scholarly journals A colony count model for the control of drinking water distribution systems

2005 ◽  
Vol 9 (2) ◽  
pp. 189-205
Author(s):  
A. Kerneis ◽  
A. Déguin ◽  
M. Feinberg
Keyword(s):  
Organic Matter ◽  
Process Control ◽  
Residence Time ◽  
Distribution Systems ◽  
Control Parameter ◽  
Control Parameters ◽  
Supply Water ◽  
Biodegradable Organic Matter

The purpose of this study is to select a process control parameter for monitoring microbial regrowth in a network and to develop a more accurate and relevant quality control of supply water. Two parameters were examined as potential process control parameters: the water residence time in the network and the concentration of biodegradable organic matter. Residence time calculations were carried out and validated by tracer studies in a branched network and then in a simply looped network. The measurement of the natural dissolved organic carbon (DOC) consumption in the network was preferred to the determination of any in vitro biodegradation. The measurement of consumption requires the determination of DOC in treated water and in supply water. It is simpler and less expensive than other biodegradable organic matter determinations. A model for colony counts as a function of the residence time was developed in order to demonstrate that this parameter can be used for process controlling. This model was very well adjusted to data collected in a network in winter, spring and summer. This process control parameter was then used in order to locate and estimate the quantity of water whose colony counts exceed the European directive guide level. Accurate correlation measurements between colony counts and DOC consumed in the network were carried out in three distinct systems. No significant correlations were measured. For these three networks, biodegradable organic matter measurements based on DOC determinations were demonstrated to be unreliable process control parameters for monitoring bacterial regrowth.

A MODIFIED METHOD FOR THE IN VITRO DETERMINATION OF DRY MATTER AND ORGANIC MATTER DIGESTIBILITY

1973 ◽  
Vol 53 (2) ◽  
pp. 251-256 ◽  
Author(s):  
R. E. LARSEN ◽  
G. M. JONES
Keyword(s):  
Organic Matter ◽  
Dry Matter ◽  
In Vitro Fermentation ◽  
Modified Method ◽  
Initial Stage ◽  
Fermentation Period ◽  
Organic Matter Digestibility ◽  
Stage 1

Several modifications were made to the two-stage in vitro fermentation techniques for dry matter and organic matter digestibility (IVDMD and IVOMD) determinations developed by Tilley and Terry (J. Brit. Grassland Soc. 18: 104–111, 1963) and Alexander and McGowan (J. Brit. Grassland Soc. 21: 140–147, 1966). These modifications included: (1) changing the buffer medium, which resulted in a pH of 6.8–7.0 in the fermentation tubes during the initial (stage 1) 48-h fermentation period, and (2) shortening the acid-pepsin incubation period from 48 to 24 h, and thus reducing time for estimation of both IVDMD and IVOMD by 24 h. Modification (1) eliminated pH adjustments during fermentation and acidification at the end of the fermentation period. Acid-pepsin digestion of substrates was completed within 24 h instead of 48 h. Both IVDMD and IVOMD values were obtained on the same substrates. These modifications were evaluated using 65 samples that arose from 13 forages, comprised of corn and grass silages and their mixtures, which had been dried by five different methods. IVDMD and IVOMD were determined on all samples, comparing the modified method with the parent methods. IVDMD and IVOMD coefficients within each method were not statistically different between the Tilley and Terry method and the modified method.

EFFECTS OF DIFFERENT DRY MATTER DETERMINATION METHODS ON CHEMICAL COMPOSITION AND IN VITRO DIGESTIBILITY OF SILAGES

1973 ◽  
Vol 53 (4) ◽  
pp. 753-760 ◽  
Author(s):  
R. E. LARSEN ◽  
G. M. JONES
Keyword(s):  
Organic Matter ◽  
Crude Protein ◽  
Dry Matter ◽  
In Vitro Digestibility ◽  
Cellulose Content ◽  
Freeze Dried ◽  
Gross Energy ◽  
Determination Methods

Dry matter (DM) contents of 13 silages, comprised of 5 corn, 4 legume–grass, and 4 corn–hay crop silage mixtures, were determined by (1) toluene distillation (TD), corrected for volatiles lost into the aqueous distillate; (2) TD, uncorrected; (3) freeze-drying (FD); (4) oven-drying (OD) at 40 C; (5) OD at 65 C; and (6) moisture-tester at 100 C. Corrected TD showed significantly higher (P < 0.01) DM levels compared with other methods. Up to 12.8% loss of DM resulted from heat-drying, depending on the method and the sample. Dried-ground silages were analyzed for nutrient composition. No significant changes in cell-wall constituents or organic matter contents were observed. Silages that were FD were highest in cellulose content (P < 0.05), whereas both FD and OD at 40 C resulted in significant increases in gross energy (P < 0.05) and crude protein (P < 0.01) content compared with other methods. FD or OD at 40 C resulted in the highest dry matter solubility and in vitro digestibility of cellulose, dry matter, and organic matter (P < 0.05). The lowest values for these analyses were obtained with silages heat-dried at 65 and 100 C. Results of these studies suggest that corrected TD should be used for determination of silage DM content and that in vitro analyses or other biochemical determinations should be conducted on silage samples that have been freeze-dried or oven-dried at 40 C.

Comparing estimates of herbage digestibility from faecal nitrogen and in vitro determinations

1980 ◽  
Vol 31 (1) ◽  
pp. 57-62
Author(s):  
H. A. Birrell
Keyword(s):  
Organic Matter ◽  
Digestible Organic Matter ◽  
Faecal Nitrogen ◽  
Feeding Trials ◽  
Grazing Sheep ◽  
Organic Matter Digestibility ◽  
Image Position ◽  
Stocking Rates

ABSTRACTIn a grazing experiment, the organic matter digestibility of herbage selected by sheep grazing at two stocking rates was determined at monthly intervals over a 9-month period by (i) the in vitro determination of organic matter digestibility of the material collected from sheep fitted with an oesophageal fistula, and (ii) derivation from the prediction of digestible organic matter intake with a faecal nitrogen regression. A comparison of the two techniques confirms the view of other workers that faecal nitrogen indices based on pen feeding trials of green herbage are unreliable for predicting digestibility of green herbage in the field. The bias which is produced by faecal nitrogen regression appears to be associated with the time spent grazing by the animal each day. Relating organic matter digestibility directly to nitrogen content of faeces of grazing sheep (N, g nitrogen/100 g faecal organic matter) and their grazing time (T,h) yielded the following equation:The expression has standard errors (±2·6) similar to those involved in an in vitro determination. It provides a simple technique for estimating digestibility of herbage eaten by grazing sheep, but this may only be applicable to the particular sward conditions.Field estimates of digestibility over summer and autumn by this equation were found to be similar to estimates by a faecal nitrogen expression established from hand feeding sheep with dry summer herbage.

Caractéristiques isotopiques (18O, 13CO2, 3H) des écoulements dans une tourbière sur pergélisol au Nouveau-Québec

1982 ◽  
Vol 19 (6) ◽  
pp. 1255-1263 ◽  
Author(s):  
Laurent Dever ◽  
Michelle Laithier ◽  
Claude Hillaire-Marcel
Keyword(s):  
Organic Matter ◽  
Water Flow ◽  
Residence Time ◽  
Lag Time ◽  
Temperature Relationship ◽  
Mean Annual Temperature ◽  
Hydraulic Characteristics ◽  
A Value ◽  
Winter Snow

The 18O – mean annual temperature relationship, which is known in organic matter, presents some anomalies in Sphagnum. A study of water flow and isotopic characteristics of an arctic mire (Leaf River, Ungava Peninsula) has been undertaken to explain these anomalies. The isotopic compositions of the water (18O, 13CO2, 3H) permit the determination of some hydraulic characteristics of a peat on permafrost: (1) evaluation of the lag time between a rainfall and the discharge; (2) evaluation of the residence time of the water; and (3) subsequent mixing parts. A relationship between the isotopic characteristics and the ombrotrophic or minerotrophic nature of the mire is observed. A δ18O value of −11‰ appears in the ombrotrophic zone and a value of −17‰ in the minerotrophic zone. The relative enrichment in 18O of the first one indicates a shorter residence time. The isotopic changes subsequent to rainfalls (with δ18O = −12.2, −14.5, and −19.1‰ differ in time and space: (1) a 2‰ change is observed within 24 h in the minerotrophic zone; (2) a 6‰ change appears almost instantaneously in the ombrotrophic zone. 3H values indicate that neither the meltwater from winter snow (with low 3H content), nor the meltwater from permafrost participates in the subsurface flow.

Impacts of the Reduction of Nutrient Levels on Bacterial Water Quality in Distribution Systems

1999 ◽  
Vol 65 (11) ◽  
pp. 4957-4966 ◽  
Author(s):  
Christian J. Volk ◽  
Mark W. LeChevallier
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Organic Carbon ◽  
Biological Treatment ◽  
Distribution Systems ◽  
Model Systems ◽  
Biological Filtration ◽  
Nutrient Levels ◽  
Bacterial Concentrations ◽  
Biodegradable Organic Matter

ABSTRACT This study evaluated the impacts of reducing nutrient levels on bacterial water quality in drinking water. Two American Water System facilities (sites NJ102a and IN610) with histories of coliform problems were involved, and each water utility received two pilot distribution systems (annular reactors). One reactor simulated the conventional treatment conditions (control), while the other reactor was used to assess the effect of biological filtration and subsequent reduced biodegradable organic matter levels on suspended (water column) and biofilm bacterial concentrations in the distribution systems. Biodegradable organic matter levels were reduced approximately by half after biological treatment. For site NJ102a, the geometric mean of the assimilable organic carbon concentrations was 217 μg/liter in the plant effluent and 91 μg/liter after biological filtration. For both sites, plant effluent biodegradable dissolved organic carbon levels averaged 0.45 mg/liter, versus 0.19 to 0.22 mg/liter following biological treatment. Biological treatment improved the stability of free chlorine residuals, while it had little effect on chloramine consumption patterns. High bacterial levels from the biological filters resulted in higher bacterial concentrations entering the test reactors than entering the control reactors. On average, biofilms in the model systems were reduced by 1 log unit (from 1.4 × 105 to 1.4 × 104 CFU/cm2) and 0.5-log unit (from 2.7 × 105 to 7.8 × 104CFU/cm2) by biological treatment at sites NJ102a and IN610, respectively. Interestingly, it required several months of biological treatment before there was an observable impact on bacterial water quality in the system, suggesting that the effect of the treatment change was influenced by other factors (i.e., pipe conditions or disinfection, etc.).

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