Impacts of the reduction of nutrient levels on bacterial water quality in distribution systems.

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 microg/liter in the plant effluent and 91 microg/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 x 10(5) to 1.4 x 10(4) CFU/cm(2)) and 0.5-log unit (from 2.7 x 10(5) to 7.8 x 10(4) CFU/cm(2)) 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.).     

Muramic Acid Measurements for Bacterial Investigations in Marine Environments by High-Pressure Liquid Chromatography

Muramic acid, a constituent of procaryotic cell walls, was assayed by high-pressure liquid chromatography in samples from several marine environments (water column, surface microlayer, and sediment) and a bacterial culture. It is used as a microbial biomass indicator. The method gave a good separation of muramic acid from interfering compounds with satisfactory reproducibility. A pseudomonad culture had a muramic acid content of 4.7 × 10⁻¹⁰ to 5.3 × 10⁻¹⁰ μg per cell during growth. In natural water samples, highly significant relationships were found between muramic acid concentrations and bacterial numbers for populations of 10⁸ to 10¹¹ cells per liter. The muramic acid content in natural marine water decreased from 5.3 × 10⁻¹⁰ to 1.6 × 10⁻¹⁰ μg per cell with increasing depth. In coastal sediments exposed to sewage pollution, concentrations of muramic acid, ATP, organic carbon, and total amino acids displayed a parallel decrease with increasing distance from the sewage outlet. Advantages of muramic acid measurement by high-pressure liquid chromatography are its high sensitivity and reduction of preparation steps, allowing a short time analysis.     

Optimization of a Reusable Hollow-Fiber Ultrafilter for Simultaneous Concentration of Enteric Bacteria, Protozoa, and Viruses from Water

The detection and identification of pathogens from water samples remain challenging due to variations in recovery rates and the cost of procedures. Ultrafiltration offers the possibility to concentrate viral, bacterial, and protozoan organisms in a single process by using size-exclusion-based filtration. In this study, two hollow-fiber ultrafilters with 50,000-molecular-weight cutoffs were evaluated to concentrate microorganisms from 2- and 10-liter water samples. When known quantities (10⁵ to 10⁶ CFU/liter) of two species of enteric bacteria were introduced and concentrated from 2 liters of sterile water, the addition of 0.1% Tween 80 increased Escherichia coli strain K-12 recoveries from 70 to 84% and Salmonella enterica serovar Enteritidis recoveries from 36 to 72%. An E. coli antibiotic-resistant strain, XL1-Blue, was recovered at a level (87%) similar to that for strain K-12 (96%) from 10 liters of sterile water. When E. coli XL1-Blue was introduced into 10 liters of nonsterile Rio Grande water with higher turbidity levels (23 to 29 nephelometric turbidity units) at two inoculum levels (9 × 10⁵ and 2.4 × 10³ per liter), the recovery efficiencies were 89 and 92%, respectively. The simultaneous addition of E. coli XL1-Blue (9 × 10⁵ CFU/liter), Cryptosporidium parvum oocysts (10 oocysts/liter), phage T1 (10⁵ PFU/liter), and phage PP7 (10⁵ PFU/liter) to 10 liters of Rio Grande surface water resulted in mean recoveries of 96, 54, 59, and 46%, respectively. Using a variety of surface waters from around the United States, we obtained recovery efficiencies for bacteria and viruses that were similar to those observed with the Rio Grande samples, but recovery of Cryptosporidium oocysts was decreased, averaging 32% (the site of collection of these samples had previously been identified as problematic for oocyst recovery). Results indicate that the use of ultrafiltration for simultaneous recovery of bacterial, viral, and protozoan pathogens from variable surface waters is ready for field deployment.     

Bacterioplankton and Organic Carbon Dynamics in the Lower Mesohaline Chesapeake Bay

The mesohaline portion of the Chesapeake Bay is subject to annual summertime hypoxia and anoxia in waters beneath the pycnocline. This dissolved oxygen deficit is directly related to salinity-based stratification of the water column in combination with high levels of autochthonously produced organic matter and a very high abundance of metabolically active bacteria. Throughout the water column in the lower, mesohaline part of the bay, between the Potomac and Rappahannock rivers, near the southern limit of the mainstem anoxia, bacterial abundance often exceeded 10 × 10⁶ cells per ml and bacterial production exceeded 7 × 10⁹ cells per liter per day during summer. Bacterial biomass averaged 34% (range, 16 to 126%) of the phytoplankton biomass in summer. These values are equal to or greater than those found farther north in the bay, where the oxygen deficit is more severe. Seasonal variations in bacterial abundance and production were correlated with phytoplankton biomass (lag time, 7 to 14 days), particulate organic carbon and nitrogen, and particulate biochemical oxygen demand in spring; but during summer, they were significantly correlated only with dissolved biochemical oxygen demand. During summer, dissolved biochemical oxygen demand can account for 50 to 60% of the total biochemical oxygen demand throughout the water column and 80% in the bottom waters. There is a clear spring-summer seasonal shift in the production of organic matter and in the coupling of bacteria and autochthonous organic matter. The measurement of dissolved, microbially labile organic matter concentrations is crucial in understanding the trophic dynamics of the lower mesohaline part of the bay. The absolute levels of organic matter in the water column and the bacterial-organic carbon relationships suggest that a lower bay source of organic matter fuels the upper mesohaline bay oxygen deficits.     

Identification of Nonpoint Sources of Fecal Pollution in Coastal Waters by Using Host-Specific 16S Ribosomal DNA Genetic Markers from Fecal Anaerobes

We describe a new PCR-based method for distinguishing human and cow fecal contamination in coastal waters without culturing indicator organisms, and we show that the method can be used to track bacterial marker sequences in complex environments. We identified two human-specific genetic markers and five cow-specific genetic markers in fecal samples by amplifying 16S ribosomal DNA (rDNA) fragments from members of the genus Bifidobacterium and the Bacteroides-Prevotella group and performing length heterogeneity PCR and terminal restriction fragment length polymorphism analyses. Host-specific patterns suggested that there are species composition differences in the Bifidobacterium and Bacteroides-Prevotella populations of human and cow feces. The patterns were highly reproducible among different hosts belonging to the same species. Additionally, all host-specific genetic markers were detected in water samples collected from areas frequently contaminated with fecal pollution. Ease of detection and longer survival in water made Bacteroides-Prevotella indicators better than Bifidobacterium indicators. Fecal 16S rDNA sequences corresponding to our Bacteroides-Prevotella markers comprised closely related gene clusters, none of which exactly matched previously published Bacteroides or Prevotella sequences. Our method detected host-specific markers in water at pollutant concentrations of 2.8 × 10⁻⁵ to 2.8 × 10⁻⁷ g (dry weight) of feces/liter and 6.8 × 10⁻⁷ g (dry weight) of sewage/liter. Although our aim was to identify nonpoint sources of fecal contamination, the method described here should be widely applicable for monitoring spatial and temporal fluctuations in specific bacterial groups in natural environments.     

Escherichia coli Behavior in the Presence of Organic Matter Released by Algae Exposed to Water Treatment Chemicals

When exposed to oxidation, algae release dissolved organic matter with significant carbohydrate (52%) and biodegradable (55 to 74%) fractions. This study examined whether algal organic matter (AOM) added in drinking water can compromise water biological stability by supporting bacterial survival. Escherichia coli (1.3 × 10⁵ cells ml⁻¹) was inoculated in sterile dechlorinated tap water supplemented with various qualities of organic substrate, such as the organic matter coming from chlorinated algae, ozonated algae, and acetate (model molecule) to add 0.2 ± 0.1 mg of biodegradable dissolved organic carbon (BDOC) liter⁻¹. Despite equivalent levels of BDOC, E. coli behavior depended on the source of the added organic matter. The addition of AOM from chlorinated algae led to an E. coli growth equivalent to that in nonsupplemented tap water; the addition of AOM from ozonated algae allowed a 4- to 12-fold increase in E. coli proliferation compared to nonsupplemented tap water. Under our experimental conditions, 0.1 mg of algal BDOC was sufficient to support E. coli growth, whereas the 0.7 mg of BDOC liter⁻¹ initially present in drinking water and an additional 0.2 mg of BDOC acetate liter⁻¹ were not sufficient. Better maintenance of E. coli cultivability was also observed when AOM was added; cultivability was even increased after addition of AOM from ozonated algae. AOM, likely to be present in treatment plants during algal blooms, and thus potentially in the treated water may compromise water biological stability.     

Evidence for a Terpene-Based Food Chain in the Gulf of Alaska

A mixture of ¹⁴C-terpenes was prepared from conifer seedlings and introduced into fresh seawater samples taken near Seward, Alaska. Initial rates of oxidation by the indigenous bacteria were linear and faster than the rates of toluene oxidation. Turnover times were 4 to 19 days. Autoradiographic measurements with ³H-terpenes indicated that at least 10% of the 0.6 × 10⁹ to 2.7 × 10⁹ bacteria per liter present could catabolize terpenes. The rate of terpene oxidation, 24 μg of terpenes per g of cells per h with 3 μg of terpenes added per liter, was a constant function of bacterial biomass. The specific affinity of the process was estimated to be between 8.1 and 81 liters/g of cells per h, indicating a high state of induction and the probable presence of terpenes. Terpene-oxidizing bacteria were grown on [¹⁴C]alanine and added to fresh seawater samples. Transfer of the bacterial radioactivity into larger particles at a rate of 146 pg/liter per h from the 2.3 × 10⁹ organisms added indicated that any terpenes present would participate in the food chain.     

Characterization of Persistent Virus-Like Particles in Two Acetate-Fed Methanogenic Reactors

The objective of this study was to characterize the morphology, size-distribution, concentration and genome size of virus-like particles (VLPs) in two acetate-fed Methanosaeta-dominated reactors to better understand the possible correlation between viruses and archaeal hosts. The study reactors were dominated by a single genus of acetoclastic methanogen, Methanosaeta, which was present at 6 to 13 times higher than the combined bacterial populations consisting of Proteobacteria, Firmicutes, and Bacteroidetes. Epifluorescent microscopy showed VLPs concentration of 7.1 ± 1.5×10⁷ VLPs/ml and 8.4 ± 4.3×10⁷ VLPs/ml in the two laboratory reactors. Observations of no detectable import of VLPs with the reactor feed combined long operational time since the last inocula were introduced suggests that the VLP populations were actively propagating in the reactors. Transmission electron microscopy images showed VLPs with morphology consistent with Siphoviridae in both reactors, and VLPs with morphologies consistent with Myoviridae in one of the reactors. The morphology, size-distribution and genome size of VLPs were distinct between reactors suggesting that unique viral populations inhabited each reactor, though the hosts of these VLPs remain unclear.     

Biological Instability in a Chlorinated Drinking Water Distribution Network

The purpose of a drinking water distribution system is to deliver drinking water to the consumer, preferably with the same quality as when it left the treatment plant. In this context, the maintenance of good microbiological quality is often referred to as biological stability, and the addition of sufficient chlorine residuals is regarded as one way to achieve this. The full-scale drinking water distribution system of Riga (Latvia) was investigated with respect to biological stability in chlorinated drinking water. Flow cytometric (FCM) intact cell concentrations, intracellular adenosine tri-phosphate (ATP), heterotrophic plate counts and residual chlorine measurements were performed to evaluate the drinking water quality and stability at 49 sampling points throughout the distribution network. Cell viability methods were compared and the importance of extracellular ATP measurements was examined as well. FCM intact cell concentrations varied from 5×10³ cells mL⁻¹ to 4.66×10⁵ cells mL⁻¹ in the network. While this parameter did not exceed 2.1×10⁴ cells mL⁻¹ in the effluent from any water treatment plant, 50% of all the network samples contained more than 1.06×10⁵ cells mL⁻¹. This indisputably demonstrates biological instability in this particular drinking water distribution system, which was ascribed to a loss of disinfectant residuals and concomitant bacterial growth. The study highlights the potential of using cultivation-independent methods for the assessment of chlorinated water samples. In addition, it underlines the complexity of full-scale drinking water distribution systems, and the resulting challenges to establish the causes of biological instability.     

Occurrence of Human Adenoviruses at Two Recreational Beaches of the Great Lakes

Human adenoviruses (HAdVs) have been related to several waterborne diseases such as acute gastroenteritis, conjunctivitis, and respiratory illness, and it has been shown that an important human exposure pathway is through recreational waters. However, HAdV occurrence at recreational freshwater beaches has not been previously investigated. In this study, a total of 58 water samples were collected from two recreational beaches on Lake Michigan (i.e., Silver Beach and Washington Park Beach) during the summer of 2004. Occurrences of HAdVs in these lake samples were determined using two hexon-based real-time PCR assays (one for monitoring all 51 serotypes of HAdVs and another for specifically detecting F species HAdVs, i.e., serotypes 40 and 41) and compared to an integrated cell culture (ICC) PCR method. The real-time PCR results showed that 8 of 30 Silver Beach samples and 6 of 28 Washington Park Beach samples contained HAdVs, and F species HAdVs were detected in three of these positive samples. The concentrations of HAdVs ranged from (1.7 ± 0.7) × 10¹ to (3.4 ± 0.8) × 10² and from (7 ± 2) × 10⁰ to (3.8 ± 0.3) × 10³ virus particles/liter for Silver Beach and Washington Park Beach, respectively. F species HAdVs were detected at levels ranging from (4.8 ± 0.8) × 10¹ to (4.6 ± 1.5) × 10² virus particles/liter. Approximately 60% of the ICC-PCR analyses agreed with the real-time PCR results. This study revealed the occurrence of HAdVs at Lake Michigan recreational beaches. Given the potential health risks, further assessment regarding sources, virus transport, and survival is needed to improve the safety of the region.     

Identification of Bacteria in Biofilm and Bulk Water Samples from a Nonchlorinated Model Drinking Water Distribution System: Detection of a Large Nitrite-Oxidizing Population Associated with Nitrospira spp.

In a model drinking water distribution system characterized by a low assimilable organic carbon content (<10 μg/liter) and no disinfection, the bacterial community was identified by a phylogenetic analysis of rRNA genes amplified from directly extracted DNA and colonies formed on R2A plates. Biofilms of defined periods of age (14 days to 3 years) and bulk water samples were investigated. Culturable bacteria were associated with Proteobacteria and Bacteriodetes, whereas independently of cultivation, bacteria from 12 phyla were detected in this system. These included Acidobacteria, Nitrospirae, Planctomycetes, and Verrucomicrobia, some of which have never been identified in drinking water previously. A cluster analysis of the population profiles from the individual samples divided biofilms and bulk water samples into separate clusters (P = 0.027). Bacteria associated with Nitrospira moscoviensis were found in all samples and encompassed 39% of the sequenced clones in the bulk water and 25% of the biofilm community. The close association with Nitrospira suggested that a large part of the population had an autotrophic metabolism using nitrite as an electron donor. To test this hypothesis, nitrite was added to biofilm and bulk water samples, and the utilization was monitored during 15 days. A first-order decrease in nitrite concentration was observed for all samples with a rate corresponding to 0.5 × 10⁵ to 2 × 10⁵ nitrifying cells/ml in the bulk water and 3 × 10⁵ cells/cm² on the pipe surface. The finding of an abundant nitrite-oxidizing microbial population suggests that nitrite is an important substrate in this system, potentially as a result of the low assimilable organic carbon concentration. This finding implies that microbial communities in water distribution systems may control against elevated nitrite concentrations but also contain large indigenous populations that are capable of assisting the depletion of disinfection agents like chloramines.     

Experimental Evaluation of Conversion Factors for the [3H]Thymidine Incorporation Assay of Bacterial Secondary Productivity

The relationship between bacterial growth and incorporation of [methyl-³H]thymidine in oligotrophic lake water cultures was investigated. Prescreening, dilution, and addition of organic and inorganic nutrients were treatments used to prevent bacterivory and stimulate bacterial growth. Growth in unmanipulated samples was estimated through separate measurements of grazing losses. Both bacterial number and biovolume growth responses were measured, and incorporation of [³H]thymidine in both total macromolecules and nucleic acids was assayed. The treatments had significant effects on conversion factors used to relate thymidine incorporation to bacterial growth. Cell number-based factors ranged from 1.1 × 10¹⁸ to 38 × 10¹⁸ cells mol of total thymidine incorporation⁻¹ and varied with treatment up to 10-fold for the same initial bacterial assemblage. In contrast, cell biovolume-based conversion factors were similar for two treatment groups across a 16-fold range of [³H]thymidine incorporation rates: 5.54 × 10¹⁷ μm³ mol of total thymidine incorporation⁻¹ and 15.2 × 10¹⁷ μm³ mol of nucleic acid incorporation⁻¹. Much of the variation in cell number-based conversion factors was related to changes in apparent mean cell volume of produced bacteria. Phosphorus addition stimulated [³H]thymidine incorporation more than it increased bacterial growth, which resulted in low conversion factors.     

Broad Distribution of Diverse Anaerobic Ammonium-Oxidizing Bacteria in Chinese Agricultural Soils

Anaerobic ammonium-oxidizing (anammox) bacteria have been detected in many marine and freshwater ecosystems. However, little is known about the distribution, diversity, and abundance of anammox bacteria in terrestrial ecosystems. In this study, anammox bacteria were found to be present in various agricultural soils collected from 32 different locations in China. Phylogenetic analysis of the 16S rRNA genes showed “Candidatus Brocadia,” “Candidatus Kuenenia,” “Candidatus Anammoxoglobus,” and “Candidatus Jettenia” in the collected soils, with “Candidatus Brocadia” being the dominant genus. Quantitative PCR showed that the abundance of anammox bacteria ranged from 6.38 × 10⁴ ± 0.42 × 10⁴ to 3.69 × 10⁶ ± 0.25 × 10⁶ copies per gram of dry weight. Different levels of diversity, composition, and abundance of the anammox bacterial communities were observed, and redundancy analysis indicated that the soil organic content and the distribution of anammox communities were correlated in the soils examined. Furthermore, Pearson correlation analysis showed that the diversity of the anammox bacteria was positively correlated with the soil ammonium content and the organic content, while the anammox bacterial abundance was positively correlated with the soil ammonium content. These results demonstrate the broad distribution of diverse anammox bacteria and its correlation with the soil environmental conditions within an extensive range of Chinese agricultural soils.     

Effects of 2-Bromoethanesulfonic Acid and 2- Chloroethanesulfonic Acid on Acetate Utilization in a Continuous-Flow Methanogenic Fixed-Film Column

2-Bromoethanesulfonic acid (BESA) and 2-chloroethanesulfonic acid (CESA) have been reported to be potent inhibitors of methane formation during methanogenic decomposition in batch cultures. However, in a laboratory-scale continuous-flow methanogenic fixed-film column containing a predominance of acetate-decarboxylating methanogens, BESA at 6 × 10⁻⁴ M produced only a 41% inhibition of acetate utilization, and CESA at 5.4 × 10⁻⁴ M produced a 37% inhibition of acetate utilization. BESA and CESA concentrations were not monitored in the effluent, so their fate is unknown. The organisms in the column were capable of degrading trace halogenated aliphatic compounds (~30 μg/liter) with acetate (100 mg/liter) as the primary substrate. Previous exposure of the cells to halogenated organic compounds may have conferred resistance to BESA and CESA. Degradation of the inhibitor compounds is another possible explanation for the observed effects.     

Substrate Utilization by an Oxalate-Consuming Spirillum Species in Relation to Its Growth in Ozonated Water

The nutritional versatility of a vibrio-shaped, oxalate-utilizing isolate, strain NOX, obtained from tap water supplied with low concentrations of formate, glyoxylate, and oxalate, was determined by growth experiments with low-molecular-weight carbon compounds at high (grams per liter) and very low (micrograms per liter) concentrations. The organism, which was identified as a Spirillum species, appeared to be specialized in the utilization of a number of carboxylic acids. Yields of 2.9 × 10⁶ CFU/μg of oxalate C and 1.2 × 10⁷ CFU/μg of acetate C were obtained from growth experiments in tap water supplied with various low amounts of either oxalate or acetate. A substrate saturation constant of 0.64 μM oxalate was calculated for strain NOX from the relationship between growth rate and concentration of added oxalate. Maximum colony counts of strain NOX grown in ozonated water (dosages of 2.0 to 3.2 mg of O₃ per liter) were 15 to 20 times larger than the maximum colony counts of strain NOX grown in water before ozonation. Based on the nutritional requirements of strain NOX, it was concluded that carboxylic acids were produced by ozonation. Oxalate concentrations were calculated from the maximum colony counts of strain NOX grown in samples of ozonated water in which a non-oxalate-utilizing strain of Pseudomonas fluorescens had already reached maximum growth. The oxalate concentrations obtained by this procedure ranged from 130 to 220 μg of C/liter.     

Comparison of Point-of-Use Technologies for Emergency Disinfection of Sewage-Contaminated Drinking Water

Four point-of-use disinfection technologies for treating sewage-contaminated well water were compared. Three systems, based on flocculant-disinfectant packets and N-halamine chlorine and bromine contact disinfectants, provided a range of 4.0 to >6.6 log₁₀ reductions (LR) of naturally occurring fecal indicator and heterotrophic bacteria and a range of 0.9 to >1.9 LR of coliphage.Disasters and flooding can overwhelm sanitation infrastructure, leading to sewage contamination of potable waters. This may be routine during the wet season in many parts of the world and spreads numerous waterborne diseases (21). Point-of-use (POU) water treatment has reduced the incidence of diarrheal disease when used for household drinking water (3, 4, 6, 13) and is now being promoted for disaster relief. While POU systems have recently been reviewed (14), to our knowledge there has been no direct, experimental comparison for treating actual sewage-contaminated waters. In this study, the efficacies of four POU disinfection systems (based on sodium dichloroisocyanurate [NaDCC] tablets, a flocculent-disinfectant powder, and chlorine and bromine contact disinfectant cartridges) in reducing the concentrations of six microbial indicators in well water contaminated with raw sewage were compared.The NaDCC tablets (67 mg; Aquatabs; Medentech, Wexford, Ireland), used for disinfection in low-turbidity water, have shown preliminary efficacy for routine household drinking water treatment (3, 4). The flocculant-disinfectant packet (4 g; PUR; Procter & Gamble Co., Cincinnati, OH) includes Fe₂(SO₄)₃, bentonite, Na₂CO₃, chitosan, polyacrylamide, KMnO₄, and Ca(OCl)₂ (13). It achieved >7.3 log₁₀ reductions (LR) of 24 bacteria species; >4.6 LR of poliovirus and rotavirus in EPA no. 2 test water (turbidity, >30 nephelometric turbidity units [NTU]) (15); and reduced diarrheal illness in Guatemala, Liberia, Kenya, and Pakistan (6, 7, 11, 13).HaloPure canisters (Eureka Forbes, Mumbai, India) contain N-halamine polymer disinfectant beads, poly[1,2-dichloro-5-methyl-5-(4′-vinylphenyl)hydrantoin] for chlorine canisters, and poly[1,2-dibromo-5-methyl-5-(4′-vinylphenyl)hydrantoin] for bromine canisters. Seeded laboratory trials achieved >6.8 LR for Escherichia coli and Staphylococcus aureus as water was passed through the canisters (2). The Cl-contact (producing residuals ranging from 0 to 0.6 mg/liter) and Br-contact (with residuals of 0.68 to 1.8 mg/liter) disinfectants achieved 2.9 LR and 5.0 LR of the bacteriophage MS2, respectively, and 27.5% and 88.5% reductions of the algal toxin microcystin, respectively (5).Sewage-contaminated water was prepared by mixing 9 liters of potable, nonchlorinated well water (pH 7.8; turbidity, 0.33 NTU; Williamston, MI) with 1 liter of raw sewage (City of East Lansing Wastewater Treatment Plant, MI) with an average pH of 6.6 ± 0.1, a biochemical oxygen demand of 144 ± 36 mg/liter, a concentration of total suspended solids of 146 ± 31 mg/liter, and a turbidity of 132 ± 12 NTU. Three disinfection trials were conducted at room temperature for each POU system on three different days to allow for variance in sewage strength. The turbidities of 1:10 dilutions of raw sewage averaged 7.5 ± 2.0 NTU. Table ​Table11 lists the indicator microorganism concentrations in the influent and effluent for each system.

TABLE 1.

Concentrations of influent and 30-min-effluent microorganisms for POU disinfectant systems treating sewage-contaminated water

Influence of Cyanobacterial Hyperscum on Heterotrophic Activity of Planktonic Bacteria in a Hypertrophic Lake

The response of the planktonic heterotrophic bacterial community to the buildup and breakdown of a semipermanent, crusted, floating cyanobacterial mat, or hyperscum, that covered 1 to 2 ha was studied in a hypertrophic lake (Hartbeespoort Dam, South Africa). The initial response of bacteria in the main basin to the release of dissolved organic carbon (DOC) from the hyperscum 1 km away was an increase in activity per cell from 35 × 10⁻¹² to 153 × 10⁻¹² μg of C cell⁻¹ h⁻¹ for total cell counts, while activity per cell for metabolically active cells increased from 19 × 10⁻¹¹ to 85 × 10⁻¹¹ μg of C cell⁻¹ h⁻¹. No major population growth occurred at this stage. Later, with the continuous supply of DOC from the hyperscum, total bacterial numbers increased from 6.6 × 10⁶ to 20 × 10⁶ cells ml⁻¹, while the activity per cell declined. Metabolically active bacteria followed the same trend. Shorter-term DOC increases caused only increases in bacterial activity per cell. The data from Hartbeespoort Dam demonstrate an interesting and little-documented mechanism by which aquatic bacteria respond to increased DOC concentration and which may be universal for aquatic systems.     

Bacterial and Fungal Numbers in Ruminal and Cecal Contents of the Blue Duiker (Cephalophus monticola)

Total and cellulolytic bacterial and fungal numbers were determined in ruminal and cecal contents of 20 blue duikers (Cephalophus monticola). The animals were equally divided by sex and fed two diets, either high roughage or high concentrate. The mean concentration for total bacterial numbers in the rumen was 26.0 × 10⁸/g of contents, with values ranging from 2 × 10⁸/g to 93 × 10⁸/g. Cellulolytic numbers averaged 6.0 × 10⁸/g with a range of 1.5 × 10⁸/g to 24.0 × 10⁸/g. No differences related to sex or diet were found. In contrast, total bacterial numbers in the cecum differed between diets (P < 0.02), i.e., 1,046 × 10⁶ bacteria per g for animals fed the high-forage diet compared with 166 × 10⁶/g for those fed the high-concentrate diet. Cellulolytic bacterial counts in the cecal contents averaged 3.1 and 7.0% of the total counts for the high-forage and high-concentrate diets, respectively. Low concentrations of fungi were found in both ruminal and cecal contents of some, but not all, animals. Unexpectedly, concentrations of bacteria and fungi in the rumen and cecum were highly correlated with their total numbers (concentration multiplied by total weight of contents).     

Microbial Flora of Pond-Reared Brown Shrimp (Penaeus aztecus)

Agar plate counts and microbial types are reported for brown shrimp reared in 2-acre natural marshland and in 0.5-acre artificial ponds during June to October 1970. Bacterial counts of pond-reared shrimp ranged from 5 × 10⁴ to 5.5 × 10⁶ per g. At final harvest in October, bacterial counts ranged from 2 × 10⁵ to 5.5 × 10⁶ per g. In marsh ponds, bacterial counts of shrimp and pond water were lowest in August when both water temperature and salinity were high. Coryneform bacteria and to a lesser extent Vibrio were the predominant isolates from fresh pond shrimp. Shrimp stored at 3 to 5 C for 7 days were acceptable as judged by appearance and odor. Between 7 and 14 days of refrigerated storage, bacterial counts increased sharply and about 50% of the samples became unacceptable. Refrigerated storage of pond shrimp caused increases in coryneform bacteria and micrococci and decreases in Vibrio, Flavobacterium, Moraxella, and Bacillus species. Pseudomonas species were not significant in fresh or stored pond shrimp. The microbial flora of pond water usually was dominated by coryneform bacteria, Flavobacterium, Moraxella, and Bacillus species.