Sorption Isotherms and Kinetics of Sediment Phosphorus in a Tropical Reservoir

The sorption of phosphorus, in the form of dissolved phosphate, on aquatic sediments collected from the tropical Kranji reservoir in Singapore was investigated under oxic and anoxic conditions. Kinetic experiments on sediment samples, collected from three monitoring stations, show that the sorption process consists of fast and slow adsorption stages followed by an equilibrium stage in which further adsorption or desorption may take place. The periods for each stage are in the scale of minutes, hours, and days, respectively. About 67.3–96.6% of the sorption is completed in the first stage under oxic and anoxic conditions. First-order kinetic constants are estimated to be from 4.60 to 12.26 h?1 for the fast adsorption stage, from 0.15 to 0.71 h?1 for the slow adsorption stage, and from 0.005 to 0.028 h?1 for the equilibrium stage. There were no significant differences observed between the sorption kinetic rates under oxic and anoxic conditions. The sorption isotherms of dissolved phosphate are found to be approximately described by the Langmuir equation, taking into consideration the native adsorbed phosphorus. The sorption capacities in different stations are 4.77–10.34 mg∕g of dry sediment for oxic conditions and 2.28–6.01 mg∕g of dry sediment for anoxic conditions. System redox potential has an apparent effect on the sorption capacity. Estimations of the natively sorbed phosphorus show that the sediments of the Kranji reservoir have initial amounts of phosphorus, ranging from 6.29 to 33.46% of the maximum sorption quantity. The sorption constants obtained are comparable to those obtained in temperate regions but have higher adsorption capacities.     

Release of Polychlorinated Biphenyls from River Sediment to Water under Low-Flow Conditions: Laboratory Assessment

The diffusive release of polychlorinated biphenyls (PCBs) from sediments to water under low-flow conditions was measured for surficial sediments with different PCB concentrations collected from the Grasse River near Massena, N.Y. Data on PCB sediment-water equilibrium partitioning and PCB mass release flux from sediments were used to assess the extent and mass transfer rate of PCB release under low-flow conditions in the Grasse River. Microcosm studies were employed to evaluate the release flux of PCBs under quiescent conditions for various river sediments and sediment mixtures. The observed total-PCB release fluxes ranged from about 1 to 20 mg/m2?year, showing predominantly dichloro- through tetrachlorobiphenyls. Analyses of water column samples from the Grasse River under low-flow conditions also indicated the predominance of dichloro- through tetrachlorobiphenyls as in the microcosm tests. Data on PCB equilibrium partitioning between water and sediment were used to estimate sediment porewater concentrations, and these data combined with the microcosm flux data were used to estimate average, aqueous-boundary-layer total-PCB mass transfer coefficients of 0.3–1.5 cm/day. These values are consistent with estimates of mass transfer coefficients based on aqueous-boundary-layer correlations, and with PCB mass transfer coefficients inferred from the field data for low-flow conditions in the fall and winter (approximately 2 cm/day). The correspondence of the laboratory results with the field measurements and mass transfer rates demonstrates the usefulness of the microcosm technique for estimating fluxes of PCBs from river sediments under low-flow minimum bioturbation conditions.     

Evaluation of Hypolimnetic Oxygen Demand in a Large Eutrophic Raw Water Reservoir, San Vicente Reservoir, Calif.

Hypolimnetic oxygenation can improve water quality by decreasing hypolimnetic accumulation of reduced compounds that complicate potable water treatment. Historically, aeration systems have been undersized because designers have not accounted for increases in sediment oxygen demand (SOD) resulting from the operation of aeration systems. A comprehensive study was performed to estimate the hypolimnetic oxygen demand (HOD) in San Vicente Reservoir, a eutrophic raw water reservoir in San Diego. Chamber experiments confirmed that turbulence and oxygen concentration at the sediment-water interface dramatically affected SOD. Values ranged from under 0.2?g/m2/day under quiescent low-oxygen conditions to over 1.0?g/m2/day under turbulent high-oxygen conditions. Based on a statistical evaluation of historical oxygen concentrations in the reservoir and anticipated increases in SOD resulting from operation of an oxygenation system, a design HOD of 16,400?kg/day was estimated. This is approximately four times the HOD observed in the spring after the onset of thermal stratification. Laboratory chamber experiments confirmed that maintenance of a well-oxygenated sediment-water interface inhibited the release of phosphate, ammonia, iron, and manganese from sediments. In addition, hydrodynamic modeling using DYRESM-WQ showed that operation of a linear diffuser oxygenation system would not significantly affect thermal stratification.     

Nitrogen Transformations during Soil–Aquifer Treatment of Wastewater Effluent—Oxygen Effects in Field Studies

Depth-dependent oxygen concentrations and aqueous-phase total ammonia and nitrate/nitrite ion concentrations were measured in the field during the infiltration of wastewater effluent. Measurements illustrated the dependence of nitrogen fate and transport on oxygen availability. Infiltration basins were operated by alternating wet (infiltration) and dry periods. During infiltration periods, ammonia was removed within the top few feet of sediments via adsorption. Biochemical activity rapidly eliminated residual molecular oxygen in the infiltrate, making the soil profile anoxic. During dry periods, oxygen reentered the basin profile and sorbed ammonia was converted to nitrate via nitrification. Oxygen penetrated to a depth of about 0.6?m?(2?ft) within the first few days of dry periods. At greater depths, oxygen levels increased more slowly due to a combination of slow transport kinetics and biochemical (nitrogenous) oxygen demand. During normal wet/dry basin cycles consisting of about 4 wet and 4 dry days, the local vadose zone remained anoxic at depths greater than about 1.5?m?(5?ft) below land surface. As a consequence, conditions for denitrification were satisfied in the deeper sediments. That is, the nitrate nitrogen produced in near surface sediments moved freely downward with infiltrating water where it encountered an extensive anoxic zone before reaching local monitoring or extraction wells. The relative importance of dissolved organics and sorbed ammonia as electron donors for denitrification reactions remains to be established.     

Aerobic Biodegradation of Methyl Tert-Butyl Ether in Gasoline-Contaminated Aquifer Sediments

Intrinsic biodegradation of methyl tert-butyl ether (MTBE) in aquifer sediments under oxic conditions was investigated using laboratory microcosms. Aquifer samples were collected from three different areas (source area, upgradient, and downgradient) of a shallow gasoline-contaminated aquifer within the Atlantic Coastal Plain Province located in Virginia. Biodegradation of MTBE was observed in the source-area microcosms in which MTBE declined from a starting concentration of 2.7 to 0.28 mg/L over a 58-day period, following an initial lag period of 20 days. The same set of microcosms was respiked with MTBE to an initial concentration of 4.8 mg/L and MTBE concentrations declined to 0.20 mg/L over a 52-day period with no lag in biodegradation. First-order MTBE biodegradation rates for the first and second periods were 0.037±0.003 and 0.063±0.003 day?1, respectively. When another set of source-area microcosms was spiked with MTBE (5 mg/L), toluene and ethylbenzene (1 mg/L each), the initial lag period increased to 33 days but there was no significant change in the MTBE biodegradation rate (0.065±0.026 day?1) and MTBE was not detected after 134 days. Biodegradation of MTBE was also observed in the microcosms constructed using aquifer sediment with only limited exposure to MTBE but the degradation rate was lower and statistically different (0.022±0.005 day?1) than the source area microcosms. Biodegradation of MTBE ceased when oxygen was depleted. Methyl tert-butyl ether did not biodegrade in the uncontaminated, upgradient microcosms; however, rapid biodegradation of toluene was observed. Methyl tert-butyl ether biodegradation appears to be limited in the absence of dissolved oxygen and in aquifer sediments where petroleum hydrocarbons including MTBE were not previously observed.     

Prescribed medication and nutrition of social care patients in Crete, Greece

A Tn917 mutant of Staphylococcus carnosus TM300, nrIII, was isolated and characterized. Mutant nrIII did not take up nitrate or accumulate nitrite when grown in B-medium supplemented with up to 10 mM nitrate under anoxic conditions; however, it displayed wild-type levels of benzyl Delta viologen-linked nitrate reductase activity. Cultivated in B-medium with nitrate under oxic conditions, mutant nrIII accumulated fivefold less nitrite than the wild-type. The mutation in S. carnosus nrIII could be complemented with a 2-kb chromosomal EcoRI-HpaI fragment from the wild-type. The gene affected by transposon insertion in mutant nrIII was cloned and sequenced. Analysis of the deduced amino acid sequence revealed that this gene, designated narT, encodes a highly hydrophobic 42-kDa transmembrane protein of 388 amino acids and shows similarities to transport proteins that play a role in nitrate import or nitrite export. The inability of nrIII to take up nitrate under anoxic conditions and its ability to take up and accumulate nitrite in the presence of benzyl viologen, a nitrate ionophore, under the same conditions suggest that NarT represents a transport protein required for nitrate uptake under anoxic conditions in S. carnosus.     

Anoxic∕Oxic Biodegradation of Aminobenzene

Biodegradation of aminobenzene, which is used as the only source of carbon and nitrogen, is evaluated in a single fluidized bed reactor operated in a temporal, anoxic∕oxic mode. The experimental evidence indicates that total organic carbon (TOC) is removed with >91% efficiency at a feed concentration of 100 mg∕L and a dilution rate of 2.4 day?1. Moreover, about 53–63% of feed total Kjeldahl nitrogen (TKN) is also removed, confirming that effective removal of nitrogenous matter in aminobenzene (i.e., the ?NH2 group) is achievable in a temporal, anoxic∕oxic environment. The kinetic analysis shows that TOC removal in oxic cycles is rapid and substantial, which enables nitrification to proceed at a discernible rate. In addition, the data on TOC and NO3?-N removal in anoxic cycles reveal that carbonaceous matter in aminobenzene and∕or its intermediate metabolites is effectively utilized for denitrification. The best treatment performance, in terms of carbon and nitrogen removal and potential savings in aeration costs, is obtained by coupling a 6 h oxic cycle with a 6 h anoxic cycle. All reaction rates estimated in anoxic∕oxic experiments remain relatively constant over the range of conditions tested.     

Effect of Cd(II) on Different Bacterial Species Present in a Single Sludge Activated Sludge Process for Carbon and Nutrient Removal

Heavy metal cadmium(II) was added stepwise into an A2O pilot plant to investigate the toxic effects of Cd(II) on the removal efficiencies, kinetic parameters (yield coefficients and maximum specific growth rates) and reaction rates of carbon, nitrogen and phosphate for the acclimatized heterotrophic and autotrophic bacteria. Results showed that 2?mg/L Cd(II) initially affected the biological reaction of phosphate removal. At Cd(II) 5?mg/L, the efficiencies of total nitrogen removal and nitrification were substantially dropped. At the same time, the yield coefficient and maximum specific growth rate of heterotrophs were significantly decreased from 0.8?g?COD/g?COD and 6.44?day?1 to 0.54?g?COD/g?COD and 4.67?day?1, respectively. And, the denitrification rate was inhibited by about 61%. The inhibition percentages of anaerobic release, anoxic and aerobic uptake rates of phosphate were about 76, 64, and 90%, respectively. When Cd(II) concentration was continually increased up to 35?mg/L, removal efficiency of chemical oxygen demand (COD) was significantly dropped. However, there was no obvious inhibition on the biological reactions of anaerobic ammonification.     

Estimating Pollutant Mass Accumulation on Highways during Dry Periods

For determining the accumulated pollutant mass on highways, two years of monitoring data were used from eight highway sites in southern California. Buildup over antecedent dry days was calculated from mass washed off from the following storm and retained pollutant mass. Mass accumulation rates were determined for total suspended solids (TSS), chemical oxygen demand (COD), oil and grease, total Kjeldahl nitrogen, and total phosphorus, and are reported in g/m2-day. A revised buildup model is proposed using an alternative modeling approach to describe buildup during dry days between storms. The result shows that, between 1 and 10 antecedent dry days, the pollutant mass buildup rates are determined to be 0.544?g/m2-day for TSS, 0.114?g/m2-day for COD, and 0.0113?g/m2-day for oil and grease. Buildup rates decline in subsequent periods rates decreased by 79% for TSS, 78% for COD, and 61% less for oil and grease in the following 10–70?day period.     

Effects of Nutrient Source and Supply on Crude Oil Biodegradation in Continuous-Flow Beach Microcosms

Ammonium and nitrate were used as nitrogen sources to support microbial biodegradation of crude oil in continuous-flow beach microcosms to determine whether either nutrient was more effective in open systems, such as intertidal shorelines. No differences in the rate or extent of oil biodegradation were observed, regardless of whether these nutrients were provided continuously or intermittently. Nutrients were provided once every two weeks to intermittent-input microcosms and washed out within four to five days. In continuous-input microcosms, ammonium and nitrate were assimilated as quickly as they were provided during the first week, but both accumulated to greater than 10?mg?N/L thereafter. The sensitivity of the oil mineralization rate to nutrient input decreased rapidly as the extent of oil degradation increased, and after about two weeks the rate of oil-mineralization appeared to be independent of nutrient input. Therefore, there may be little value in maintaining a long-term supply of nutrients in contact with oil-contaminated sediments. The rates of microbial assimilation of ammonium and nitrate followed similar trends. Both compounds were assimilated more slowly as the extent of oil biodegradation increased, and the nitrate uptake rates approached zero after about two weeks. Ammonium assimilation continued at a low rate throughout the six-week experiment, but this did not appear to affect the rate of oil mineralization. Assimilation of ammonium resulted in a sharp decrease in the pH of the synthetic seawater that was pumped continuously through the microcosms, but nitrate had a much smaller effect on pH. The magnitude of the ammonium-associated pH change was never as large as was observed in previous studies involving oil biodegradation in batch reactors, however, and did not affect the oil-biodegradation rate.     

Evaluation of Nutrient Release from Sediments of Artificial Lake

This study examined nutrient fluxes between sediment and water with a laboratory-scale benthic chamber. This research targeted an artificial lake that had undergone water-quality problems. Two sites at Lake Asan, Site A in the vicinity of the dam and Site B at the inflow of the lake, were selected and characteristics of the sediments and their influence on the water quality of the lake were evaluated. Most of the inorganic phosphorus in the study area was in the form of apatite and nonapatite phosphorus (91.9% of Site A, 83.3% of Site B). Site B, with a fast-stream velocity, had larger particle size, smaller nutrient level, and smaller amounts of inorganic phosphorus than Site A. The benthic chamber experiment showed that overall fluxes of Site A were as follows: ammonia is 0.003??μmol?cm-2?day-1, nitrate is -0.067??μmol?cm-2?day-1, and phosphate is 1.049??nmol?cm-2?day-1. Site B showed an increase in phosphate concentration after a dissolved oxygen (DO) drop (<3??mg/l), which resulted in smaller negative nitrate fluxes (-0.043??μmol?cm-2?day-1), larger positive ammonia (0.137??μmol?cm-2?day-1), and larger phosphate fluxes (2.120??nmol?cm-2?day-1) than at Site A. The movement of nutrients at the sediment-water interface was more sensitive to environmental conditions such as DO than other factors, such as sediment characteristics and chemical forms of nutrients. On the basis of the fluxes obtained from the benthic chamber, positive values are estimated for both phosphorus and nitrogen release rates. This indicates that during the sampling period sediment acted as a source of nitrogen as well as phosphorus to the overlying waterbody.     

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.     

Effect of Increasing Nitrobenzene Loading Rates on the Performance of AMBR and Sequential AMBR/CSTR Reactor System

A laboratory scale sequential anaerobic migrating blanket reactor (AMBR)/aerobic completely stirred tank reactor (CSTR) system was operated to investigate the effect of increasing nitrobenzene (NB) concentrations on the performance of AMBR/CSTR reactor system. The reactor system was operated at increasing NB loading rates from 1.93?to?38.54?g?NB?m?3?day?1 and at a constant hydraulic retention time of 10.38?days. In this study, chemical oxygen demand (COD) and NB removal efficiencies, variations of bicarbonate alkalinity (Bic.Alk.), total volatile fatty acid (TVFA), and total methane gases were monitored. COD removal efficiencies were 93–94% until a NB loading rate of 5.78?g?m?3?day?1 in the AMBR reactor. For maximum COD removal, the optimum NB loading rate and NB concentration were found to be 5.78?g?m?3?day?1 and 60?mg?L?1, respectively. COD removal efficiencies decreased from 94 to 87% and to 85% at NB loading rates of 1.93–28.90 and 38.54?g?m?3?day?1, respectively. COD was mainly removed in the first compartment. NB removal efficiencies also were approximately 100% at all NB loading rates in the effluent of the AMBR reactor. The maximum total gas and methane gas productions were found to be 2.8?L?day?1 and 1.3?mL?day?1, respectively, at a NB loading rate of 5.78?g?m?3?day?1. The TVFA concentration in the effluent of AMBR was low (17?mg?L?1) at a NB loading rate as high as 38.54?g?m?3?day?1. Overall COD removal efficiencies were found to be 99 and 96% at NB loading rates of 1.93 and 38.54?g?m?3?day?1, respectively, in a sequential AMBR/CSTR reactor system. In this study, NB was reduced to aniline under anaerobic conditions. Aniline removal efficiencies were 100% until a NB loading rate of 17.34?g?m?3?day?1 in aerobic CSTR reactor while aniline removal efficiency decreased to 90% at a NB loading rate of 38.54?g?m?3?day?1 in an aerobic reactor. In the aerobic step, aniline was mineralized to catechol. The contribution of aerobic step is not only the degradation of aniline, it may also increase the COD removals from 85 to 99% at a NB loading rate as high as 38.54?g?m?3?day?1.     

Characterization of Methane Flux and Oxidation at a Solid Waste Landfill

Methane emissions were measured at several locations at a typical solid waste facility using a static chamber technique. At the entire facility, methane flux varied from ?13.6?to?1,755?g?m?2?day?1. The flux data had an arithmetic mean value of 71.3?g?m?2?day?1 and a geometric mean value of 18.6?g?m?2?day?1. At this site, methane emission was generally lower on the side slopes relative to the flat areas of the landfill. The spatial variability of methane flux was characterized by point kriging and inverse distance weighing (IDW) in an intensive study of a 61×61-m area. The geospatial means in this area obtained by both methods were almost identical (20.9 versus 20.8?g?m?2?day?1). These geospatial means for the area were also similar to the arithmetic mean (24.5?g?m?2?day?1), but 3.4 times the geometric mean (6.5?g?m?2?day?1). Methane oxidation was evaluated at the surface of the landfill and at several depths within the cover soil using stable isotope techniques. The δ?13C of CH4 averaged ?55.4% in the anoxic zone. Methane collected in chambers and in surficial soil probes exhibited more 13C enriched values, ranging from ?55.4 to ?34.5%, due to the preferential uptake of 12CH4 by methanotrophic bacteria. Methane oxidation at the landfill averaged 22% and occurred in the upper 70?cm of the landfill cover soil. Oxidation occurred in all tested locations of the landfill and for all ages of buried waste.     

Anoxic Biological Phosphorus Uptake∕Release with High∕Low Intracellular Polymers

This study investigates the denitrification∕phosphate uptake and denitrification∕phosphate release characteristics among denitrifying phosphate accumulating organisms (DNPAO), denitrifier, and nondenitrifying phosphate accumulating organisms (non-DNPAO) in a biological nutrient removal process named TNCU-I, using a series of anoxic batch experiments with and without added acetate under high∕low intracellular polymer conditions. The results showed 47% phosphate uptake in the anoxic tank of the TNCU-I process. Additionally, due to the combined attribution of denitrifier and DNPAO, the experiments with both added acetate and phosphate produced higher denitrification rates than experiments with only acetate added. Furthermore, DNPAO contributed 42% of the denitrification reaction. The sludge exhibited simultaneous phosphate uptake and release under anoxic conditions when acetate was added. When no acetate was added, the specific phosphate uptake rate for the high intracellular polymer level was higher than that found at the low intracellular polymer level. Moreover, the phosphate uptake rate of non-DNPAO was observed to be 2.46 times greater than that of the DNPAO. The phosphate uptake per unit polyhydroxyalkanoates (PHA) consumption (γPO4/PHA) for the non-DNPAO was 1.08 times greater than that of DNPAO. Thus, this study demonstrates that the utilization efficiency of PHA by non-DNPAO is not significantly different with the utilization efficiency of PHA by DNPAO.     

The anaerobic oxidation of ammonium

From recent research it has become clear that at least two different possibilities for anaerobic ammonium oxidation exist in nature. 'Aerobic' ammonium oxidizers like Nitrosomonas eutropha were observed to reduce nitrite or nitrogen dioxide with hydroxylamine or ammonium as electron donor under anoxic conditions. The maximum rate for anaerobic ammonium oxidation was about 2 nmol NH4+ min-1 (mg protein)-1 using nitrogen dioxide as electron acceptor. This reaction, which may involve NO as an intermediate, is thought to generate energy sufficient for survival under anoxic conditions, but not for growth. A novel obligately anaerobic ammonium oxidation (Anammox) process was recently discovered in a denitrifying pilot plant reactor. From this system, a highly enriched microbial community with one dominating peculiar autotrophic organism was obtained. With nitrite as electron acceptor a maximum specific oxidation rate of 55 nmol NH4+ min-1 (mg protein)-1 was determined. Although this reaction is 25-fold faster than in Nitrosomonas, it allowed growth at a rate of only 0.003 h-1 (doubling time 11 days). 15N labeling studies showed that hydroxylamine and hydrazine were important intermediates in this new process. A novel type of hydroxylamine oxidoreductase containing an unusual P468 cytochrome has been purified from the Anammox culture. Microsensor studies have shown that at the oxic/anoxic interface of many ecosystems nitrite and ammonia occur in the absence of oxygen. In addition, the number of reports on unaccounted high nitrogen losses in wastewater treatment is gradually increasing, indicating that anaerobic ammonium oxidation may be more widespread than previously assumed. The recently developed nitrification systems in which oxidation of nitrite to nitrate is prevented form an ideal partner for the Anammox process. The combination of these partial nitrification and Anammox processes remains a challenge for future application in the removal of ammonium from wastewater with high ammonium concentrations.     

BTX Biodegradation in Activated Sludge under Multiple Redox Conditions

Activated sludge sequencing batch reactors were used to study BTX biodegradation under anoxic (denitrifying), microaerobic, and aerobic conditions. Toluene and m-xylene were biodegraded under denitrifying conditions, and the loss of these compounds correlated with the activity of reducing enzymes that were capable of oxidizing methyl viologen. Although benzene, p-, and o-xylene were recalcitrant under anoxic treatment, all three were biodegraded under microaerobic [<0.2 mg∕L dissolved oxygen (DO)] and nitrate or nitrite (NOx)-supplemented microaerobic conditions. Methyl viologen oxidation potential decreased under all microaerobic conditions while catechol 1,2-dioxygenase (C12O) and catechol 2,3-dioxygenase (C23O) were induced, indicating that the aromatic hydrocarbons were metabolized by aerobic pathways, even in the presence of NOx and in the absence of measurable DO. The degree of C12O and C23O expression under microaerobic conditions was comparable to levels found under aerobic (DO > 4 mg∕L) conditions. Benzene, p-, and o-xylene were biodegraded twice as fast under NOx-supplemented compared to NOx-free microaerobic conditions, and specific biodegradation rates under aerobic and NOx-supplemented microaerobic conditions were comparable. Oxidation reduction potential successfully differentiated between the various electron acceptor conditions and proved to be a sensitive indicator.     

Environmental Factors and the Application of Hydrogen Peroxide for the Removal of Toxic Cyanobacteria from Waste Stabilization Ponds

Toxin-producing cyanobacteria constitute a serious threat to human and environmental health. It is thus essential that an effective treatment guarantees the removal of cyanobacteria from wastewater before its inclusion in water recycling or environmental flow. Hydrogen peroxide (H2O2) has been shown to induce cyanobacterial decay in laboratory cultures. However, its application for the removal of cyanobacteria from wastewater treatment ponds under environmental conditions has not been investigated. To examine the effects of environmental factors, field trials were performed at both the mesocosm and full-scale levels. The mesocosm trial was completed under field conditions of incident radiation, with various H2O2 concentrations. A concentration of 1.1×10-4??gH2O2/μg chl-a resulted in a 32% decrease in cyanobacterial concentration after 24?h, and this approximate concentration was then applied to a wastewater treatment pond in the full-scale trial. In the full-scale experiment, intense spatial and temporal monitoring of phytoplankton concentrations and temperature throughout the pond was performed. Cyanobacterial biomass was reduced by 57% and total phytoplankton biomass by 70% within 48?h of H2O2 addition. Mixing and radiation were shown to control the depth reached by H2O2 following addition to the ponds. The synergistic effect of H2O2 addition with environmental factors increased the effectiveness of cyanobacterial removal compared with laboratory experiments. The concentration of H2O2 required for the removal of cyanobacteria under field conditions may be decreased from laboratory studies by an order of magnitude.     

Evaluation for Biological Reduction of Nitrate and Perchlorate in Brine Water Using the Hydrogen-Based Membrane Biofilm Reactor

Whereas ion exchange is an attractive technology for treating perchlorate and nitrate in drinking water, a major disadvantage is that the resin must be regenerated using a brine, producing wastes with high concentrations of nitrate, perchlorate, and salt. This study investigates the potential for simultaneous nitrate and perchlorate reductions in high-salt conditions using the H2-based membrane biofilm reactor (MBfR). The autotrophic biological reductions produce harmless N2 and Cl?, making the brine safe for reuse or disposal. A very high-strength brine ( ～ 15% salt) from a commercial ion-exchange membrane, Purolite, supported biofilm accumulation and allowed slow reduction rates for nitrate and perchlorate. Reduction rates increased significantly when the Purolite brine was diluted by 50% or more. A synthetic high-strength salt medium containing nitrate, perchlorate, or both supported more rapid reduction rates for as high as 20?g/L ( ～ 2%) NaCl, while 40?g/L NaCl slowed reduction by 40% or more, confirming that the microorganisms in the MBfR were inhibited by high salt content. An increase of H2 pressure gave higher fluxes for 20?g/L NaCl, demonstrating that H2 availability controlled the reduction kinetics when the system was not salt-inhibited.     

Nitrogen Removal Using Combined Ultracompact Biofilm Reactor-Packed Bed System

A predenitrification system consisting of an ultracompact biofilm reactor (UCBR) and a packed bed column was used for removing nitrogen from synthetically simulated wastewater. The UCBR column was maintained under aerobic conditions to favor nitrification process, while the packed bed column was operated under an anoxic environment for denitrification process. A peristaltic pump was used to recycle fluid between the anoxic-packed bed and aerobic-UCBR columns to facilitate nitrogen removal. Five recycle ratios (R) were investigated, namely, 3, 4, 5, 6, and 10. The highest average total nitrogen (TN) removal rate was achieved at R = 4. The NH4+–N, TN, and chemical oxygen demand (COD) removal rates at this R were 0.56±0.05?kg NH4+–N/m3/day, 0.39±0.09?kg TN/m3/day, and 1.83±0.18?kg COD/m3/day, respectively. It was noted that poor nitrification in the UCBR was accompanied by a corresponding reduction in overall TN removal efficiency. This observation suggested that nitrification process was the limiting step for TN removal in this setup. Thus, the performance of this predenitrification system could be enhanced by optimizing the performance of the nitrification process.