids and gas holdup, circulation and mixing times and in the interstitial liquid velocity was determined. Riser and downcomer solids holdup was found to decrease with the increase of airflow rate and to increase with solids loading and density. On the contrary, gas holdup in the riser and in the downcomer increased with airflow rate and decreased with solids loading and density. By increasing airflow rate, a decrease in circulation time was observed while the effects of solids loading and density were negligible. Mixing time decreased with airflow rate, increased with solids density, in the studied range, and presented a maximum for solids loading of approximately 20% (v/v).     

Dewatering of contaminated sediments: Greenhouse and field studies

Water management of dredged sediments in Confined Disposal Facilities (CDFs) is an issue for the United States Army Corps of Engineers (USACE). Removing water from contaminated dredged sediments in CDFs is desirable because water removal can reduce the volume occupied by the sediments and can create the aerobic conditions needed for the microbial degradation of many contaminants found in the sediments. The objective of the current study was to identify plant species that could be used to dewater saturated sediments contaminated with PCBs and PAHs. A greenhouse study revealed that wetland plants (54–67% water removed) were able to dewater contaminated sediments more than unvegetated (28% water loss) or treatments with terrestrial plant treatments (39% water removed). Three promising species (Scirpus fluviatilis, Spartina pectinata, and Carex aquatalis) from the greenhouse study were tested in the field. In the field trials, wetland plants again were able to dewater sediments effectively. Some of the same species selected in the greenhouse study were the best dewatering species in the field study (S. fluviatilis and S. pectinata); however, the S. fluviatilis dewatered the sediments past its own permanent wilting point (0.323 g water/g soil). By the end of the final growing season, the Salix nigra (0.161 g water/g soil) and S. pectinata (18.4 g water/g soil) were able to dewater the sediments without negative impacts on the plants and are recommended for dewatering applications.     

Life-Cycle Assessment of Biosolids Processing Options

Biosolids, also known as sewage sludge, are reusable organic materials separated from sewage during treatment. They can be managed in a variety of ways. Different options for biosolids handling in Sydney, Australia, are compared in this study using life-cycle assessment. Two key comparisons are made: of system scenarios (scenario 1 is local dewatering and lime amendment; scenario 2 is a centralized drying system) and of technologies (thermal drying versus lime amendment). The environmental issues addressed are energy consumption, global warming potential (GWP), and human toxicity potential (HTP).
Scenario 2 would consume 24% more energy than scenario 1. This is due to the additional electricity for pumping and particularly the petrochemical methane that supplements biogas in the drier. A centralized system using the same technologies as scenario 1 has approximately the same impacts. The GWP and HTP of the different scenarios do not differ significantly.
The assessment of technology choices shows significant differences. The ample supply of endogenous biogas at North Head sewage treatment plant for the drying option allows reductions, relative to the lime-amendment option, of 68% in energy consumption, 45% in GWP, and 23% in HTP.
Technology choices have more significant influence on the environmental profile of biosolids processing than does the choice of system configurations. Controlling variables for environmental improvement are the selection of biogas fuel, avoidance of coalsourced electrical energy, minimization of trucking distances, and raising the solids content of biosolids products.     

Numerical modelling of vertical suspended solids concentrations and irradiance in a turbid shallow system (Vaccares,Se France)

In shallow ecosystems, the short temporal variability of available underwater irradiance is considered a major process controlling submerged macrophytes development. Mechanistic models that estimate photosynthetically available radiation (PAR) in shallow ecosystems at very short time scales are needed for use in predicting submerged macrophyte growth and persistence. We coupled a 2D horizontal circulation model with, first, a 1D vertical numerical model of suspended solid (SS) re-suspension, diffusion and settling, and next, with a model of vertical extinction of irradiance, previously validated at the same site. The study site was the Vaccarès lagoon (France) where a large data set of high frequency bottom irradiance and SS concentration were available. SS and irradiance measurements were conducted at a vertical study station, monitored over a 6 month period (from December 1995 to May 1996) characterized by wide-ranging wind velocities (1.5–18 ms⁻¹). In addition, grain-size analyses conducted over the whole lagoon, allowed adaptation of the 1D numerical model to the silt-sized (7 μm) and clay-sized (0.3 μm) fractions that prevail in the local sediment. First, model results showed that about 60% of the variance in bottom irradiance time series can be explained by our deterministic formulations, thus representing the same level of efficiency than those already obtained by a stochastic model previously developed with the same data set. Second, model results showed that the fit of the model to the field data (SS concentrations and bottom irradiance) depended mainly on storm occurrence and season (winter or spring). Finally, model results suggested that the underwater irradiance regime was controlled by seasonal succession of the horizontal circulation of turbid water in the lagoon, with increased solids concentrations in winter, followed by submerged canopy development and decreased solids concentrations in spring.     

Breakdown of low-level total petroleum hydrocarbons (TPH) in contaminated soil using grasses and willows

A phytoremediation study targeting low-level total petroleum hydrocarbons (TPH) was conducted using cool- and warm-season grasses and willows (Salix species) grown in pots filled with contaminated sandy soil from the New Haven Rail Yard, CT. Efficiencies of the TPH degradation were assessed in a 90-day experiment using 20–8.7–16.6 N-P-K water-soluble fertilizer and fertilizer with molasses amendments to enhance phytoremediation. Plant biomass, TPH concentrations, and indigenous microbes quantified with colony-forming units (CFU), were assessed at the end of the study. Switchgrass grown with soil amendments produced the highest aboveground biomass. Bacterial CFU's were in orders of magnitude significantly higher in willows with soil amendments compared to vegetated treatments with no amendments. The greatest reduction in TPH occurred in all vegetated treatments with fertilizer (66–75%) and fertilizer/molasses (65–74%), followed sequentially by vegetated treatments without amendments, unvegetated treatments with amendments, and unvegetated treatments with no amendment. Phytoremediation of low-level TPH contamination was most efficient where fertilization was in combination with plant species. The same level of remediation was achievable through the addition of grasses and/or willow combinations without amendment, or by fertilization of sandy soil.     

The Effect of Chemical Amendments Used for Phosphorus Abatement on Greenhouse Gas and Ammonia Emissions from Dairy Cattle Slurry: Synergies and Pollution Swapping

Land application of cattle slurry can result in incidental and chronic phosphorus (P) loss to waterbodies, leading to eutrophication. Chemical amendment of slurry has been proposed as a management practice, allowing slurry nutrients to remain available to plants whilst mitigating P losses in runoff. The effectiveness of amendments is well understood but their impacts on other loss pathways (so-called ‘pollution swapping’ potential) and therefore the feasibility of using such amendments has not been examined to date. The aim of this laboratory scale study was to determine how the chemical amendment of slurry affects losses of NH₃, CH₄, N₂O, and CO₂. Alum, FeCl₂, Polyaluminium chloride (PAC)- and biochar reduced NH₃ emissions by 92, 54, 65 and 77% compared to the slurry control, while lime increased emissions by 114%. Cumulative N₂O emissions of cattle slurry increased when amended with alum and FeCl₂ by 202% and 154% compared to the slurry only treatment. Lime, PAC and biochar resulted in a reduction of 44, 29 and 63% in cumulative N₂O loss compared to the slurry only treatment. Addition of amendments to slurry did not significantly affect soil CO₂ release during the study while CH₄ emissions followed a similar trend for all of the amended slurries applied, with an initial increase in losses followed by a rapid decrease for the duration of the study. All of the amendments examined reduced the initial peak in CH₄ emissions compared to the slurry only treatment. There was no significant effect of slurry amendments on global warming potential (GWP) caused by slurry land application, with the exception of biochar. After considering pollution swapping in conjunction with amendment effectiveness, the amendments recommended for further field study are PAC, alum and lime. This study has also shown that biochar has potential to reduce GHG losses arising from slurry application.     

Slash Pile Burning Effects on Soil Biotic and Chemical Properties and Plant Establishment: Recommendations for Amelioration

Ponderosa pine forest restoration consists of thinning trees and reintroducing prescribed fire to reduce unnaturally high tree densities and fuel loads to restore ecosystem structure and function. A current issue in ponderosa pine restoration is what to do with the large quantity of slash that is created from thinning dense forest stands. Slash piling burning is currently the preferred method of slash removal because it allows land managers to burn large quantities of slash in a more controlled environment in comparison with broadcast burning slash. However burning slash piles is known to have adverse effects such as soil sterilization and exotic species establishment. This study investigated the effects of slash pile burning on soil biotic and chemical variables and early herbaceous succession on burned slash pile areas. Slash piles were created following tree thinning in two adjacent approximately 20‐ha ponderosa pine (Pinus ponderosa) restoration treatments in the Coconino National Forest near Flagstaff, Arizona. We selected 30 burned slash pile areas and sampled across a gradient of the burned piles for arbuscular mycorrhizal (AM) propagule densities, the soil seed bank, and soil chemical properties. In addition, we established five 1‐m² plots in each burned pile to quantify the effect of living soil (AM inoculum) and seeding amendments on early herbaceous succession in burned slash pile areas. The five treatments consisted of a control (no treatment), living soil (AM inoculum) amendment, sterilized soil (no AM inoculum) amendment, seed amendment, and a seed/soil (AM inoculum) amendment. Slash pile burning nearly eliminated populations of viable seeds and AM propagules and altered soil chemical properties. Amending scars with native seeds increased the cover of native forbs and grasses. Furthermore adding both seed and living soil more than doubled total native plant cover and decreased ruderal and exotic plant cover. These results indicate that seed/soil amendments that increase native forbs and grasses may enhance the rate of succession in burned slash pile areas by allowing these species to outcompete exotic and ruderal species also establishing at the site through natural regeneration.     

Solids,organic load and nutrient concentration reductions in swine waste slurry using a polyacrylamide (PAM)-aided solids flocculation treatment

Increased swine production results in concentration of wastes generated within a limited geographical area, which may lead to land application rates exceeding the local or regional assimilatory capacity. This may result in pollutant transfer through surface water or soil-groundwater systems, environmental degradation, and/or odor concerns. Existing swine waste pit storage and lagoon treatment technologies may be inadequate to store or treat waste prior to land application without these concerns resulting. Efficient swine waste solids separation may reduce environmental health concerns and generate a value-added bioresource (solids). This study evaluated the efficiency of a polyacrylamide (PAM) flocculant-aided solids separation treatment to reduce pollution indicator concentrations in raw (untreated) swine waste slurry. Swine waste slurry solids separation efficiency through gravity settling (sedimentation) was evaluated before and after the addition of a proprietary polymeric (PAM) flocculant. Results indicated that polymer amendments at concentrations of 62.5-750 mg/l improved slurry solids separation efficiency and significantly reduced concentrations of other associated aquatic pollution indicators in a majority of analyses conducted (33 of 50 total analyses conducted). Results also suggested that PAM-aided solids separation from swine waste slurry might facilitate further treatment and/or disposal and therefore reduce associated environmental degradation potential.     

Production and oxidation of methane in a boreal mire after a decade of increased temperature and nitrogen and sulfur deposition

Natural wetlands are the single largest source of atmospheric methane (CH₄). Both a changed climate and deposition of anthropogenic nitrogen and sulfur can alter the production and oxidation of CH₄ respectively and thereby also CH₄ exchange. We used a long‐term (12 years) factorial field experiment in a boreal oligotrophic mire to evaluate the effects of greenhouse cover and addition of ammonium nitrate and sodium sulfate on the production and oxidation of CH₄ by applying laboratory incubations of samples from five depths in the mire. The rates of CH₄ production were measured without amendments and after the addition of either glucose or sulfate. Twelve years of increased nitrogen deposition has changed the mire from a Sphagnum‐dominated plant community to one dominated by sedges and dwarf shrubs. The deposition of nitrogen to the field plots caused increased production of CH₄ in incubations without amendments (34%), and also after amendments with glucose (40%) or sulfate (42%). This indicates increased substrate availability (without amendments) but also a greater abundance of methanogens (glucose amendment). The greenhouse cover caused a decrease in CH₄ production in incubations without amendments (34%), after glucose amendment (20%) and after sulfate amendment (31%). These responses indicate decreased substrate availability (without amendment) accompanied by the reduced abundance of methanogens (glucose amendment). The field application of sulfur had no effect on CH₄ production at the depth where maximal CH₄ production occurred. Closer to the mire surface, however, the rate of CH₄ production was significantly reduced by 32–45%. These results suggest that the deposition of sulfate has altered the vertical distribution of methanogens and sulfate‐reducing bacteria. The oxidation of CH₄ was not significantly affected by any of the long‐term field treatments.     

Weed seed bank response to 12 years of different fertilization systems

Fertilizer amendments can impact weed populations in a variety of ways. This study evaluated the effects of 12 year-long applications of different fertilization systems on size and composition of the weed seed bank in a conventionally managed maize monoculture field. Fertilization systems included all factorial combinations of two dairy cattle slurry rates, three vegetable, fruit and garden waste (VFG) compost rates, and three synthetic N fertilizer rates. Soil samples were taken in each subplot in May 2008 after sowing and prior to herbicide application. Residues recovered from soil samples were tested for weed seedling emergence to characterize soil seed banks. Total weed seed bank density was affected by mineral N fertilization but not by compost or animal slurry application. Weed seed bank composition was related to compost amendment and mineral N fertilization. Annual compost amendments reduced seed bank density of some persistent species (e.g., Chenopodium album and Solanum nigrum) irrespective of mineral N fertilization. Compost is a promising tool for incorporation into integrated weed control strategies aimed at reducing weed seed bank persistence.     

乙醇预处理麦秆的酶解性能研究简

采用H2 SO4催化和自催化乙醇法对麦秆进行预处理,比较预处理后麦秆的主要化学组成、纤维素酶解性能和半同步糖化发酵生产乙醇特性,并进行物料衡算。结果表明：H2 SO4催化和自催化乙醇预处理过程中纤维素固体回收率大于90％。添加非离子表面活性剂吐温20和吐温80没有显著提高H2 SO4催化乙醇预处理后纤维素的酶解葡萄糖得率及半同步糖化发酵过程中乙醇的产量,而对自催化乙醇处理后麦秆的酶解和半同步糖化发酵过程有一定程度的促进作用,相应的酶解葡聚糖转化率由72.7％提高到85.0％,而半同步糖化发酵过程中乙醇质量浓度提高了11.4％。物料衡算结果表明：酸催化和自催化乙醇预处理后葡聚糖回收率分别为91.0％和95.4％;半同步糖化发酵生产乙醇的得率分别为10.4和11.6 g（按100 g原料计）。     

Microbial pretreatment of cotton stalks by solid state cultivation of Phanerochaete chrysosporium

White rot fungi degrade lignin and have biotechnological applications in conversion of lignocellulose to valuable products. Pretreatment is an important processing step to increase the accessibility of cellulosic material in plant biomass, impacting efficiency of subsequent hydrolysis and fermentation. This study investigated microbial pretreatment of cotton stalks by solid state cultivation (SSC) using Phanerochaete chrysosporium to facilitate the conversion into ethanol. The effects of substrate moisture content (M.C.; 65%, 75% and 80% wet-basis), inorganic salt concentration (no salts, modified salts without Mn(2+), modified salts with Mn(2+)) and culture time (0-14 days) on lignin degradation (LD), solids recovery (SR) and availability of carbohydrates (AOC) were examined. Moisture content significantly affected lignin degradation, with 75% and 80% M.C. degrading approximately 6% more lignin than 65% M.C. after 14 days. Within the same moisture content, treatments supplemented with salts were not statistically different than those without salts for LD and AOC. Within the 14day pretreatment, additional time resulted in greater lignin degradation, but indicated a decrease in SR and AOC. Considering cost, solid state cultivation at 75% M.C. without salts was the most preferable pretreatment resulting in 27.6% lignin degradation, 71.1% solids recovery and 41.6% availability of carbohydrates over a period of 14 days. Microbial pretreatment by solid state cultivation has the potential to be a low cost, environmentally friendly alternative to chemical approaches. Moisture relationships will be significant to the design of an effective microbial pretreatment process using SSC technology.     

Effect of organic amendments on some physical, chemical and biological properties in a horticultural soil

The aim of the present work was to assess the response of selected soil physical, chemical and biological properties, after two applications of different organic amendments to a soil with an extended horticultural use. Vermicompost from household solid waste (HSW) and from horse and rabbit manure (HRM), and chicken manure (CM) were applied at rates of 10 and 20 Mg ha(-1). The proportion of water stable soil aggregates (Ws) was significantly higher (p < 0.05) in HSW, HRM and CM at 20 Mg ha(-1). The proportion of ethanol stable soil aggregates (Es) was significantly higher in HSW, HRM and CM at 20 Mg ha(-1), and CM at 10 Mg ha(-1). After the first amendment application, HSW and HRM at 20 Mg ha(-1) resulted in higher soil organic carbon (SOC), while all the treatments showed a significant increase after the second amendment application. Linear relationships were found between Ws and Es with SOC. An increment in microbial respiration in all the amended plots was observed with the exception of HRM at the rate of 10 Mg ha(-1).