Tested Water Samples Research Articles

Comparison of decontamination methods for the isolation of mycobacteria from drinking water samples

Cetylpyridinium chloride (CPC), sodium hydroxide (NaOH) and formaldehyde (HCHO) were compared for their efficacy as decontamination substances for the isolation of mycobacteria from drinking water samples. For this purpose pure cultures of nine mycobacterial strains and four strains of potential contaminants were tested for their sensitivity to CPC (0.001, 0.003, 0.005%), NaOH (0.5, 1.0%) and HCHO (0.1, 0.5, 1.0%). The results of these tests are given in terms of decimal reduction times. Additionally, 36 drinking water samples were processed using the following six decontamination methods: (i) CPC, 0.001%, 30 min; (ii) CPC, 0.005%, 30 min; (iii) NaOH, 0.5%, 30 min; (iv) NaOH, 1.0%, 30 min; (v) HCHO, 0.1%, 60 min; (vi) HCHO, 0.5%, 60 min. In this field study method ii proved to be the most effective procedure resulting in the highest isolation (64%) and lowest contamination rate (11%). Method iii may be useful when testing water samples for Mycobacterium chelonae and M. fortuitum and if high concentrations of red pigmented contaminants resistant to CPC are to be expeected. Methods v and vi were not found to be suitable for decontamination.

An Evaluation Of Corrosion Monitoring Techniques For Measuring Corrosion Inhibitor Performance In Sour Gas Gathering Systems

Abstract Amoco Canada Petroleum Ltd. operates approximately 50 sour gas wells in the Fox Creek area of Alberta. Historically, anodic polarization probes and corrosion inhibitor residual measurements have been utilized to monitor corrosion inhibitor performance and to verify system inhibition. In this study, a wellhead test loop was installed to compare various corrosion monitoring techniques and to determine the effectiveness and cost performance of several new corrosion inhibitors. Anodic polarization was useful for measuring relative corrosion rates and relative inhibitor performance. In view of the differences observed between anodic polarization measurements and corrosion coupons, the former technique should be used in conjunction with corrosion coupons, particularly when evaluating new corrosion inhibitors. In the test protocol, electric resistance probes were not useful for short-term inhibitor evaluation, although they warrant further investigation as a long-term monitoring technique in systems where the inhibition criteria have been previously established. The hydrogen probe was not sensitive or responsive to changes in corrosion inhibitors, or inhibitor injection rates. Although the exposure time of the corrosion coupons was typically six to eight days, the polished rod coupons provided valuable metallurgical response to the various inhibitors tested. Finally, corrosion inhibitor residuals were useful for verification of inhibitor injection rates and correlated well with the optimum concentrations determined by laboratory studies. Introduction Corrosion History Production from the Kaybob South Beaverhill Lake gas field began in 1968, with initial projections for low water production. However, severe water coning occurred immediately and water production rates were much higher than originally anticipated. As the water rates increased, so did the chloride content of the produced water. The combination of these two factors resulted in several internal corrosion problems. The resulting failures were caused by isolated pitting attack in the bottom quadrant of the pipeline in low velocity areas, and in low elevation areas where produced fluids accumulated. The design of the gas gathering system precluded any form of pigging or detailed line inspection using smart pigs. Consequently, the development of an effective water soluble or highly water dispersible corrosion inhibitor was required to control internal corrosion in the gas gathering system. Initially, control of the chemical injection program was extremely difficult due to two factors a continually increasing water production rate and infrequent well testing, as well as limited access points for obtaining water samples for inhibitor residual testing. Line failures continued to be a problem until an extensive testing program was initiated, which provided the information required to predict and set maximum flow rates to stabilize water production. A water soluble/dispersible inhibitor was developed during the same period and the combination of these two factors resulted in the successful control of internal corrosion problems in the Kaybob South gas gathering system. Throughout the life of the field, the following factors have significantly contributed to the development of a successful corrosion inhibition program.Extensive well testing allowed ongoing monitoring and projection of water production rates.The development of a corrosion inhibitor which exhibited significant water solubility dispensability.

Efficacy of chemical dosing methods for isolating nontuberculous mycobacteria from water supplies of dialysis centers.

Investigations of nontuberculous mycobacterium (NTM) infections associated with various environmental sources have been hampered by the lack of adequate techniques for selective isolation of these organisms from environmental fluids. This study compared chemical dosing techniques for recovery of NTM from water samples collected from 115 randomly selected dialysis centers. Cell suspensions of NTM group II and IV isolates and gram-negative bacteria were exposed to solutions containing sodium hypochlorite (0.2 micrograms/ml of free available chlorine), formaldehyde (1, 0.75, or 0.5%), oxalic acid (1.25%), cetylpyridinium chloride (25 micrograms/ml), or cetyltrimethylammonium bromide (100 micrograms/ml). Results of standard membrane filtration assays with laboratory test strains and water samples from dialysis centers showed that 5 min of exposure to 1% formaldehyde effectively reduced gram-negative bacterial populations and allowed increased recovery of NTM in environmental fluids containing mixed microbial populations.

Limitations of the A-IM Method for Fecal Coliform Enumeration in the Pacific Oyster (Crassostrea gigas)

Use of the A-1M method, which was originally devised for testing water samples, has recently been extended for enumeration of fecal coliforms and Escherichia coli in shellfish and other food products. Results of our study indicate that while this method is reliable for analysis of growing waters, the use of the A-1M method for testing Pacific oysters may be less reliable because bacteria not belonging to the coliform group but which are sometimes present in these animals also give a positive reaction.

Influence of agricultural practices on nitrates in the water table aquifer

Water samples for nitrate testing were collected from over 200 wells in Kent and Sussex counties in Delaware over an 18-month period in areas with different agricultural land use. Nearly 70% of the wells were individual home water supplies. The rest of the wells, constructed from 3·2-cm diameter PVC pipe, were installed at selected locations. Water samples were also collected from monitoring wells around two potato-growing sites, on irrigated corn and soybean areas, a field spread with poultry manure, two animal-waste lagoon sites, and near stockpiled poultry manure. Certain agricultural activities cause higher nitrate concentrations in the ground water. Poultry manure has increased nitrate concentrations in the ground water in southern Delaware more than commercial fertilizer. Highest nitrate concentrations are found in areas with excessively well-drained soils. Some clay-lined, animal-waste lagoons may cause ground-water contamination. Potato growing in Delaware is not causing high nitrate concentrations in the water table aquifer because of the heavier soils that are not as susceptible to nitrite leaching.

Invertebrate bioassays with North Sea water samples. I. Structural effects on embryos and larvae of serpulids, oysters and sea urchins

Structural effects of bottom and surface water samples from two dumping grounds in the inner German Bight on the development of three meroplanktonic organisms(Pomatoceros triqueter: Polychaeta,Psammechinus miliaris: Echinodermata andCrassostrea gigas, Mollusca) were investigated. The titaniumdioxide dumping site was sampled immediately after dumping (within the visible waste trail 1 km behind the vessel), and 10 h after dumping. Samples were taken in the sewage sludge deposition area in the intervals between the usual dumping activities, regardless of the exact dumping schedule. The preserved bioassay test organisms were inspected microscopically to count percentages of “normal” larval hatch in test water samples, reference water samples and laboratory aged control water samples (5 to 10 replicates). The relative water quality at various dumping sites was expressed in terms of “net risk”-values (Woelke, 1972) compared to hatching rates observed in the controls. Larval development ofP. triqueter was significantly suppressed (up to −22 % “net risk”) in trail water of the titanium dioxide dump site while the development of sea urchin larvae was still affected in the 10 h surface samples. Hatching of all test organisms in bottom-water samples from the centre of the sewage sludge dump site was affected to different degrees when compared to reference areas about 4 km north or 6 km northwest of the dumping area. The general usefulness of standardized bioassay procedures in pollution monitoring programmes is discussed. The results presented here call for further verification to minimize experimental background variability and to enlarge the catalogue of suitable effects criteria.

Hydrology and chemistry of surface and groundwater resources of the Aguata area, SE Nigeria

The project area is underlain by two Tertiary sedimentary rock sequences, i.e. the Imo and the Ameki Formation. The Imo shales generally occupies the Eastern lowlands, with patches of relatively resistant crust of laterite and ironstone forming rounded to sub-rounded, oval-shaped hills and small ridges often standing above the general ground level. The elevations vary from 92 to 166 m. One outstanding feature of the study area is the N-S trending escarpment, underlain by the Nanka Sands of Ameki Formation. The cuesta which attains its maximum altitude of about 366 m at Igbo-Ukwu forms the Western Upland with gullies of variable magnitude deeply incised at different locations along the scarp fronts. The soil erosion is, on the whole, very active and devastating, especially along the eastern slopes.The map area is drained by the Aghomili river system. The western tributaries of this river run parallel to one another. The headwaters forming the drainage pattern emerge as numerous groundwater effluents, generally with small yields. The low discharge is thought to be due to the direction of flow being opposite in character to the dip of the sand beds—obsequent discharges.The Aguata area, on basis of lithology, is split into two hydrogeologic provinces, namely the eastern region with fairly high density of rivers, streams, springs and lakes, and the western region generally devoid of these surface water bodies. Whereas most of the eastern district appears to have adequate sources of surface water and commonly lacks good ground water potentials, the western region (Western Upland) is rich in ground water but generally is deficient in surface water. Surface water can only be found at the lower eastern slope of the cuesta and to the southwest of the town of Uga. The towns and villages located in this area (the cuesta zone) experience acute water shortage. Information of boreholes from adjacent areas show that the depth of water table of the Nanka Sands varies from 93 m at the St. Joseph's Hospital compound at Adazi to 264 m at Igbo-Ukwu. The Imo Shale environment contains several thin aquifers with water seepages issuing at different horizons.Most of the tested water samples are wholesome, springs are clear and colourless, but streams, rivers, etc. are, more often than not, turbid because of sediments and organic matters in suspension. pH range 5.2–6.8 and TDS of 24–112 ppm classifies the sampled streams, rivers, etc. as almost meteoric water. All the water samples are characteristically low in total dissolved solids (TDS) and ostensibly in specific conductance. Coliform count test suggested that coliform organisms lie between 25 and 900 per 100 ml. This range is considered too high for potable water. However, the physical and chemical test produced water with properties generally satisfactory for most domestic and industrial vantages.

An Evaluation of the Need for Preserving Potable Water Samples for Nitrate Testing

An evaluation of literature related to possible changes in water nitrate content indicates that substantial changes in nitrate content for water of potable quality are unlikely. This hypothesis is verified by a nitrate sample preservation study.

Solubilization of biologically available phosphorus by autoclaving Selenastrum

SummaryAutoclaving solubilized 70–85% of the P contained in Selenastrum but only 15–45% appeared as soluble reactive P (SRP) (Tables 1 and 4). The soluble but non-reactive phosphate (TSP minus SRP) was generally not available for cell replication in 21 days in the Algal Assay Procedure: Bottle Test (U.S.E.P.A., 1971), but there were some exceptions in which a portion of this fraction was used. SRP was consistently available in the 21-day Bottle Test. Retardation of growth rate due to removal of essential micronutrient(s) other than iron was observed when the cell population at the time of autoclaving was sufficiently high. Recently acquired surplus P was released as SRP in greater yield (~ 50%) by autoclaving than older surplus P.The nutritional state of the algae present in Bottle Test water samples influences the test results and must be considered in their interpretation.