The importance of source configuration in quantifying footprints of regional atmospheric sulphur deposition

An atmospheric transport-chemistry model is applied to investigate the effects of source configuration in simulating regional sulphur deposition footprints from elevated point sources. Dry and wet depositions of sulphur are calculated for each of the 69 largest point sources in the UK. Deposition contributions for each point source are calculated for 2003, as well as for a 2010 emissions scenario. The 2010 emissions scenario has been chosen to simulate the Gothenburg protocol emission scenario. Point source location is found to be a major driver of the dry/wet deposition ratio for each deposition footprint, with increased precipitation scavenging of SO_x in hill areas resulting in a larger fraction of the emitted sulphur being deposited within the UK for sources located near these areas. This reduces exported transboundary pollution, but, associated with the occurrence of sensitive soils in hill areas, increases the domestic threat of soil acidification. The simulation of plume rise using individual stack parameters for each point source demonstrates a high sensitivity of SO₂ surface concentration to effective source height. This emphasises the importance of using site-specific information for each major stack, which is rarely included in regional atmospheric pollution models, due to the difficulty in obtaining the required input data. The simulations quantify how the fraction of emitted SO_x exported from the UK increases with source magnitude, effective source height and easterly location. The modelled reduction in SO_x emissions, between 2003 and 2010 resulted in a smaller fraction being exported, with the result that the reductions in SO_x deposition to the UK are less than proportionate to the emission reduction. This non-linearity is associated with a relatively larger fraction of the SO₂ being converted to sulphate aerosol for the 2010 scenario, in the presence of ammonia. The effect results in less-than-proportional UK benefits of reducing in SO₂ emissions, together with greater-than-proportional benefits in reducing export of UK SO₂ emissions.     

Emissions of ammonia and nitrous oxide following incorporation into the soil of farmyard manures stored at different densities

Before spreading to land, farmyard manures (FYM) from pigs (Sus scrofa) and beef cattle (Bos taurus) were stored, for c. 120–150 days, either uncompacted or compacted. Compaction was carried out as the manures were put into store and the compacted manures were covered with plastic sheeting. Both compacted and uncompacted FYM were either incorporated by ploughing immediately after spreading, within 4 h, within 24 h or left on the surface until the soil was cultivated prior to planting. Despite greater amounts of total ammoniacal nitrogen (TAN) remaining in the compacted pig FYM, ammonia (NH₃) emissions following spreading were not significantly greater than from the uncompacted FYM, even when left on the soil surface. Incorporation of pig FYM reduced NH₃ emissions by c. 90, 60 and 30% for immediate, within 4 h and within 24 h incorporation, respectively. There were no effects of compaction during storage on nitrous oxide (N₂O) emissions following spreading for the measurement period of 60 days. Incorporation had no effect on N₂O emissions from pig FYM following spreading in the first experiment, but reduced emissions following spreading in the second year and reduced N₂O emissions following the spreading of cattle FYM in both experiments. These results indicate that rapid incorporation of FYM after spreading to land is an effective means of reducing NH₃ emissions and need not lead to increases in N₂O emissions.     

Performance of Grease Abatement Devices for Removal of Fat, Oil, and Grease

This study assessed the performance of a conventional grease abatement device and the impact of internal geometry modifications on fat, oil, and grease (FOG) removal efficiency. Analysis was performed using experimental results and computational fluid dynamics (CFD) on alternative inlet, outlet, and baffle wall designs. Numerical and experimental results indicated that the conventional two-compartment design leads to substantial FOG short circuiting when operated at a 20-min hydraulic retention time (HRT). Alterations to the inlet configuration and baffle wall arrangement yielded FOG removal enhancements with the 20-min HRT that approached removal performance levels obtained with the standard configurations at the 1-h HRT. CFD simulations effectively reproduced performance trends observed on the lab-scale with the exception of simulations using a distributive inlet tee, where CFD over predicted the removal performance.     

Development and Evaluation of a Copolymer for Removal of Taste and Odor Causing Compounds from Lake Michigan Water

In this study, a copolymer, cyclodextrin/epichlorohydrin was synthesized and used as an adsorbent to remove two taste and odor causing compounds, namely, MIB and geosmin from the Lake Michigan water. The removal efficiency of these compounds using the copolymer on average was 74.5% for MIB and 77.5% for geosmin as compared to the removal efficiency using powdered activated carbon that resulted in 52.9% and 67% removal, respectively, for the same compounds. The removal efficiencies were examined for an initial concentration range of 20 to 120?μg/L for both MIB and geosmin.     

Effect of Nonsteady state H2O2 Tests on Oxygen Transfer Rate in Enhanced Biological Phosphorus Removal Process

A laboratory scale enhanced biological phosphorus removal process was operated in the University of Cape Town configuration to study the variations in alpha and oxygen transfer efficiency (OTEf) under different process conditions. As part of this investigation, process oxygen transfer parameters were determined using the steady state oxygen uptake rate (OUR) and the nonsteady state hydrogen peroxide addition (HPA) methods, as per the American Society of Civil Engineers guidelines. The results indicated that the oxygen transfer parameters [volumetric mass transfer coefficient (KLaf), oxygen transfer rate (OTRf), α and OTEf)] were higher when both methods were applied on the same day, compared to the subsequent period, when only the steady state OUR method was employed, under similar operating conditions. The difference in the oxygen transfer parameters appears to be due to the addition of H2O2 that generates reactive oxygen species in the nonsteady state HPA test. Based on the findings, it was concluded that the HPA test was not a suitable technique to measure oxygen transfer under process conditions. Further, a conceptual model hypothesizing the impacts of H2O2 addition on activated sludge process is presented.     

Laboratory Study of Successive Soil Saline Leaching and Electrochemical Lead Recovery

This research is related to a laboratory study on the performance of a successive soil saline leaching and electrochemical lead recovery process for soil decontamination. Erlenmeyer leaching assays showed that the addition of 5.5 mol NaCl/L in 25% (w/w) of soil pulp density maintained at pH 3.0 was found the most effective condition for Pb leaching. Under these conditions, 65% of Pb was leached from soil. Electrochemical treatment using an iron–monopolar electrode system operated at a current intensity of 3.0 A was able to reduce Pb content in soil leachate from 650 to 0.15 mg/L and this without production of metallic residue. Then, a leaching tank reactor and electrolytic cell coupled in a closed loop showed that the Pb mass balance of extrants/intrants ratio indicated 99.0±1.6% of Pb was recovered. Likewise, 94.1% of chloride ions were reused in the leaching tank reactor after electrochemical treatment.     

BTEX Removal from Produced Water Using Surfactant-Modified Zeolite

Produced water (water generated during recovery of petroleum) contains large amounts of various hazardous organic compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX). With increasing regulations governing disposal of this water, low-cost treatment options are necessary. This study evaluated the effectiveness of surfactant-modified zeolite (SMZ) for removal of BTEX from produced water. The long-term effectiveness of SMZ for BTEX removal was investigated along with changes in sorption properties with long-term use. The results of these investigations show that SMZ completely removes BTEX from produced water up to a compound-specific capacity, and that SMZ can be regenerated via air sparging without loss of sorption capacity. The BTEX mobility in laboratory columns of SMZ was in the order of decreasing water solubility and increasing Kow. The most soluble compound, benzene, began to elute at 8 pore volumes (PV), while the least soluble compounds, ethylbenzene and xylenes, began to elute at 50 PV. After treating 4,500 PVs of water in the column system over 10 sorption/regeneration cycles, no significant reduction in sorption capacity of the SMZ for BTEX was observed. The mean Kds determined in these column experiments ranged from 18.3?L/kg for benzene to 95.0?L/kg for p- and m-xylene. Laboratory columns were upscaled to create a field-scale SMZ treatment system. The field-scale system was tested at a natural gas produced-water treatment facility near Wamsutter, Wyo. We observed even greater sorption of BTEX in the field column than predicted from the laboratory results. In the field column, initial benzene breakthrough occurred at 10 PV and toluene breakthrough began at 15 PV, and no breakthrough of ethylbenzene or xylenes occurred throughout the 80 PV experiment. The field and laboratory results, along with the low price of SMZ (about $460?per?metric?t), suggest that SMZ has a potential role in a cost-effective produced water treatment system.     

Aerated Rock Filters for Enhanced Ammonia and Fecal Coliform Removal from Facultative Pond Effluents

Rock filters used to treat effluents from waste stabilization ponds do not remove ammonia as they are anoxic. A pilot-scale aerated rock filter was investigated, in parallel with an unaerated control, over an 18-month period to determine whether aeration provided conditions within the rock filter for nitrification to occur. Facultative pond effluent containing ～ 10?mg NH4–N/L was applied to the filters at a hydraulic loading rate of 0.15?m3/m3?day during the first 8?months and at 0.3?m3/m3?day thereafter. The results show that the ammonia and nitrate concentrations in the effluent from the aerated filter were <3 and ～ 5?mg?N/L, respectively, whereas the ammonia concentration in the effluent from the control filter was ～ 7?mg?N/L. Fecal coliforms were reduced in the aerated filter to a geometric mean count of 65?per?100?mL; in contrast the effluent from the control filter contained 103–104 fecal coliforms per 100?mL. Aerated rock filters are thus a useful land-saving alternative to aerobic maturation ponds.     

Removal of Mercury from Low-Concentration Aqueous Streams Using Chemical Reduction and Air Stripping

Field, laboratory, and engineering data confirmed the efficacy of chemical reduction and air stripping as a low concentration mercury treatment concept for water containing Hg(II). The process consists of dosing the water with low levels of stannous chloride [Sn(II)] to convert the mercury to elemental mercury (Hg0). Hg0 can easily be removed from the water by air stripping or sparging. We studied this concept for groundwater containing initial mercury concentrations of approximately 138 ng/L (0.00069 μmol/L). In undosed samples, sparging removed 0% of the initial mercury. Removal in the treated samples varied by reagent dose. Low reagent doses, with Sn:Hg stoichiometric ratios <1, showed little removal. High reagent doses, with Sn:Hg stoichiometric ratios greater than about 5 to 25, showed relatively complete removal (>94%) and yielded final mercury concentrations <10 ng/L (<0.00005 μmol/L). At intermediate doses, mercury removal was a function of the dose. A kinetic study indicated that addition of the Sn(II) reagent resulted in rapid reduction of Hg(II) to Hg0. When combined with standard supporting engineering techniques (e.g., treating the purge air) as needed, a simple system of chemical reduction and stripping may be useful and cost effective.     

Microbial Adaptability to Organic Loading Changes in an Enhanced Biological Phosphorus Removal Process

The enhanced biological phosphorus removal (EBPR) performances of phosphate-accumulating organisms (PAOs) under organic loading fluctuations were investigated using a sequencing batch reactor (SBR) with anaerobic/oxic stages. The adaptability of PAOs was evaluated after establishing a normal steady-state condition [chemical oxygen demand (CODin)=150 mg/L]. During SBR operation, the initial COD was changed gradually or abruptly. When the initial COD increased gradually from the steady state to 300 mg/L, the biomass increased steadily and the system showed stable EBPR. However, when the initial COD oscillated from 150 to 300 or 50 mg/L abruptly, PAOs could not adapt themselves to these sudden changes, resulting in unstable EBPR. When the organic loading returned to a normal condition, the system was recovered to stable EBPR in 2 days after the high organic loading fluctuation, while it was not after the low organic loading fluctuation. Using fluorescent in situ hybridization technique, Rhodocyclus-related PAO population changes were monitored. It was demonstrated that PAOs would wash out faster under the low organic loading fluctuation than the high organic loading fluctuation.