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1.
Water samples of the Passaúna River, Curitiba/Paraná (Brazil), were analyzed to determine total and thermotolerant coliform counts and Escherichia coli in order to provide information on human impacts on the water supply. Samples were collected and analyzed monthly, from March 2006 to February 2007, at five different locations along the river, and the multiple tube method was used to obtain total and thermotolerant coliform counts. The results varied from 130 MPN/100 mL to 1.6?×?106 MPN/100 mL for total coliforms, while for thermotolerant coliforms the variation was between 40 MPN/100 mL and 5?×?105 MPN/100 mL. The E. coli strains isolated from the samples were tested with 13 different antibiotics to determine their antibiotic resistance. The isolated strains were constantly sensitive to seven of the 13 antibiotics tested, and resistant to at least one of the other antibiotics. The results indicated that two factors could influence the increased contamination on this river, viz., seasonality parameters and domestic wastewater discharges. The determination of antibiotic resistance indices aimed to provide information on the anthropogenic influence. Only one of the locations investigated was considered critical due to the anthropogenic influence, with significant impacts from irregular domestic wastewater discharges.  相似文献   

2.
Harrison  R. B.  Turner  N. S.  Hoyle  J. A.  KrejsL  J.  Tone  D. D.  Henry  C. L.  Isaksen  P. J.  Xue  D. 《Water, air, and soil pollution》2000,124(1-2):205-215
Groundwater effluent sample collectors(zero-tension lysimeters) were installed directlybelow the drainfields of three residential onsitetreatment systems in the Clover/Chambers Creek aquiferregion of Pierce County near Tacoma, WA. The use of asplit effluent delivery system from the septic tank,where half the effluent was delivered under pressureto a normal native soil-only filter system and halfwas delivered to a sand filter system, allowed thedirect comparison of the two commonly-utilized septicsystems for treatment levels. Septic tank effluent(from the septic tank) and percolating water (between0.3 and 0.9 m beneath the effluent distributionlines) was collected between May 1991 and April 1994on 30 occasions. Samples were analyzed for fecalcoliform bacteria, nitrate, nitrite, ammonium andtotal reduced (Kjeldahl) nitrogen. Results of thisstudy indicate that the use of sand filters greatlyincreased removal of fecal coliform bacteria and totalnitrogen. Soil-only filter systems had an average of91% removal of fecal coliforms and 47%of total N; whereas sand filter systems had an averageof 99.8% removal of fecal coliforms and 80% of total N.  相似文献   

3.
The objective of this study is to examine the reuse of wastewaterfor beneficial purposes. To accomplish this objective, the efficiency of slow sand filters in removing total coliforms (TC) was studied using a probabilistic method. Three pilot scale slowsand filters were constructed at Alkhobar wastewater treatment plant, Dhahran, Saudi Arabia. The removal efficiency of filters was estimated under different operating control parameters, which included filtration rate (q), sand bed depth (d) and sand grain size (c). The Type III extreme value distribution best fitted theremoval efficiency data. A multiple linear regression analysis was performed to develop a relationship for mean removal efficiency as a function of control parameters. The predicted mean response and experimental results of previous studies werecompared to validate the empirical regression model. The controlparameters and influent concentrations of total coliform were used in Monte Carlo (MC) simulations for calculating the reliability index (β). The reliability index and corresponding risk were calculated for lognormally distributedsafety margins (SM). An effluent standard of 100 total coliform/100 mL was defined as capacity of the filter to ascertainthe risks of exceedence, which was approximately less than 50 for95% of the time. Pre and/or post disinfection would be necessaryto meet the stipulated effluent standards for unrestricted agriculture use.  相似文献   

4.
Over the course of a year a series of samples were taken from a wastewater treatment plant handling domestic sewage at each stages of the process, to detect the presence of enteric viral and classical bacterial indicators, and physicochemical parameters. The viruses were isolated on BGM cell cultures and counted according to the Most Probable Number method. The values of enteric viruses varied from 102 to 104/L in raw sewage and from 100 to 103 in final effluent. The efficiency of the plant at each stages during processing was evaluated. The parameters analysed show a systematic reduction of values between input and output, with average bacteriological reductions of 88% (fecal streptococci), 93% (fecal coliforms) and 94% (total coliforms), viral load reduced by 0–99%. COD and suspended solids showed a reduction of 61 % and 71% respectively. The 40% of isolated viruses were submitted to identification procedures using molecular techniques and pools of antisera. The viral types identified were enteroviruses (poliovirus and coxsackievirus B) and reoviruses. Viruses appear less easily removed than classical bacterial indicators. Reoviruses were removed less efficiently than enteroviruses.  相似文献   

5.
We undertook this study to determine the impact of urbanization on the microbial content of waters of a major recreational area of Lake Champlain. We followed changes in the numbers of total coliforms, fecal coliforms, fecal streptococci, and ascertained resistance of coliforms to heavy metals and antibiotics. We determined the distribution of these bacterial indicators of pollution by examining water and sediment samples. We also surveyed changes in physical parameters such as pH, temperature, turbidity, and wind direction to evaluate their effect on the examined aquatic microbial population. The level of all standard microbial indices of pollution frequently exceeded acceptable levels for recreational waters. Sediment samples indicated prolonged deposition of microbial pollutants, but efforts to demonstrate their release from sediment by dislocation and resuspension were inconclusive. We confirmed the presence of a population of heavy-metal and antibiotic-resistant coliforms isolated from harbor waters. Eighty-four percent of the total coliforms isolated from harbor water samples were resistant to one or more antibiotics and 96% were resistant to two or more heavy metals. The presence of these antibiotic resistant properties in coliforms, as well as elevated fecal coliform and fecal streptococci counts in both water and sediment samples, suggests to us that the bay is polluted by human fecal matter. This pollution probably emanates from south harbor sources and affects the shores of the major northern bathing area. It constitutes a potential hazard to public health because of the geophysical nature of the harbor and the location of the pollution source.  相似文献   

6.

The fate of wastewater effluents discharged from 17 septic tank disposal systems located near the shores of eight lakes in northeastern and eastern New York State was investigated. Fecal coliforms chloride, conductivity, dissolved 02, phosphate and various forms of N in ground water samples were analyzed. Of 46 ground water samples, 23 were found to be highly contaminated and 16 slightly contaminated. Only 7 were not contaminated by the wastewater effluent. Seventeen of the 23 highly contaminated samples were collected within 30.5 m of the discharge point of the septic systems. Eleven of these were collected from ground water less than 122 cm below ground level. Eight of the 16 slightly contaminated samples and 3 of the 7 noncontaminated samples were collected at a distance greater than 30.5 m. The depth to the ground water from ground surface and the distance of the ground water from the discharge point of the sewage system are main factors influencing pattern and severity of ground water contamination. This survey indicated that significant nutrient and fecal coliform contamination of lakeshore ground waters was occurring.

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7.
A study was carried out in order to estimate the presence of enteric and non-enteric indicators in the water distribution systems of Western Greece and to evaluate different methods for culture and isolation of coliforms in that region, under several incubation conditions and using different media. According to the different media and techniques used, the numbers of water samples found unsafe for consumption represented 21, 17 and 10% of the total, when mT7 agar, M-Endo agar LES (Membrane Filtration technique) and Most Probable Number (MPN) techniques were used, respectively. In one third of the samples oxidase positive microorganisms were present, which were almost eliminated by using anaerobic incubation of the media. Faecal streptococci were found only in 5% of the samples tested. The MPN technique proved to be significantly less efficient in recovering the coliform colonies than the Membrane Filtration (MF) technique (x2 = 125.758 < 182.405). The use of m-Endo agar LES and mT7 agar showed no statistically significant difference in detecting total coliforms (x2 = 162.55 > 162.422). However, a larger mean number of colonies per sample developed on mT7 agar, indicating that the latter medium should be used in our region for the detection of total coliforms.  相似文献   

8.
Most tidal creeks in North Carolina are closed or partially closed to shellfishing. These creeks often remain closed due to the inability to determine sources of fecal pollution. This study was designed for intensive fecal coliform monitoring of Futch Creek, N.C., to try and determine sources(s) of fecal pollution. Futch Creek is a mildly polluted tidal creek, with marginal levels of fecal coliforms and could potentially be reopened. Problems in interpreting levels of fecal coliforms and pollution risks are two fold and were extremely pronounced in this study. First, several environmental factors have been shown to influence levels of fecal coliforms. Therefore, effects of temperature, salinity, tidal cycles, and rain events on fecal coliform counts were examined. There were higher fecal coliform levels in the warmer temperatures. There was a strong inverse relationship with salinity, with highest fecal coliform counts in the 10–14 g L-1 range for both the mFC and mTEC counts with no apparent source of pollution. This trend was also observed in three other tidal creeks. Tidal cycles did affect fecal coliform counts with substantially higher counts during low tide and appeared to be more important than rain events. It is apparent that when evaluating several stations in a creek, samples must be taken during the same tidal cycle stage in order to have comparative data. Counts obtained using the mTEC method were consistently higher than mFC counts in all salinity ranges. Basic taxonomic tests were performed on fecal coliforms isolated from three salinity regimes: 0 g L-1, 10–14 g L-1, and 23–26 g L-1. The mFC method in the 10–14 g L-1 (45%) and 23–26 g L-1 (70%) salinity range had the highest incidence of false-positive counts (non E. coli). The mTEC method also had the highest incidence of false-positive counts in the 23–26 g L-1 (27%) and 10–14 g L-1 (24%), none as high as the mFC method. Therefore, the mTEC method appears to be the better of the two but is still not an ideal approach.  相似文献   

9.
An investigation was carried out at pilot scale to test the feasibility of using the effluent of a rotating biological contactors (RBC) unit treating wastewater generated from a university campus. The objective of the study was to cerefully monitor the impact of wastewater irrigation on the soil, percolating water, crop growth and the pathogenic condition within the immediate vicinity of wastewater application. Experimental plots with three crops: alfalfa, radish and tomato were irrigated with fresh and waste waters. The irrigation water was applied by sprinklers. Each crop was given two sub-treatments: with fertilizer and without fertilizer. The physical and chemical properties of the soil, the crop yields, and subsurface drainage were measured. In most of the cases, the yields resulted from the uses of wastewater with fertilizer were compatible with those of the uses of freshwater with fertilizer. The washings of tomato fruits grown with wastewater were analyzed for fecal coliforms. It appeared that the fruit skins were free of viable fecal coliforms 24 hours after the wastewater application. Subsurface drainage analyses did not show any alarming levels of constituents irrespective of the source of the water: wastewater or freshwater. The wastewater irrigation applied for a season had no significant effect on a silty loam soil. With wastewater irrigation, slught changes in the soil porosity and salinity were observed.  相似文献   

10.
A bacteriological survey was performed on 155 untreated, individual, rural groundwater supplies which included drilled wells, dug wells, and springs. Of these, 105 exceeded the Environmental Protection Agency (EPA) maximum contaminant level of one total coliform per 100 mL. Repeat sampling for 87 of the unacceptable 105 supplies indicated that 76 again exceeded the EPA standard limit. Masked coliforms were detected through confirmation tests in 11 water supplies that exhibited excessive noncoliform colonies (> 50 CFUs/membrane filter). Also, 48% of the supplies contained fecal coliforms and 62% contained fecal streptococci. Bacterial densities were related to the type of water supply with drilled wells containing fewer total coliforms, fecal coliforms, fecal streptococci, and heterotrophic plate count bacteria than dug wells or springs. Water supplies that were shallower, older, and lacking adequate casing characteristically were more heavily contaminated with sanitary indicator bacteria than supplies that were deeper, of more recent construction, and with sufficient casing.  相似文献   

11.
Purpose

There is increasing public concern about the amount of fresh water used on New Zealand dairy farms and the adverse impacts that farm dairy effluent (FDE) has on the environment. FDE mainly consists of fresh water (99%) with a small amount of solid material (1%). There is an opportunity to treat FDE to remove the colloidal solid material and recycle the water to wash the farm yard.

Materials and methods

A new method of treating FDE has been developed. The method uses a coagulant to flocculate and settle the colloidal particles in the FDE and thus produce the clarified water for recycling. The research and development programme involved three stages: (i) standard laboratory jar tests to establish the amount of coagulant required to treat the FDE, (ii) large tank tests to confirm the effectiveness of the coagulant at a larger scale and (iii) construction and testing of two pilot plants. A pasture field trial was conducted to test the effect of the clarified water and treated effluent on plant production.

Results and discussion

The new method of treating FDE was highly successful in removing the colloidal material and producing clarified water that can be recycled to wash the farm yard. The average turbidity of the clarified water from the first pilot plant was 52 nephelometric turbidity units (NTU) (a 97% reduction in NTU compared to the original FDE) and the average Escherichia coli concentration was 9 cfu per 100 mL (a 99.99% reduction compared to the original untreated FDE). The average total-phosphorus (P) concentration of the clarified water was 1.8 g m?3 (94% reduction), dissolved reactive phosphorus (DRP) was <?0.1 g m?3 (99% reduction) and total nitrogen (N) was reduced by >?70% (from 200 to 61 g m?3). The average turbidity of the clarified water from the second pilot plant was <?20 NTU (a 99.5% reduction). There was no adverse impact from the land application of the clarified water or the treated FDE on plant growth.

Conclusions

A new method for treating farm dairy effluent was successfully developed that produced clarified water that could be recycled to wash the farm yard and had a lower potential risk of environmental impacts when applied to land than untreated FDE. Land application of the clarified water or the treated FDE had no adverse impact on plant growth.

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12.
Greywater is a potential resource of water that can be improved to meet the quality needed for irrigation. This study evaluated the performance of bark, activated charcoal, polyurethane foam and sand filters in removing biochemical oxygen demand (BOD5), surfactants, phosphorus, nitrogen and microbial indicators from greywater during start-up and steady state. In column experiments, 0.6?m high filters (diameter 20?cm) were fed for 113?days with artificial greywater at a hydraulic loading rate of 0.032?m3?m?2?day?1 and an organic loading rate of 0.014?kg BOD5 m?2?day?1. Bark and activated charcoal efficiently reduced the concentrations of organics (BOD5), surfactants (methylene blue active substances??MBAS), total phosphorus (Tot-P) and total thermotolerant coliform numbers, while sand and foam were less efficient. Bark, activated charcoal, foam and sand reduced influent BOD5 by 98, 97, 37 and 75?%; MBAS by >99, >99, 73 and 96?%; Tot-P by 97, 91, 36 and 78?%; and total nitrogen by 19, 98, 13 and 5?%, respectively. BOD5 and MBAS were efficiently reduced directly from start-up by bark and activated charcoal, while foam needed 30?days to achieve about 50?% reduction in BOD5. Bark was the most efficient filter in reducing thermotolerant faecal coliforms (2.4 log10), while foam achieved the lowest reduction (0.5 log10). Overall, bark and activated charcoal filters appeared to be the most suitable filters for improving greywater quality to reach irrigation quality in terms of organic matter reduction. Performance of these filters under higher and fluctuating loadings and the long-term sustainability of the filter materials need further investigation.  相似文献   

13.
We examined the impact of the effluent discharged from a freshwater (trout and related species) fish hatchery on the presence of antibiotic-resistant microorganisms in a small stream. There had been no documented use of antibiotics in the hatchery for at least 6 months prior to our study, although a variety of biocides were employed routinely for cleaning. Heterotrophic bacteria and Escherichia coli were isolated from both water column and sediment samples at sites above and below the discharge of the hatchery effluent as well as from the hatchery effluent itself. Randomly chosen isolates (≥96 isolates per site) were tested for their resistance to ampicillin, cephalexin, erythromycin, and tetracycline. Resistance to at least one antibiotic was found in greater than 30% of both the heterotrophic isolates and the E. coli isolates from each of the sites. There were no significant differences among the sites in the proportion of the heterotrophic isolates resistant to any specific antibiotic. The proportion of E. coli isolates resistant to tetracycline in the hatchery effluent and in both the downstream water and sediment samples was significantly higher than in either the upstream water or sediment. These results support the possibility of the hatchery as a source of tetracycline-resistant microorganisms even in the absence of recent use of this antibiotic.  相似文献   

14.
A central wastewater treatment facility was built in 1997 for the town of Suwannee that eliminated 850 inadequately operating on-site sewage treatment and disposal systems. During a study in 1989?C1990, Salmonella were detected in Suwannee River water samples upstream and downstream of the town of Suwannee. This study presents the findings of fecal coliform distribution between the years 1996 and 2009 in canals and the main stem of Suwannee River near the town of Suwannee, a coastal area in southeastern USA. Fecal coliforms were measured and assessed to evaluate the water quality before and after the installation of the central wastewater treatment facility. In the canals nearby the town of Suwannee, significant differences in fecal coliform concentrations were detected between the samples collected before and after the operation of the central wastewater treatment facility. Average fecal coliform of 537 most probable number (MPN)/100?ml in the canals in 1996 was reduced to 218?MPN/100?ml after the operation of wastewater treatment facility. The fecal coliform levels in canals decreased significantly in the last 13?years. Even though the average fecal coliform levels in the river was reduced from 170 to 86?MPN/100?ml before and after the installation of the wastewater treatment facility, respectively, the difference was not statistically significant.  相似文献   

15.
The present study examined the potential of someroughing filter media, prepared from locally availablematerials in removing organic matter and turbidityfrom surface water. Also, the study included testingthe efficiency of roughing filter followed by slowsand filter in minimizing the suspended load on thesubsequent water treatment steps. Based onmicroorganisms removal and turbidity data, filtermedia consisted of three layers of gravel ranked topamong six of the media tested, showing 84–100%removal for chlorophyll ‘a’ green algae, blue-greenalgae, diatoms, total algal count, bacterial count (at22 and 37 °C), total coliforms, faecal coliform,faecal streptococci, yeast and Candida albicans.Using slow sand filter after roughing filter improvedthe percentage removal of turbidity, where it reachedup to 83% after roughing filter while it reached 92%after slow sand filter. From the view point ofaesthetic quality of the filtered water, the resultsof the analyzed physico-chemical parameters showed nochange before and after the use of the roughing andslow sand filters.  相似文献   

16.
Two important environmental parameters could be identified as being the main causes of pipe borne water contamination in the City of Benin. These are the combined effects of rainfall and excessive construction work and, secondly, the lack or inadequacy of plumbing codes. To study the combined effects of rainfall and excessive construction on the contamination of water, samples were tested for total coliform using the multiple-tube fermentation test. Sites were chosen to allow for the comparison of the coliform counts in areas of comparatively insignificant construction to areas of excessive public construction. Results show that in the areas of heavy public construction, the curves for both the rainfall and the coliform counts in the consumer lines were skewed in the same manner. The peak rainfall was in September (437.I mm) which corresponds to peak coliform number in the consumer lines for both Zone A (62 coliforms/100 ml) and Zone B (60 coliforms/100 ml) for the same month. When compared to the area of insignificant public construction as shown in Zone C, rainfall had little or no effect on the coliform counts either at the pumping station or in the consumer line. The maximum number of coliforms recorded for the consumer line was 5/100 ml during the month of June. Results suggest that the high counts of coliforms in the Benin City water supply could be attributed primarily to the effects of construction which resulted in pipe breakage. During heavy rainfall and flooding, water under flood pressure enters the pipes through cracks, improperly tightened joints and damaged pipes. The improper enforcement of plumbing codes or lack of such codes was also identified as another cause of the water contamination as shown in Zone D. A study of the effects of water pipes passing through septic tank drain fields also shows that such effluents served as another source of major contamination. The highest recorded number for coliforms for the pipe-borne water just before entering the septic tank drain field was 12/100 ml and after it passed through the field the number had gone up to 60/100 ml. Artificial contamination of the septic tank effluents to try to detect leaks in the water pipes passing through the absorption field was investigated. The bacterial contaminant could be recovered in the pipe-borne water and the quantity was skewed in the same manner as total rainfall between periods of sampling.  相似文献   

17.
Coliform and faccal coliform were isolated from drinking water samples obtained from tap water (TW) and storage tanks (ST) in Baghdad city. All isolates were identified and tested for their resistance to twelve antibiotics. Bacterial identification revealed that Ent. cloacae and Kl. pneumoniae were the predominant organisms from TW and ST water samples, respectively. Overall, 66% of the isolates from TW and 38% from ST were resistant to one or more of the drugs tested. Ampicillin, Carbenicillin, Cefalotin and Colistin resistance in particular were more frequent among bacterial isolates. The overall frequency of multiple antibiotic resistance among bacterial isolates in TW and ST samples were 47% and 33%, respectively. All bacterial strains isolated from drinking water were sensitive to Rifampicin. Results demonstrated the need for periodical bacteriological examination of drinking water and restriction in the use of antibiotics in this country.  相似文献   

18.
The defined substrate technology (DST) method is a reagent system designed to enumerate specific target microbes(s) from a mixture of bacteria. The system simultaneously enumerates total coliforms and Escherichia coli directly from a water sample. The reagent contains o-nitrophenyl-beta-D-galactopyranoside (ONPG), which is hydrolyzed by total coliforms to produce a yellow chromogen, and 4-methylumbeilliferyl-beta-D-glucuronide (MUG), which is hydrolyzed and fluoresces when E. coli organisms grow. Noncoliform bacteria are suppressed and cannot metabolize the indicator nutrients. Nine laboratories participated in a field evaluation of the method, which covered a wide range of surface and subsurface water sources and water-processing modalities, including the examination of natural samples. The DST system was compared to multiple-tube fermentation (MTF) (quantitative) and presence-absence (P-A) (qualitative) Standard Methods formats. Comparison of water samples from natural sources by using the most probable number (MPN) procedure showed that the DST test was equivalent to the currently used MTF test. Results from the DST and the qualitative P-A procedure showed that these tests agreed with each other in 94% of the water samples analyzed. Specificity of the DST method was established by subculturing a species consistent with a total coliform or E. coli from each positive tube. Eight laboratories participated in a collaborative study of the method. Each laboratory received 3 concentrations of E. coli (organisms/100 mL); 10 (low); 60 (medium); and 120 (high). The DST test was inoculated from a split sample of each bacterial density in parallel with Standard Methods brilliant green lactose broth.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

19.
Washing-down parlours and standing areas, following milking on dairy farms, produce dairy soiled water (DSW) that contains variable concentrations of nutrients. Aerobic woodchip filters can remove organic matter, nutrients and suspended solids (SS) in DSW, but the effluent exiting the filters may have to be further treated before it is suitable for re-use for washing yard areas. The performance of a single-layer sand filter (SF) and a stratified SF, loaded at 20 L m?2 day?1, to polish effluent from a woodchip filter was investigated over 82 days. Average influent unfiltered chemical oxygen demand (CODT), total nitrogen (TN), ammonium–N (NH4–N), ortho-phosphorus (PO4–P) and SS concentrations of 1,991?±?296, 163?±?40, 42.3?±?16.9, 27.2?±?6.9 and 84?±?30 mg L?1 were recorded. The single-layer SF decreased the influent concentration of CODT, TN, NH4–N, PO4–P and SS by 39, 36, 34, 58 and 52 %, respectively. Influent concentrations of CODT, TNT, NH4–N, PO4–P and SS were decreased by 56, 57, 41, 74 and 62 % in the stratified SF. The single-layer SF and the stratified SF were capable of reducing the influent concentration of total coliforms by 96 and 95 %, respectively. Although a limited amount of biomass accumulated in the uppermost layers of both SFs, organic and particulate matter deposition within both filters affected rates of nitrification. Both types of SFs produced final water quality in excess of the standards for re-use in the washing of milking parlours.  相似文献   

20.
In this study, we investigate the effect of application rate and timing of liquid swine slurry on leaching of antibiotic-resistant bacteria (ARB) and their antibiotic resistance genes (ARGs) through soil columns. Swine slurry was added to laboratory soil columns at rates of 5000 or 30,000 gal ac?1. For both application rates, rainfall was applied at either 1, 7, or 21 days after slurry application. Column effluent and the top centimeter of soil in the columns were sampled post-rainfall for cultivable bacteria and quantitative PCR was used to quantify tetracycline, methicillin, β-lactam, and erythromycin resistance genetic determinants. We also conducted similar experiments using swine lagoon slurry spiked with antibiotic-resistant E. coli and Salmonella. We found that the concentration of ARB and ARG recovered in the column effluent following application of the swine lagoon slurry generally decreased with increasing lag time between slurry application and simulated rainfall, though most of these decreases were not statistically significant. Moreover, no statistically significant differences in CFU or GU concentration in the column leachate were observed between the low and high slurry application rates. In the experiments using swine slurry spiked with E. coli and Salmonella, concentrations of both microorganisms eluted from fine sand columns were affected by both slurry application rate and lag time; recovery of ARGs, however, was mostly unaffected, but some differences were observed. In columns packed with loamy sand, no recovery was detected in the column effluent for either organism and recovery of ARG was unaffected by manure application rate or rainfall lag time.  相似文献   

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