Dissolved-Oxygen/Suspended-Solids Concentration Relationships in the Upper Humber Estuary

Results of dissolved-oxygen concentration from continuous monitors at one location on the (Yorkshire) tidal Ouse and two locations on the tidal Trent have revealed a strong dependence upon the concentration of suspended sediment. High concentrations of sediment lead to a lowering in dissolved-oxygen levels. A comparison of this effect between the two rivers reveals lower dissolved-oxygen concentrations in the River Ouse than in the River Trent for a given concentration of suspended sediment, which is partly due to a difference in the quality and quantity of pollutant discharges into the Ouse compared with the Trent. Because the concentration of suspended solids at a given location is known to be dependent upon the fresh-water flow and the tidal range, it is concluded that the dissolved-oxygen concentration is also strongly dependent upon conditions of fresh-water flow and tidal range for these two tidal rivers.     

The geographic distribution of fluoride in surface and groundwater in Ethiopia with an emphasis on the Rift Valley

This paper analyzes the most extensive database on fluoride distribution in Ethiopia. Of the total 1438 water samples tested, 24.2% had fluoride concentrations above the 1.5 mg/l recommended optimum concentration recommended by WHO. Regionally, by far the highest fluoride levels were recorded in the Rift Valley, where 41.2% of all samples exceeded the 1.5 mg/l level. Only 1.0% of the samples from the central and northwestern highlands and 10.0% in the southeastern highlands exceeded 1.5 mg/l. Larger proportions of deep wells (50.0%) and hot springs (90.0%) than shallow wells (27.2%) and cold springs (12.6%) exceeded the 1.5 mg/l level. The highest fluoride concentrations were recorded for Rift Valley lakes Shala (264.0 mg/l) and Abijata (202.4 mg/l) and the lowest in Lake Tana, and rivers, wells and springs in the highlands. The fluoride concentrations of the Awash River, which originates in the highlands and flows through the Rift Valley, increase downstream, giving concern over the current diversion of high-fluoride water from Lake Beseka. Of the various flourosis prevention methods tried in Ethiopia, the treatment of surface water has been shown to be the most feasible and effective for towns and large commercial farms in the Rift Valley, although defluoridation methods should be considered for smaller rural communities.     

STORMWATER QUALITY ASSOCIATED WITH A FULL SILT TRAP DISCHARGING INTO AN URBAN WATERCOURSE

The aim of this project was to assess the influence of a full silt trap on the quality of stormwater which was discharged into an urban watercourse. The average SS concentrations of the outflow were 2.0 and 34.1 mg/l during dry-weather and wet-weather conditions, respectively, and SS concentrations of up to 141.6 mg/l were recorded during storms. Treated stormwater SS concentrations were often high, compared with secondary sewage-treatment standards of ≤30 mg/l. Pollutants accumulated in the silt trap.     

Stormwater quality associated with a silt trap (empty and full) discharging into an urban watercourse in Scotland

The aim was to assess the influence of a full silt trap at the end of a stormwater drainage pipe on the water quality of stormwater discharged into a semi‐natural urban watercourse. For approximately eleven weeks, the water qualities of the preliminarily treated stormwater and of the receiving watercourse (Braid Burn) were studied. The mean outflow concentrations of suspended solids were 2.0 mg/l and 34.1 mg/l during dry and wet weather conditions, respectively. Suspended solids concentrations of up to 141.6 mg/l were recorded during storm events. Suspended solids values for treated stormwater were often too high compared to international secondary wastewater treatment standards of around 30 mg/l. Pollutants including heavy metals (e.g., zinc, copper and nickel) accumulated in the silt trap. However, high outflow velocities during heavy rainfall events did not result in clearly defined sediment layers due to sediment re‐suspension. Metals did not accumulate in the receiving watercourse.     

Is in-stream processing an important control on spatial changes in carbon fluxes in headwater catchments?

Data on small-scale spatial variations in instantaneous fluxes and concentrations of dissolved organic carbon (DOC), dissolved inorganic carbon (DIC) and free carbon dioxide (CO2) are presented for a small acidic headwater stream in NE Scotland. Chloride is used as a conservative element to estimate additional, diffuse inputs of water into the main stem of the stream, other than those from tributaries. Downstream changes in instantaneous carbon fluxes were calculated and then used to estimate losses and gains of carbon within the stream system. Dissolved organic carbon concentrations in the stream ranged from 1.19-6.06 mg l(-1) at its source to a maximum of 10.0-25.3 mg l(-1) as the stream passed through deep peats; DOC concentrations then declined in the lower part of the catchment. DIC concentrations were initially low, increased to 1.5-3.0 mg l(-1) and then decreased to 0.1-1.65 mg l(-1) at the lowest site. Free CO2 concentrations increased from 0.35 mg l(-1) at the stream source to 3.30 mg l(-1) as the stream passed through the peat dominated area. Continually high inputs of CO2-rich water (> 6.0 mg l(-1)) from tributaries maintained these high concentrations in the main stem, until approximately 1.74 km downstream, when there was a rapid decline in concentration. Significant changes in DOC, DIC and CO2 fluxes occur over a distance of 2.7 km downstream from the stream source to the catchment outlet. Between 5.64-41.5 mg C s(-1) as DOC and 2.52-16.2 mg C s(-1) as DIC are removed from the water column. Between 6.81 and 19.0 mg C s(-1) as CO2 is lost along the stream length as progressive equilibration with the atmosphere occurs. We estimate that 11.6-17.6% of the total DOC flux is removed from streamwater by in-stream processes. Dissolved inorganic carbon (HCO3- and free CO2) losses are in excess of nine times its measured flux at the outlet of the catchment. These results suggest that in-stream processing of DOC and DIC and outgassing of CO2 are important controls on the spatial variability of carbon fluxes within headwater streams in upland catchments dominated by organic-rich soils.     

Phenol biodegradation and its effect on the nitrification process

Phenol biodegradation under aerobic conditions and its effect on the nitrification process were studied, first in batch assays and then in an activated sludge reactor. In batch assays, phenol was completely biodegraded at concentrations ranging from 100 to 2500 mg l(-1). Phenol was inhibitory to the nitrification process, showing more inhibition at higher initial phenol concentrations. At initial phenol concentrations above 1000 mg l(-1), the level of nitrification decreased. In the activated sludge reactor, the applied ammonium loading rate was maintained at 140 mg N-NH(4)(+)l(-1)d(-1) (350 mg N-NH(4)(+)l(-1)) during the operation time. However, the applied organic loading rate was increased stepwise from 30 to 2700 mg COD l(-1)d(-1) by increasing the phenol concentration from 35 up to 2800 mg l(-1). High phenol removal efficiencies, above 99.9%, were maintained at all the applied organic loading rates. Ammonium removal was also very high during the operation period, around 99.8%, indicating that there was no inhibition of nitrification by phenol.     

Occurrence of organic wastewater compounds in effluent-dominated streams in Northeastern Kansas

Fifty-nine stream-water samples and 14 municipal wastewater treatment facility (WWTF) discharge samples in Johnson County, northeastern Kansas, were analyzed for 55 compounds collectively described as organic wastewater compounds (OWCs). Stream-water samples were collected upstream, in, and downstream from WWTF discharges in urban and rural areas during base-flow conditions. The effect of secondary treatment processes on OWC occurrence was evaluated by collecting eight samples from WWTF discharges using activated sludge and six from WWTFs samples using trickling filter treatment processes. Samples collected directly from WWTF discharges contained the largest concentrations of most OWCs in this study. Samples from trickling filter discharges had significantly larger concentrations of many OWCs (p-value<0.05) compared to samples collected from activated sludge discharges. OWC concentrations decreased significantly in samples from WWTF discharges compared to stream-water samples collected from sites greater than 2000 m downstream. Upstream from WWTF discharges, base-flow samples collected in streams draining predominantly urban watersheds had significantly larger concentrations of cumulative OWCs (p-value=0.03), caffeine (p-value=0.01), and tris(2-butoxyethyl) phosphate (p-value<0.01) than those collected downstream from more rural watersheds.     

Methylmercury in rivers draining cultivated watersheds

Total mercury (THg) concentrations in streams draining cultivated watersheds in Minnesota, USA are strongly correlated with total suspended sediment (TSS) concentrations, varying widely in response to precipitation-driven inputs of soil-derived suspended sediments. Methylmercury (MeHg) concentrations in these waterways have not been studied, and little is known about mercury uptake mechanisms in resident fish populations. To begin to identify factors influencing MeHg concentrations and loadings in these streams, we measured THg and MeHg concentrations in unfiltered whole water samples from the Minnesota River and two of its major tributaries, the Blue Earth and Le Sueur Rivers. Land use in the watersheds of these rivers is over 90% row-crop agriculture, and extensive artificial drainage systems deliver runoff and associated solids quickly to local streams and rivers. THg concentrations were elevated (>10 ng/l) during much of Spring 2000 and part of the summer when runoff from precipitation events increased stream discharge and carried soil materials into the streams. Reduced precipitation resulted in low flow conditions from August through October, and THg concentrations decreased to <4.0 ng/l in all three rivers. MeHg concentrations in the Le Sueur River ranged from 0.07 to 0.42 ng/l between June and December. Higher MeHg concentrations (>0.2 ng/l) were measured during summer months when THg and TSS concentrations were high after precipitation events. Elevated MeHg concentrations were also observed in late October after leaf litter inputs. Conditions on the Blue Earth River were different, with elevated MeHg concentrations (>0.5 ng/l) observed during low flow in August and September. These higher concentrations coincided with a period of enhanced microbial growth stimulated by high late-summer temperatures. A late-October increase in MeHg concentration attributed to leaf litter inputs was also observed in this river. MeHg concentration trends in the Minnesota River were similar to those in the Blue Earth River. Indicators of biological productivity (chlorophyll a, volatile suspended solids, and total Kjeldahl nitrogen) were higher in the Blue Earth and Minnesota Rivers compared to the Le Sueur River, which may signal a connection between higher biological activity and increased MeHg concentrations.     

Labile aluminium chemistry downstream a limestone treated lake and an acid tributary: effects of warm winters and extreme rainstorms

The outlet from the limestone treated Lake Terjevann consisted mainly of well-mixed lake water (mean pH 6.1) during the ice-free seasons including the unusually warm winters of 1992 and 1993. However, during the ice-covered period acidic water (mean pH 4.8, mean inorganic aluminium (Al(i)) about 160 microg/l) from the catchment draining under the lake ice dominated. A downstream tributary was generally acid and rich in aluminium (mean pH 4.6, Al(i) about 230 microg/l). After an extreme rainstorm loaded with sea-salts cation exchange in the soil resulted in more than a doubling of the Al(i) concentration (reaching about 500 microg/l). It took 3-4 months until the Al(i) concentration returned to pre-event levels. During the ice-covered period, the acidic outlet and tributary waters resulted in acidic conditions below the confluence (pH<4.8, Al(i) about 150 microg/l) while during the ice-free periods the more neutral outlet water resulted in higher pH and lower Al(i) concentrations (pH>5.2, Al(i) about 95 microg/l). However, during the latter climatic conditions the water was most probably more harmful to fish due to hydrolysing and polymerizing aluminium. After the sea-salt event, the increased Al(i) concentration in the tributary made the zone below the confluence potentially more toxic (pH approximately 5, Al(i) approximately 250 microg/l). Expected global warming resulting in winter mean temperatures above 0 degrees C may eliminate the seasonal acidification of the outlet from limestone-treated lakes creating permanent toxic mixing zones in the confluence below acidic aluminium-rich tributaries. Besides, more frequent rainstorms as a consequence of global warming may increase the frequency of sea-salt events and the Al(i) concentrations in the mixing zones.     

Treatment of wastewater from the meat manufacturing industry‐case study

Meat manufacturing mill wastewaters (MMM) originating from meat processing units are the most polluted wastewaters of the food industry. Discharged wastewater was characterized by high values of COD, BOD and TSS (6612, 2550 and 6220) mg/l, respectively. Moreover, the wastewater contains significant concentrations of oil and grease amounting to 4482 mg/l. Treatment processes namely, plain sedimentation, plain flotation, pressurized dissolved air flotation, chemical coagulation and biological treatment via a completely mixed activated sludge process, were chosen for this study. The results obtained revealed that plain sedimentation, column flotation and dissolved air flotation (DAF) exhibited good efficiency in removing flotation fats (93.5, 96, and 97.3%, respectively). Alum, ferrous sulfate and ferric chloride precipitation in‐combination with lime at their optimum operating conditions as minimal pre‐treatment procedures for the removal of organic matter contents exhibited good efficiency of COD, BOD, and oil and grease. The chemically treated effluent doesn't comply with the Law No.4/1994 (Egyptian Standards which regulating the discharge of industrial wastewater to the sewerage network). This is due to the high concentration of soluble organics. Activated sludge plant (ASP) with long aeration time (8hr) was suitable for the case under consideration. Results show that average residual COD, BOD, TSS and oil and grease were 270, 62, 78 and 9.8 mg/l, respectively. The biologically treated effluent is complying with Standards of discharge wastewaters to the sewerage network.     

Integrated biological and physiochemical treatment process for nitrate and fluoride removal

The feasibility of an integrated biological and physiochemical water treatment process for nitrate and fluoride removal has been evaluated. It consisted of two sequencing batch reactors (SBRs) in series. Performance of the process in the treatment of 24 synthetic water samples having nitrate concentrations of 40, 80, 120, 160, 200, and 250 mg/l (as N) and fluoride concentrations of 6, 10, 15, and 20 mg/l at different combinations was studied. Denitrification followed by defluoridation proved to be the best sequence of treatment. In all cases nitrate could be reduced to an acceptable level of less than 10 mg/l (as N) at 3, 5, and 7 h hydraulic retention times (HRTs) depending on its initial concentration. Fluoride concentrations up to 15 mg/l associated with nitrate concentrations up to 80 mg/l (as N) could be reduced acceptable 1.5 mg/l by alum-PAC slurry using alum doses up 850 mg/l [as Al2(SO4)3 x 16H2O] along with 100 mg/l of powdered activated carbon (PAC). Additional alkalinity produced during denitrification was used up during defluoridation for maintenance of pH avoiding the need for lime addition. On the other hand, residual organics, turbidity, and sulfide present in the denitrified water are removed by alum and PAC at the defluoridation stage along with fluoride, eliminating the need for an additional post-treatment step. At higher nitrate concentrations (> or = 120 mg/l as N), the alkalinity produced at the denitrification stage was in the range of 715-1175 mg/l as CaCO3. This excessive alkalinity inhibited reduction of fluoride to the level of 1.5 mg/l at the defluoridation stage, using alum doses up to 900 mg/l along with 100 mg/l of PAC. In all cases a fluoride concentration of 20 mg/l in water could not be reduced to the acceptable level of 1.5 mg/l.     

The Influence of Water-Column Mixing on Dissolved-Oxygen Concentrations and Saline Stratification in the River Tawe Barrage, Wales, UK

The Tawe barrage was an early amenity barrage, and studies after its construction showed a deterioration in water quality within the impounded area. The main concern was the effect of low dissolved-oxygen concentrations upon the migrating salmonids during their passage upstream. An aeration/mixing system was chosen in a combination of diffusers and a propeller, which has proved to be capable of maintaining satisfactory water quality. However, additional diffusers need to be installed to (a) achieve a satisfactory concentration of dissolved oxygen at all points in the river and (b) complete the full scheme.     

Characteristics and stabilities of residues from the Wheal Jane constructed wetlands

The characteristics and solubilities of residues formed during effluent treatment at the Wheal Jane constructed wetland facility in Cornwall, UK are described. The constructed wetland treats an acidic (pH 3 to 4) mine discharge enriched in iron (<100 mg/l), zinc (<80 mg/l), manganese (<20 mg/l) and arsenic (<2 mg/l). The processing strategy adopted at the site is to remove elements selectively from the mine water in distinct unit process operations and concentrate the iron and base metals into residues within the circuits. Solubility tests conducted on the materials from the aerobic and anaerobic cells attempt to simulate future possible leaching processes within landfill sites used for ultimate disposal. The tests used in the evaluation included TCLP, MARG, washing and column leaching. The aerobic solids overall have very low solubilities which are well below the TCLP thresholds for As, Cd and Pb. The TCLP results for these toxic elements are supported by the washing and column test work. The anaerobic substrates are carbonaceous in nature, composed of straw, wood pulp and manure. They contain minimal amounts of toxic compounds and are considered to be less of a disposal problem. Ochre precipitated at a pH of 3-4 in the aerobic cells contains significant concentrations of arsenic (>0.1%). This element is carcinogenic, and such residues are classified as hazardous waste under current UK landfill regulations. This classification does not take into consideration the solubility of the material but is based solely on the bulk chemical composition.     

Predicted and measured concentrations for selected pharmaceuticals in UK rivers: implications for risk assessment

Predicted environmental concentrations for five commonly used pharmaceuticals were calculated using data from the UK Department of Health according to risk assessment guidelines proposed by the European Agency for the Evaluation of Medicinal Products. Surface waters from the South-East of England were analysed and results were compared with predicted concentrations and findings from other studies from the UK and Europe. It was found that the efficacy of these predictions varied and was hampered by a shortage of data for many of the drugs. Ibuprofen, paracetamol and salbutamol were detected and quantified in all locations sampled. Ibuprofen was consistently found at the highest concentrations (up to 3 microg l(-1)). Levels up and downstream of two wastewater treatment works were compared in order to investigate the link between sewage discharge and environmental concentrations of pharmaceuticals. Results from one site demonstrated a considerable increase in concentrations of ibuprofen, salbutamol and paracetamol downstream from the treatment works; however, no link was established for a second works.     

Sorption and redox processes controlling arsenic fate and transport in a stream impacted by acid mine drainage

Reigous acid creek originating from the Carnoulès tailings impoundment supplies high concentrations of arsenic under soluble (up to approximately 4 mg/l) and particulate (up to 150 mgAs/g) phases to the Amous river, situated at the drainage basin of the Rh?ne river (Southern France). The metalloid is present as As(III) (>95%) in Reigous creek water while As(V) predominates (50-80%) in the solid phase, i.e. schwertmannite. At the confluence between acid (pH<5) creek and alkaline Amous river, As(III) concentrations decrease ten-fold through dilution and formation of As-rich ferrihydrite (As/Fe=0.02-0.1) containing 10-30% As(III). However, these attenuation processes are not efficient in the summer heatwave of 2003 since As concentrations in Amous river water (>or=20 microg/l) and As/Fe ratios in particulate matter (>or=0.07) are closed to those of Reigous creek (相似文献   

VALIDATION OF BNR (BIOLOGICAL NUTRIENT REMOVAL) PLANT

Llangefni WwTW receives discharge from the rural town of Llangefni and the local industrial estate and to date this is the first and only BNR plant in Wales. The consents from March 2003 included a reduction in ammonia (NH₄_N) to 1.5 mg/l, suspended solids to 20 mg/l (SS) and Biological Oxygen Demand (BOD) to 7 mg/l and included a new Phosphate (PO₄_P) standard of 2 mg/l. The process selected to meet the new consents was Biological Nutrient Removal (BNR) and was unusual as it was for a small, rural wastewater treatment plant that receives about 26% of its flow from an industrial estate.
During commissioning, the plant produced an average phosphate concentration of 1.0 mg/l and an ammonia concentration of 0.7 mg/l. It was confirmed that to achieve consistent phosphate removal a BOD:P ratio greater than 20:1 is required along with a high VFA (Volatile Fatty Acids) concentration of 200–300 mg/l.     

Biogeochemical behavior of organic carbon in the Trinity River downstream of a large reservoir lake in Texas, USA

Dissolved and particulate organic carbon concentrations were measured and annual loads estimated for the Trinity River, the main freshwater input source to Galveston Bay, which lies on the upper Gulf coast of Texas, USA, during 2000-2001. This river drains the forested lowlands south of a relatively large reservoir lake, Lake Livingston. A weak relationship between dissolved organic carbon (DOC) and Q(TR) indicated hydrologic control but separation of the data, based on individual discharge events, was necessary to improve interpretation. For instance, the first rain of the season resulted in only a modest increase in DOC concentrations and led to an inverse relationship with discharge, due to decreased lateral flow and increased infiltration of rainwater, with the lower flows being more efficient at DOC leaching from soils. In contrast, a long duration high discharge river crest event resulted in an opposite trend, i.e. a linear increase in DOC with increasing discharge rates. A short duration high discharge tropical storm showed reduced Trinity River DOC concentrations and the highest POC concentrations measured, likely resulting from the relatively short duration, and minimal contact time, of this event. In contrast to DOC, the concentrations of particulate organic carbon, POC (mg C l(-1)) were linearly correlated to suspended particulate matter (SPM) concentrations and accounted for between 10 and 12% of the total suspended load at low discharge but decreased to approximately 2% at high discharge. This suggests dilution by larger particles with a reduced organic carbon content, possibly silicate minerals, more readily resuspended at elevated levels of discharge. The annual total organic carbon (TOC) load to Galveston Bay, estimated from the slope of the daily load vs. discharge relationship, was 11.2 x 10(10) g C and calculated export coefficients (g C m(-2) year(-1)) were in good agreement with previous results. Using this relationship, accurate assessments of TOC flux inputs to Galveston Bay over the past quarter-century and in the future are possible by obtaining annual Trinity River discharge rates, which are readily available from the USGS. Comparing DOC riverine inputs to benthic sources in Trinity Bay, measured directly on the same day, indicates that the sediments contribute approximately 20% of total inputs of DOC to Trinity Bay. However, assuming a constant benthic source during low-flow conditions, which can occur for periods of up to 14 months in this region of Texas, benthic fluxes would account for > 80% of the total inputs into Trinity Bay. At high levels of discharge, the Trinity River discharges approximately 1.0 x 10(9) g C day(-1) and dominates DOC inputs to Trinity Bay.     

Arsenic Removal from Water Supplies in Northern Chile Using Ferric Chloride Coagulation

Many raw waters in the arid North of Chile contain high concentrations of arsenic (0.1–1.0 mg/l) and, during the 1970s, drinking-water treatment using coagulation was introduced in an attempt to comply with the Chilean standard of 0.05 mg/l. The new World Health Organization recommendation of 0.01 mg/1 for drinking water has led to efforts to enhance arsenic removal.
This paper describes pilot-plant experiments which were carried out to optimize removal by varying the ferric chloride coagulant dose (3–9 mg/1 Fe) and pH value (pH 5.5–8.0) in a raw water which contained an average arsenic concentration of 0.44 mg/l. At pH 5.5, arsenic adsorption was best; however, a pH of 6.5 was considered to be the most suitable for treatment when considering floc elimination. An empirical formula to predict residual arsenic under different operational conditions was obtained and this was confirmed by data collected at a full-scale water-treatment plant.     

Discharge of methylmercury-enriched hypolimnetic water from a stratified reservoir

A study conducted from July 1995 to June 1996 examining spatial and temporal distribution of mercury (Hg) at the Caballo Reservoir, New Mexico, revealed that the highest levels of methylmercury (MMHg) occurred in both the inlet and the Rio Grande upstream of the reservoir. As a result, a second study was designed to identify possible sources of the elevated levels of MMHg, and to determine if water discharged from the Elephant Butte Reservoir upstream could be a primary source. In July 1996, as anoxia began to develop in the hypolimnion of the Elephant Butte Reservoir, surface water MMHg concentrations were below the MDL of 0.018 ng/l while water discharged into the tailrace was 0.149 ng/l MMHg. By September 1996, when the anoxic hypolimnion spanned 60% of the total reservoir depth, surface water MMHg was still below the MDL, while discharge water had increased to 1.144 ng/l MMHg. Following reservoir turnover in November 1996, surface water increased to 0.264 ng/l MMHg while discharge water decreased to 0.420 ng/l MMHg. By January 1997, MMHg in the tailrace decreased to pre-stratification levels, and both surface water and discharge water reached similar MMHg levels until the onset of summer stratification in July 1997. This trend was repeated the following year when MMHg concentrations in the tailrace increased from 0.190 ng/l in August 1997 to 1.240 ng/l in September 1997. In addition, vertical profile sampling of the reservoir from August 1997 to September 1997 showed a buildup of MMHg in the anoxic hypolimnion which coincided with increasing levels of MMHg discharged into the tailrace. During the course of this study the single largest contribution of MMHg to the river below the reservoir was from water released through the dam during the fall months of the year.     

Biodegradation kinetics of Methylosinus trichosporium OB3b at low concentrations of chloroform in the presence and absence of enzyme competition by methane

The kinetics of chloroform and trichloroethylene (TCE) degradation by the methanotroph, Methylosinus trichosporium OB3b, were measured in batch kinetic experiments. The experiments focused on initial concentrations of around 100 μg/l for chloroform and around 1 mg/l for TCE. The pseudo first-order rate constants ranged from 0.2 to 0.41/mg TSS-day for chloroform and from 0.5 to 3.31/mg TSS-day for TCE in the absence of methane. Comparison of the TCE rate constants to other work indicates that the organisms were producing the soluble form of their methane monooxygenase. The presence of methane caused significant enzyme competition at methane concentrations as low as 0.35 mg/l, resulting in smaller chloroform rate constants. The decreases in the rate constant were consistent with the predictions of an enzyme competitive inhibition model, which indicated a half saturation coefficient for methane in the order of 0.3 mg/l. The predominant degradation products from chloroform was carbon dioxide.