APHA Standard Methods Research Articles

Assessment of Water Quality of Gurara Water Transfer from Gurara Dam to Lower Usuma Dam for Abuja Water Supply, FCT, Nigeria

Water transfer from area of excess to area of scarcity is now becoming accepted option especially for regional water supply. The Gurara water transfer provides for the transfer of raw water from Gurara dam in Kaduna state to Lower Usuma dam in Federal Capital Territory (FCT), Abuja through a 75Km conduit pipeline to augment water supply to FCT as a result of rapid population growth. The purpose of the research is to provide baseline condition in term of quality of raw water at Gurara dam before the transfer and after mixing at Lower Usuma dam. Water Quality Index (WQI) was used to assess the quality of the waters for overall, drinking, aquatic, recreation, irrigation and livestock uses. Twenty (20) water samples from both dams were collected and some at predetermined depths and subjected to physicochemical analysis using APHA standard methods of analysis for both wet and dry seasons. The overall WQI was poor. The WQI was poor for drinking and aquatic, but fair for recreation and livestock, and good for irrigation. These were due to high concentration of COD, BOD, total hardness, turbidity, Ca<SUP>2+</SUP>, K<SUP>+</SUP>, Mg<SUP>2+</SUP>, Cd<SUP>+</SUP>, Pb<SUP>+</SUP> and Fe<SUP>2+</SUP>. The results of the analysis when compared with the Nigerian Standard for Drinking Water Quality (NIS 544:2007) and World Health Organization (WHO) permissible limits showed that the Gurara dam and Lower Usuma dam were polluted and that the water was not safe for drinking. Variations in the constituents’ concentration in terms of water depths and seasons were observed. Regular monitoring of the water quality should be carried out as the watershed is presently rural but faces potential urbanization in the coming decades.

QUALIDADE DA ÁGUA SUBTERRÂNEA PARA CONSUMO HUMANO E USO AGRÍCOLA NO SUL DO ESTADO DO ESPÍRITO SANTO

Water quality assessment is needed for ensure sustainable and safe use for drinking, farming and industrial purposes. The aim of this work was to analyze groundwater quality in the countryside of Alegre County, located in the Southern part of Espírito Santo State, which represents a typical example of small farms in the interior of Brazil. Standard methods of APHA were used to analyze water samples from 60 wells. Parameters that influence water quality for drinking and farming purposes were determined and compared with legal thresholds. Values of turbidity, pH, iron and thermo-tolerant coliforms were above permitted limits for drinking purposes of Brazilian Health Ministry´s regulation. It was not identified any problem in water quality for irrigation relating to salinity content, however, it is not recommended the use of this water for irrigation of vegetables that are raw consumed due the presence of thermo-tolerant coliforms.

Evaluation of the Level and Impact of Selected Physiochemical Parameters of Fertilizer Effluent on Obinna River, Adani, Enugu State, Nigeria

This work quantitatively evaluates the level and impact of selected physiochemical properties of fertilizer effluent on the Obinna River of Adani, Enugu State, Nigeria. The fertilizer effluent originated from surrounding farms and flushed into the Obinna River. Water samples were collected from designated points along the river and analysed for physical, chemical and biological properties using standard methods of APHA. Impact of selected key parameters such as nitrate, phosphate, manganese, dissolved oxygen, biochemical oxygen demand and heavy metals (lead, iron and manganese), was studied. The results of the parameters were compared with the World Health Organisation (WHO) permissible standard for freshwater. Measured concentrations of phosphate (5.00, 7.21, 3.92 mg/L), manganese (1.53, 1.18, 1.47 mg/L) and lead (18.9, 21.7, 39.7 ppm) were found to be above the WHO standard while nitrate (0.04, 0.03, 0.03 mg/L) and iron (0.001, 0.001, 0.1 mg/L) were within the standard. The mean concentrations of heavy metals increased in the following order: Fe (0.034) 1 to downstream S3, with manganese and lead being above WHO standard. The results showed a level of significance for the chi-square distribution and correlation coefficients while the analysis of variance (ANOVA) results was conflicting. It could be inferred that the impact of the selected parameters contributed to the pollution of Obinna River.

Comparative Analyses of Levels of Some Trace Metals in Boreholes and Hand-Dug Wells Water Sources Within and Around Lafia Metropolis

In this study, the levels of some trace metals (As, Co, Cr, Cd, Pb, Al, Ni and Mn) were determined in boreholes and hand-dug well water sources in Lafia town and its environs using Atomic Absorption Spectrophotometry (AAS). Sampling, preservation of the water samples, pre-concentration and analyses of the trace metals were carried out as prescribed by APHA, AWWA, and WEF Standard Methods for the Examination of Water and Waste Water. In the wet season(WS), the highest mean concentrations(mg/L) of trace metals from boreholes (BH) was Mn(0.7787 +0.2389) in Lafia West while the least was Pb(0.0049 +0.0001) in Lafia South. Similarly for hand -dug wells (HDW) in wet season, the highest was Mn(0.6227 + 0.0260) in Lafia West while the least was As(0.0106 + 0.0001) in Lafia East. In dry season(DS), the highest mean concentration of trace metals from BH was Mn(0.3815 + 0.0907) in Lafia West while the least was Cr(0.0042 + 0.0001) in Lafia South. Similarly for HDW in dry season, the highest was Mn(0.3588 + 0.0762) in Lafia West while the least was Ni(0.0065+0.0001) in Lafia Central. However Cd and Al were not detected within the two seasons. In all, the analyses revealed the presence of 40%As, 40%Co, 37.5%Cr, 25%Pb, 25%Ni and 97.5%Mn from the total ground water samples. Their mean concentrations were compared with standards of a number of regulatory bodies such as World Health Organization (WHO), National Agency for Food Drug and Control (NAFDAC), National Standard for Drinking Water Quality (NSDWQ for Borehole). In comparison, the results showed higher levels of these metals than the maximum tolerable limits, particularly those of As(0.2710+0.0001 - 0.0106+0.0001), Co (0.2406+0.2114-0.0281+0.0001), Cr(0.5049+0.5871-0.0272+0.0001) for all the water samples throughout the seasons. However those of Pb(0.0423+0.0537-0.0049+0.0001),Ni(0.3729+0.0001- 0.0841+0.0001),Mn(0.7787+0.2329-0.1049+0.0322) were within tolerable limits in most cases. The results indicate that these ground water sources were polluted more prominently in wet season; BH (WS)>HDW(WS)>BH(DS)>HDW(DS) in all locations, with specific reference to As, Pb, because of their high toxicities and therefore not safe for drinking.

Evaluation of quality of air, water and noise in Gwalior, Madhya Pradesh (India)

PurposeThe first approach mainly aims at measurement of SPM, SO2 and NO2 from different sources in the Gwalior region and the second and third approach aims at the quantification of water and noise quality of the city of Gwalior. The purpose of this paper is to discuss these approaches.Design/methodology/approachThe water analysis was carried out by the standard methods of APHA, 2005 and the air and noise analysis were carried out by the standard procedures of CPCB, New Delhi and published work earlier respectively.FindingsThe water quality in the city was well within the standards, however, the noise and air quality in the city was above the standards set by CPCB, New Delhi.Originality/valueThis is the first approach in the city of Gwalior that related air pollution, water pollution and noise pollution to acute and chronic illnesses amongst all age groups. This will lead to the development of a sustainable city, while working to transform the city of Gwalior into a sustainable city.

Dispersive liquid–liquid microextraction combined with microvolume spectrophotometry to turn green the 5530 APHA standard method for determining phenols in water and wastewater

In this work, a new method based on the combination of dispersive liquid–liquid microextraction (DLLME) with microvolume spectrophotometry has been developed as a greener and miniaturized alternative to the 5530 APHA standard method for determining phenols in water and wastewater. The method relies on the oxidative coupling of phenols with 4-aminoantipyrine (4-AAP). In order to preconcentrate the dye formed, the classical liquid–liquid extraction used in the 5530 APHA method (involving 500mL of sample and 50mL of trichloromethane) has been replaced by DLLME (with 5mL of sample, 50μL of trichloromethane and 200μL of acetonitrile). After optimization, the method yielded limits of detection and quantification (0.8 and 2.5μgL−1, respectively) that were comparable with those obtained by the 5530 APHA standard method. Repeatability, expressed as relative standard deviation, was 5.2% (N=6), and the enrichment factor (EF) was 700. The proposed method was applied to the determination of phenols in different water samples and a wastewater with recoveries in the range 90–99%. The greenness profile was established in accordance with the suggestions made by the NEMI (National Environmental Methods Index). The absence of PBT (persistent bioaccumulative and toxic chemicals) and corrosive reagents and a drastic reduction of generated wastes can be emphasized.

Development of a Low-Cost SIA-Based Analyser for Water Samples

An automated multiparametric water analyser was developed and evaluated. The system was based on Sequential Injection Analysis and featured a photometric detection system comprising a tricolour RGB LED source and a photodiode. A program compiled in Visual Basic was used to control the SIA flow system, the LEDs, and the data acquisition and processing. The program loads and executes methods written in ASCII and stored as text files. The system was capable of handling up to four methods simultaneously. When used to carry out methods based on the APHA standard methods, the figures of merit obtained were considered satisfactory for the purpose. The total cost was under US $4600. It was concluded that the analyser is appropriate for routine use and has potential for an increased number of simultaneous methods and for enhanced capabilities if new versions of the software are developed.

Assessment of the Water Quality Index of Otamiri and Oramiriukwa Rivers

Problem statement: The impact of anthropogenic activities on Otamiri and Oramiriukwa Rivers as a result of the increasing rate of urbanization in Owerri, Nigeria is of a great concern due to the fact that water from these rivers is the source of water distributed for public use. These rivers are of particular importance in the study of surface water pollution because effluents from industries, municipal waste, agricultural and urban run-off are discharged into it thereby deteriorating the quality. Approach: This study used the application of Water Quality Index (WQI) in evaluating the quality of Otamiri and Oramiriukwa Rivers for public usage. This was done by subjecting the 180 samples collected to comprehensive physicochemical and bacteriological analysis using APHA standard methods of analysis. Results: The overall WQI for the samples was 174.49. The high concentration of conductivity, color, total solids, turbidity, total coliform, iron, manganese, COD, BOD and nitrate were responsible for the high value of WQI which may be attributed to the anthropogenic interference along the river bank. The results of the analysis when compared with the Nigerian Standard for Drinking Water Quality (NSDWQ) permissible limit showed that the rivers were polluted and that the water is not safe for domestic use and would need treatment. Conclusion: The use of WQI in elucidating surface water quality evaluation and management has been demonstrated by this study. WQI is also valuable tool in categorizing the pollution sources of surface waters.

Evaluation of water quality index and its impact on the quality of life in an industrial area in Bangalore, South India

Groundwater is an essential and vital component of our life support system. The deterioration in the groundwater quality due to geogenic and anthropogenic activities has drawn great attention as it is the major alternate source of domestic and drinking water supply. Groundwater samples from selected bore wells were analysed for important physico-chemical attributes by adopting APHA standard methods. From the data obtained, the water quality index (WQI) was calculated by adopting the method developed by Tiwari and Mishra. The WQI values ranged from 49.2 to 409.94. The SF 36 questionnaire of WHO was used in the health survey of residents in the villages bordering the industrial area, to correlate the quality of life with water quality index measured using nine water quality parameters. The Pearson correlation was performed to find the relationship between WQI and quality of life. It was observed that the correlation coefficient ‘r’ was -0.499(p<0.001). On careful examination of the data it was found that most of the water quality parameters were beyond the desired limit prescribed by BIS, making the water unsafe for human consumption.

Hydrochemical profile for assessing the groundwater quality of Sambhar lake City and its Adjoining area

Quality assessment of water is essential to ensure sustainable safe use of it for drinking, agricultural, and industrial purposes. For the same purpose the study was conducted for the samples of water of Sambhar lake city and its adjoining areas. The standard methods of APHA were used to analysis 15 samples collected from hand pumps and tube wells of the specified area. The analytical results show higher concentration of total dissolved solids, electrical conductivity sodium, nitrate, sulfate, and fluoride, which indicate signs of deterioration but values of pH, calcium, magnesium, total hardness, and carbonate are within permissible limits as per WHO standards. From the Hill-piper trilinear diagram, it is observed that the majority of groundwater from sampling stations are sodium-potassium-chloride-sulfate type water. The values of sodium absorption ratio and electrical conductivity of the groundwater were plotted in the US salinity laboratory diagram for irrigation water. Only the one sample fall in C(3)S(1) quality with high salinity hazard and low sodium hazard. Other samples fall in high salinity hazard and high sodium hazard. Chemical analysis of groundwater shows that mean concentration of cation is in order sodium > magnesium > calcium > potassium while for the anion it is chloride > bicarbonate > nitrate > sulfate.

Analytical Studies on Water Quality Index of River Landzu

Problem statement: River Landzu is of particular importance in the study of surface water pollution because effluents from cottage industries, municipal sewage, agricultural and urban run-off are discharged into it bringing about considerable change in the water quality. Approach: This study aimed at using the application of Water Quality Index (WQI) in evaluating the quality of River Landzu for public usage. This was done by subjecting the 120 water samples collected to comprehensive physicochemical analysis using APHA standard methods of analysis. Results: The WQI for the samples was 171.85. The high value of WQI had been found mainly from the higher values of iron, chromium and manganese, COD and turbidity. The results of the analysis when compared with World Health Organization (WHO) and Nigerian Industrial Standard (NIS) permissible limit indicated that the river was polluted and so the water is not safe for domestic use and would need further treatment. Conclusion: The present study demonstrated application of water quality index in estimating/understanding the quality of river water and appeared to be promising in the field of water quality management.

Quality of packaged waters sold in ibadan, nigeria

The inadequacy of pipe borne water supplies in urban centres is a growing problem. As a result, communities resort to buying water from vendors. In recent years, sachet or bottled water became major sources of drinking water in the households and at work. This study aimed at assessing the chemical and bacteriological quality of packaged water sold in Ibadan, the capital of Oyo State with a population over 3.2 million. A total number of 118 samples of water from several commercial brands sold in the city of Ibadan were selected by simple random sampling. These were of threecategories, those that are packed and sealed in bottles by larger factories (bottled water), those sealed in nylon sachets by small scale industries (A Type), and those put in nylon sachets and manually tied by itinerary vendors (B Type). These samples were subjected to physical, chemical and bacteriological analysis. Hanna C 100 spectrophotometer and analytical quality chemical reagents were used for chemical analyses. MacConkey broth (MB) and Brilliant Green Bile Broth (BGBB) were used for bacteriological analysis using multiple tube method as described in APHAStandard Methods. The results showed that while the physical parameters were within WHO limits for drinking water quality guidelines values, 30 % of the samples showed rather poor quality. The pH values ranged between 6.6 - 9.7 and aluminum ranged from 0.00 - 0.34 mg/1, fluoride from 0.01 - 1.87mg/l and cyanide from 0.0 - 0.175 which were not within permissible limits. Bacteriological analysis showed that 5% of the 78 samples (A Type), and 28% of the 30 samples (B Type) tested showed positive coliform counts . The dominant bacteria were Klebsiella sp., Streptococcus faecalisand Pseudomonas aeruginosa. Thus the bottled waters were satisfactory, but the sachet waters were found not satisfactory. Based n the results, it is recommended that the enforcement agencies in the country (NAFDAC and the Ministry of Health) need to get the producers of 'packaged water' to comply with the national drinking water guidelines. Communities on their part should be educated and enlightened on the ill effects of patronizing fake vendors. (Afr. J. Biomed. Res. 11: 251 - 258)Key Words; water quality, Coliform counts, faecal coliforms, pure-water, water vending, urban water, bottled water.

Bio-Treatment of Brewery Effluent Using Enzymes

The feasibility of treating brewery effluent using bio-catalysts (enzymes) was investigated. Carbohydrase, lipase, protease and a mixture enzyme made of carbohydrate and lipase were used. Brewery wastewater samples were collected and analyzed for 96 hrs, at intervals of 12 hrs. The physiochemical properties: biological oxygen demand BOD, chemical oxygen demand COD, total suspended solid (TSS), total dissolved solid TDS, pH, phosphorus (PO4), ammonium nitrogen (NH4-N), total hydrocarbon (THC) were determined using APHA standard method of analysis. The concentrations of the physiochemical properties of the brewery effluent decreased with increasing biodegradation time, for the various enzymes used. However, the different enzymes gave different percentage reductions of each of the physiochemical properties. The order of percentage reduction for the enzyme systems is mixed enzyme &gt; carbohydrase &gt; lipase &gt; protease &gt; control. Hence, the mixed enzyme gave the best results of 90%, 90%, 50%, 100%, 91.6% and 100% reductions for COD, BOD, TSS, NH4-N, PO4 and THC, respectively after 96 hrs. of biotreatment. However, the control gave the least percentage reductions of 6.9%, 5.3%, 16.4%, 7.1%, 5.8% and 50.0% for COD, BOD5, TSS, PO4, NH4-N, and THC respectively.

Rate of phosphoantimonylmolybdenum blue complex formation in acidic persulfate digested sample matrix for total dissolved phosphorus determination: Importance of post-digestion pH adjustment

Acidic persulfate oxidation is one of the most common procedures used to digest dissolved organic phosphorus compounds in water samples for total dissolved phosphorus determination. It has been reported that the rates of phosphoantimonylmolybdenum blue complex formation were significantly reduced in the digested sample matrix. This study revealed that the intermediate products of persulfate oxidation, not the slight change in pH, cause the slowdown of color formation. This effect can be remedied by adjusting digested samples pH to a near neural to decompose the intermediate products. No disturbing effects of chlorine on the phosphoantimonylmolybdenum blue formation in seawater were observed. It is noted that the modification of mixed reagent recipe cannot provide near neutral pH for the decomposition of the intermediate products of persulfate oxidation. This study provides experimental evidence not only to support the recommendation made in APHA standard methods that the pH of the digested sample must be adjusted to within a narrow range of sample, but also to improve the understanding of role of residue from persulfate decomposition on the subsequent phosphoantimonylmolybdenum blue formation.

Environmental risk assessment of River ljana, Ekpan, Delta State Nigeria

The level and distribution of physiochemical contaminants (cadmium, chromium, copper, iron, nickel, lead, zinc, temperature, pH, suspended solids (SS), dissolved solids (DS), conductivity, oil and grease, dissolved oxygen (DO), biochemical oxygen demand (BOD), chemical oxygen demand (COD) and phenol) were investigated in water samples obtained from River Ijana and the Warri Refinery and Petrochemical Company (WRPC) effluents, using APHA standard methods of wastewater analysis. This research is aimed at quantifying the contribution of the refinery effluent, rural/urban runoff, refinery sludge lagoon to the pollution load of the river, and the magnitude of trace metal flux to Tobi creek. The concentration of pollution indicators varies between 0.01 and 0.13 mg L−1 for Cd, 0.01 and 0.09 mg L−1 for Cr, 0.01 and 0.07 mg L−1 for Cu, 0.04 and 0.25 mg L−1 for Fe, 0.02 and 0.09 mg L−1 for Ni, 0.02 and 0.07 mg L−1 for Pb, 0.08 and 0.13mg L−1 for Zn, 28.93 and 31.93°C for temperature, 6.72 and 8.64 for pH, 42.61 and 48.75 mg L−1 for DS, 21.31 and 25.18mg L−1 for SS, 3.22 and 15.11 mg L−1 for oil and grease, 81.01 and 97.02 μ S cm−1 for conductivity, 5.27 and 6.70 mg L−1 for DO, 13.20 and 22.34 mgL−1 for BOD, 40.88 and 52.64mg L−1 for COD and 0.97 and 1.37 mg L−1 for phenol. Correlation analysis shows that P<0.05, and is significant for conductivity, SS, DS, oil and grease, BOD, COD, Cd, Cu, Fe, Ni, Pb and Zn. When compared with WHO/FEPA permissible limits for aquatic ecosystems, our results are indicative of the contribution of pollutant from the refinery effluent. The refinery sludge lagoon is also suspected to be responsible for the elevated concentrations downstream of the river.

Data quality in water analysis: validation of ion chromatographic method for the determination of routine ions in potable water

Ion chromatography provides a simple, fast, small sample volume demanding, and fit-for-purpose methodology for the concurrent determination of 10 ions (F −, Cl −, Br −, NO 3 −, PO 4 3−, SO 4 2−, Na +, K +, Ca 2+ and Mg 2+) in surface, ground and potable water samples. Current law legislations, as well as the need to constantly provide accurate and reliable results, enforce public sector laboratories to practice quality management system, according to the EN ISO 17025 standard. In this paper, the work that was undertaken for the accreditation of the above determinations at the chemical laboratory of EYDAP SA, is presented. The laboratory has developed two in-house methods, which are carried out simultaneously by a dual chromatographic system. The method for the analysis of anions is based on the 4110B APHA standard method and the one for the cations based on the ISO14911. Deviations from the standard procedure made a full method validation imperative, therefore, for all 10 ions, method characteristics were determined and assessed towards the fitness-for-purpose scope (range of measurement, calibration, method detection level, level of quantification, repeatability, reproducibility, precision, accuracy, peak resolution). Additionally, measurement uncertainty was determined and procedures for daily measurement quality control, assessment of individual analyst capability, measurement, sample and reagent traceability, and regular participation in proficiency testing schemes were implemented. Methodology and results for method validation, uncertainty quantification and quality control is presented in detail in the full paper.

SEQUENTIAL INJECTION ANALYSIS (SIA) FOR IBN ZAHR WATER QUALITY CONTROL

This manuscript describes the adaptation of Sequential Injection Analysis (SIA) for the determination of silica, iron, ammonia, and phosphates, in water as a routine method being used by the quality control unit of a Petrochemical industry in Saudi Arabia (Ibn Zahr). The results obtained from the adopted SIA methods were found to be in agreement with results obtained from batch spectrophotometric APHA Standard methods (American Public Health Association).SIA has the additional advantage of reducing cost by minimizin g time, amount of reagent consumed, man power required and improved accuracy of analysis due to computer aided analysis procedure.

A multisyringe flow injection method for the automated determination of sulfide in waters using a miniaturised optical fiber spectrophotometer

In this paper, a fully software-controlled multisyringe flow injection (MSFIA) spectrophotometric system is proposed for the determination of sulfide in environmental and waste waters. The implementation of ancillary solenoid valves into the flow network allows a multitude of injection modalities to be explored, the selected modality being directly dependent on the aim of the assays. The multicommuted sandwich-type approach is introduced in this work as an efficient means to warrant high sensitivity for the particular assay with excellent repeatabilities and a considerable reagent saving. Moreover, a high injection frequency may be easily attained by carrying out a multiple injection modality during a single forward displacement of the piston driver bar. The interfacing of the robust and versatile multisyringe piston pump with an optical fiber plug-in spectrophotometer furnished with a light emitting diode enables the miniaturization of the flow analyzer, which is thus readily adaptable to in-situ and real-time monitoring schemes. The flow method is based on the coupling Fischer’s reaction of sulfide with N, N-dimethyl- p-phenylenediamine in the presence of Fe(III) as oxidizing reagent in a 0.7 M HCl medium. Careful selection of the physical and chemical variables enabled coefficients of variations better than 1.5% ( n = 10) at the 1 mg l −1 level for both injection modalities. Dynamic working ranges of 0.2–2.0 and 0.5–5 mg l −1 sulfide for sandwich and multiple injection techniques, and detection limits of 0.09 and 0.15 mg l −1, respectively, were obtained. Furthermore, the sandwich modality featured an average slope of 0.43 ± 0.02 l mg −1 calculated from 10 day-to-day calibration plots. This result reveals better sensitivity than other flowing stream methods described in the literature. The multiple injection technique allowed an improvement of the injection throughput up to 80 h −1, although a decrease of sensitivity was concomitantly observed (average slope of 0.17 ± 0.01 l mg −1). The multisyringe flow method was successfully applied to the determination of sulfide in different spiked water matrices (namely, mineral, tap, freshwater, seawater and wastewater) with recoveries ranging from 96 to 104%. Good agreement was also found in water samples between the MSFIA results and those of the batch APHA-standard method.

ENUMERATING 3MTM PETRIFILMTM AEROBIC COUNT PLATES USING THE PETRISCAN® AUTOMATED COLONY COUNTER

ABSTRACTIn the food and dairy industries, aerobic plate counts are determined by a time‐consuming and laborious hand‐counting method. The PetriScan ® automated colony counter was developed to improve efficiency in the microbiology laboratory. In this study, colony counts of food, dairy, and milk products plated on 3MTM PetrifilmTM Aerobic Count Plates were compared using both automated and manual count plate methods. For sample variation, 16 different food, dairy, and milk products were used. Samples were prepared and serially diluted using Butterfield's diluent according to approved AOAC methods and APHA's Standard Methods. Plates were inoculated, incubated, and counted according to AOAC methods. For data collection, plates with counts between 5 and 300 colonies were included. A total of 55 low (5–30), 29 medium (31–100), and 23 high (101–300) count plates were used. Duplicate results were recorded for both methods; hand counts were tallied by two scientists. The duplicates of the mean log values for manual counts varied by 0.0005 and 0.0007, and the duplicates for the automated counts varied by 0.0011. The mean log value difference between the automated and manual counts for pooled data was 0.035. The correlation coefficient for the regression line comparing the automated and manual count methods for pooled data was 0.98. The regression equation was y = 0.9257x + 0.0781. These results demonstrate that the PetriScan® automated colony counter is a comparable and practical alternative to the standard method of manually counting plates.

The APHA standard method for the enumeration of somatic coliphages in water has low efficiency of plating

The standard method for the enumeration of somatic coliphages in water proposed by the American Public Health Association recommends the use of single layer plaque assays with 5 ml sample and the direct use of frozen and thawed host E. coli cultures. In assays of spiked river water the efficiency of plating (e.o.p.) of the standard method, using frozen/thawed host cultures, was significantly lower than comparable assays using unfrozen host cultures. Frozen/thawed cultures also produced significantly lower efficiency of plating in scaled up versions of the standard method using both 50 and 100 ml sample. The e.o.p. varied from 39.0–46.1% with frozen/thawed cultures and 67.7–74.4% with unfrozen cultures at OD 0.5, relative to overnight cultures. It is therefore recommended that overnight cultures are used in place of frozen/thawed cultures in the APHA standard method and scaled up versions of it.