Fecal Coliform Densities Research Articles

Dinámica espaciotemporal de la calidad de agua en la laguna Las Peonías (Zulia, Venezuela): 2013-2016

La laguna Las Peonías es un refugio para numerosas especies tropicales y una fuente alternativa de agua para la población humana. En este trabajo, se explica la dinámica espaciotemporal de la calidad del agua superficial en la laguna, con base en sus características fisicoquímicas y bacteriológicas. Para ello, se realizaron 16 campañas de recolección de muestras, en 10 sitios de estudio, incluyendo las principales fuentes de agua: cañadas Iragorri y Fénix y caño Araguato (canal de intercambio con el lago de Maracaibo), entre septiembre de 2013 y septiembre de 2016, durante las mareas alta y baja. En general, no se observaron diferencias significativas (p>0,05) para las magnitudes de los 22 parámetros analizados, con respecto al régimen de mareas del lago de Maracaibo. Las concentraciones de materia orgánica (DBO y DQO), nitrógeno total y fósforo total fueron de 0,20-22,88 mg/l; 5,25-2074,07 mg/l; 0,52-17,37 mg/l y 0,75-11,49 mg/l, respectivamente; valores típicos de ecosistemas hipereutróficos. Las densidades de bacterias coliformes totales y fecales se presentaron entre 3,01- 2,40×104 NMP/100 ml; por lo que incumplen los límites permisibles de la normativa venezolana para aguas recreacionales (contacto humano parcial y total). Los aportes de agua a través de la cañada Iragorri y el caño Araguato, determinaron la variabilidad espacial de la calidad de agua, mientras que la dinámica temporal estuvo influenciada por las precipitaciones, fundamentalmente hacia finales del periodo de estudio (agosto y septiembre de 2016). Este trabajo contribuye al entendimiento ecológico del ecosistema, al tiempo que sienta las bases para su recuperación ambiental y el establecimiento de planes de manejo de su recurso hídrico.

Human impact of septic tank effluent on groundwater quality in the rural area of Ain Soltane (Ain Defla), Algieria

Abstract The impact of individual septic tank effluent on groundwater quality was investigated in the rural area of the Ain Soltane municipality in Algeria. This area has an important number of individual septic tanks, and it is devoid of a drinking water supply and sewerage systems. The septic tank is a pre-treatment solution of sewage by bacteria living without oxygen (anaerobic). The alluvial aquifer in this area is covered by a layer of good permeability on the surface, which can pollute groundwater by vertical transport of pollutants through the soil, including microbial contamination. Groundwater samples were collected from 33 wells in the dry period of 2016. The monitoring of groundwater quality has shown a significant degree of organic and inorganic pollution in the majority of wells, with very high concentrations of sulphate and chloride exceeding 450 mg/l and 250 mg/l respectively. The analyzes also show the presence of bacterial germs in the groundwater of which the origin is faecal (faecal coliform densities are above 10 organisms per 100 ml, and the Total Streptococcus is more than 240 colonies per 100 ml). Monitoring confirms the contamination of these wells from septic tanks and that it was moving into groundwater, which makes it unfit for drinking due to the pathogenic germs. This poses a major problem for public health. This study has identified the effects of septic tank effluent on groundwater quality in this area.

Full scale study of Class A biosolids produced by thermal hydrolysis pretreatment and anaerobic digestion

Biosolids are the solid by-product of wastewater treatment and contain high-organic matter and nutrient content, which can be utilized in food production and gardening. In 2014, this study’s target nutrient recovery facility (NRF) in the Mid-Atlantic region of the U.S. adopted thermal hydrolysis pretreatment (THP) and anaerobic digestion (AD) to upgrade biosolids from Class B (lime-stabilized) to Class A. The pathogen, nutrients, and metals contents were compared with that of Class B biosolids from the same facility throughout a one-year period. Following optimization and equilibrium, stable biosolids were produced that satisfied all Environmental Protection Agency (EPA) Class A biosolids standards. Class A biosolids produced had fecal coliform density consistently below the 1000 MPN/g d.w. limit set by the EPA, at 35.85 ± 81.10 MPN/g d.w. (n = 301). Metal concentrations were greater in Class A than Class B biosolids as a result of biosolids mass reduction, but these levels were substantially lower than regulatory limits. Metal concentrations were (in mg/kg d.w.): As = 6.43 ± 0.400 (n = 141), Cd = 3.39 ± 0.117 (n = 147), Cr = 88.4 ± 2.00 (n = 148), Cu = 401 ± 9.81 (n = 148), Pb = 68.1 ± 2.19 (n = 148), Hg = 1.21 ± 0.116 (n = 148), Mo = 14.9 ± 0.321 (n = 148), Ni = 23.8 ± 0.911 (n = 146), Se = 10.0 ± 0.573 (n = 140), Zn = 778 ± 14.9 (n = 148), K = 850 ± 21.7 (n = 134). In addition, Class A biosolids were rich in total nitrogen (N) and higher in total phosphorus (TP), but low in potassium (K) content. Concentration of K was 850 ± 21.7 mg/kg d.w. (n = 134), TKN was 52,000 ± 13,300 mg/kg d.w. (n = 43), TP was 34,500 ± 6130 mg/kg d.w. (n = 42), and ammonia-N was 7860 ± 1350 mg/kg d.w. (n = 43).

Precipitation thresholds for fecal bacterial indicators in the Chesapeake Bay

Many coastal states of the United States restrict harvest of shellfish from select areas based on some environmental trigger. Such areas are classified as being conditionally approved. In Maryland, the trigger is an inch or more of rainfall that has fallen in the last 24 h. This study used 11 years of monitoring data to test the relationship between daily rainfall totals and densities of fecal indicators in Maryland shellfish harvest waters. Precipitation and fecal coliform (FC) water monitoring data from 2004 to 2014 were matched by date and watershed. The influence of antecedent rainfall conditions (i.e. rainfall in the preceding days or weeks) and the distance of each monitoring station to land were compared to the percent of samples exceeding the FDA criterion for managing shellfish harvest areas. Sample stations beyond 1000m from land had FC densities consistently below the FDA criterion and were excluded from further analysis. Rainfall events greater than an inch tended to result in significantly elevated FC for the following two days, followed by lower levels thereafter. The total amount of rain in the last three weeks was positively related to the proportion of samples with FC greater than the FDA criterion. Bay-wide, the percent of samples exceeding the FDA criterion rose from seven percent for rainfall less than an inch to 37% following one or more inches of rain. Watersheds were classified based on the percent of FC densities over the criterion when rainfall was an inch or more, with 41 of 81 watersheds showing FC responses indicative of potential conditionally approved areas, those shellfish growing areas where the one inch precipitation trigger may be applied. These areas largely overlapped the current conditionally approved areas defined by Maryland. The percent of open water, wetlands, and poorly drained soils explained a significant amount of the variability (R2 = 0.72) in the difference in percent of samples exceeding the FDA criterion when rainfall was greater than an inch and when it was less than an inch. Logistic regression analysis showed that the current trigger of one inch of rain in 24 h is predictive of FC densities over the FDA criterion, though the appropriate threshold will most likely depend on how far the particular shellfish growing area is from land and antecedent rain conditions. In watersheds with relatively high percentages of open water to total watershed size, higher rainfall thresholds might be appropriate. The approach taken in this study could be applied to individual stations and sub-watersheds, potentially allowing the reclassification of some shellfish harvest areas.

Prevalence and diversity of waterborne Arcobacter butzleri in southwestern Alberta, Canada.

Arcobacter butzleri is a potential enteric pathogen to human beings, but its reservoirs and modes of transmission are largely unverified. Microbiological and molecular detection and subtyping techniques can facilitate surveillance of A. butzleri in hosts and environmental reservoirs. We isolated A. butzleri from 173 surface water samples (25.6%) and 81 treated wastewater samples (77.9%) collected in southwestern Alberta over a 1-year period. Arcobacter butzleri isolates (n = 500) were genotyped and compared to determine diversity of A. butzleri in southwestern Alberta. Culture methods affected the frequency of detection and genotype diversity of A. butzleri, and isolation comprehensiveness was different for surface waters and treated wastewaters. Detection of A. butzleri in the Oldman River Watershed corresponded with season, river flow rates, and fecal coliform densities. Arcobacter butzleri was detected most frequently in treated wastewater, in the Oldman River downstream from treated wastewater outfalls, and in tributaries near areas of intensive confined feeding operations. All sample sources possessed high genotype diversity, and A. butzleri isolates from treated wastewaters were genetically similar to isolates from the Oldman River downriver from treated wastewater outfall sites. In southwestern Alberta, municipal and agricultural activities contribute to the density and genotype diversity of A. butzleri in surface waters.

Efficacy of wastewater treatment on Arcobacter butzleri density and strain diversity

Arcobacter butzleri is a suspected waterborne enteric pathogen that is ubiquitous in the environment, but the degree to which wastewater treatment prevents entry of A. butzleri into environmental waters and the risks posed are not well established. Untreated and treated wastewater samples (n = 260) were collected weekly from the Lethbridge and Fort Macleod wastewater treatment facilities (the two major municipal inputs in southwestern Alberta, Canada) from May 2008 to April 2009. Untreated wastewaters contained high densities of A. butzleri and fecal coliform indicators, and densities at Lethbridge were typically higher than at Fort Macleod. Data indicated that A. butzleri and fecal coliform densities in wastewater were greatest in autumn and lowest in winter. Mechanical and biological treatment of wastewaters reduced but did not eliminate fecal coliform indicators or A. butzleri. At Lethbridge, UVB irradiation of mechanically and biologically treated wastewater further reduced densities of fecal coliform indicators. There was high A. butzleri genotype diversity in all sample sources, and survival during treatment was not strain-dependent. No genotype was dominant in any sample source, but 8.9% of genotypes were recurrent over time, and 4.4% of genotypes were detected at both wastewater treatment facilities. The current study demonstrates that viable A. butzleri are able to survive wastewater treatment, including UVB irradiation, which may lead to increased density and genetic diversity of this suspected pathogen in environmental waters via wastewater effluent discharge.

Complete reduction of highly concentrated contaminants in piggery waste by a novel process scheme with an algal-bacterial symbiotic photobioreactor

The complete reduction of highly concentrated contaminants in piggery waste was achieved with an innovative process scheme consecutively combining autothermal thermophilic aerobic digestion (ATAD), an expanded granular sludge bed (EGSB) and a microalgal-bacterial symbiotic vertical photobioreactor (VPBR), followed by biomass recycling for effluent polishing. Contaminants in piggery waste, such as high organic and inorganic matter, total nitrogen (TN), and total phosphorus (TP) contents, were successfully reduced in the newly implemented system. The concentrations of volatile solids (VS) and the chemical oxygen demand (COD) for organic matter in the feed were reduced by approximately 99.3% and 99.7%, respectively, in the innovative system. The overall reduction efficiencies in TN, ammoniacal nitrogen, and TP were 98.8, 98.4, and 93.5%, respectively, through ammonia gas emission, coagulated sludge disposal, and the algal-bacterial symbiotic polishing process. Fecal coliform density was decreased to <1.7 × 104 CFU g−1 total solids. Biogas and CH4 in the EGSB were generated in the range of 0.36–0.79 and 0.18–0.44 L g−1 [VS removed], respectively, and contained 245 ± 19 ppm (v/v) [H2S].

Distributional patterns of fecal indicator bacteria in spring area of Plitvice Lakes National park

Background and purpose: Fecal indicator bacteria (FIB) have widespread use as indicators of water quality and health hazards. The purpose of this study was to determine distributional patterns of FIB and to assess their origin on several sites in spring area and in vertical profile of Proscansko Lake in Plitvice Lakes National Park. Materials and Methods: The study was conducted from March to January 2013 on 9 sampling sites. Standard microbiological methods were used to determine densities of total coliforms (TC), fecal coliforms (FC), fecal streptococcus (FS), Pseudomonas aeruginosa (PS) and Clostridium perfringens in water samples. Results and Conclusions: Source area sustained higher densities of FIB compared to Proscansko Lake, throughout the study period. Sampling site White River below the village had highest values of certain FIB, indicating Plitvicki Ljeskovac as main fecal pollution source. There were seasonal differences in TC and FC with July and October displaying increased densities, the latter probably due to heavy rainfall. The ratio FC/FS in July indicated contamination of mainly animal origin. At the sampling site of Matica River estuary in Proscansko Lake, an increased densities of TC and FC bacteria were observed compared to other sites and depths, possibly due to source streams influence and stratification conditions. This study showed that the indicator bacteria of fecal contamination in the spring area of the Plitvice Lakes National Park are present and their quantity and distribution patterns depend on season, weather conditions and different effects in water column of the lake. Keywords : total coliforms, fecal coliforms, FC/FS ratio, Pseudomonas aeruginosa , source streams, lake, protected area

Distributional patterns of fecal indicator bacteria in spring area of Plitvice lakes National park

Background and purpose: Fecal indicator bacteria (FIB) have widespread use as indicators of water quality and health hazards. The purpose of this study was to determine distributional patterns of FIB and to assess their origin on several sites in spring area and in vertical profile of Prošćansko Lake in Plitvice Lakes National Park. Materials and Methods: The study was conducted from March to January 2013 on 9 sampling sites. Standard microbiological methods were used to determine densities of total coliforms (TC), fecal coliforms (FC), fecal streptococcus (FS), Pseudomonas aeruginosa (PS) and Clostridium perfringens in water samples. Results and Conclusions: Source area sustained higher densities of FIB compared to Prošćansko Lake, throughout the study period. Sampling site White River below the village had highest values of certain FIB, indicating Plitvički Ljeskovac as main fecal pollution source. There were seasonal differences in TC and FC with July and October displaying increased densities, the latter probably due to heavy rainfall. The ratio FC/FS in July indicated contamination of mainly animal origin. At the sampling site of Matica River estuary in Prošćansko Lake, an increased densities of TC and FC bacteria were observed compared to other sites and depths, possibly due to source streams influence and stratification conditions. This study showed that the indicator bacteria of fecal contamination in the spring area of the Plitvice Lakes National Park are present and their quantity and distribution patterns depend on season, weather conditions and different effects in water column of the lake. Keywords: total coliforms, fecal coliforms, FC/FS ratio, Pseudomonas aeruginosa, source streams, lake, protected area

Waste treatment with the pilot scale ATAD and EGSB pig slurry management system followed by sequencing batch treatment

Experiments for highly concentrated contaminants in pig waste slurry were carried out for the feasibility test of a pilot-scale innovative process scheme of engaging autothermal thermophilic aerobic digestion (ATAD) and expended granular sludge bed (EGSB) followed by sequencing batch reactor (SBR) system. Contaminants in pig waste slurry such as organic substance, total nitrogen (TN), ammonia nitrogen and total phosphorus (TP) contents were successfully reduced in the system. Total volatile solids (TVS) and chemical oxygen demands (COD) for organic matter in the feed were 32.92 g/L and 42.55 g/L respectively, and they were reduced by about 98.7% and 99.2%, respectively in the system. The overall removal efficiencies for TN and ammonium nitrogen were found to be 98.1 and 98.5%, respectively. The overall removal efficiency for total phosphorus was also found to be 92.5%. Faecal coliform density was reduced to < 1.2×10 4 CFU/g total solids. Biogas and CH4 were produced in the range of 0.39–0.85 and 0.25–0.62 m 3 /kg [VS removed], respectively. The biogas produced in the system comprised of 295±26 ppm (v/v)

Characterization of residual sand removed from the grit chambers of a wastewater treatment plant and its use as fine aggregate in the preparation of non-structural concrete

This article demonstrates the potential use of residual sand removed from grit chambers, which are used in the primary treatment of Wastewater Treatment Plants (WWTPs), as an alternative material to commercial sand in the production of non-structural concrete in civil construction. The results indicated that the residual sand has a high percentage of total fixed solids (96.9%), high moisture content (14.8%) and significant total coliform [average of 3.84 × 107(100 mL)−1] and fecal coliform densities [average of 5.22 × 105 (100 mL)−1]. The sand cleaning and drying procedure used in the research was effective, since it achieved the following removal efficiencies: about 98.8% of moisture, 67.1% of total volatile solids and 4-log E. coli. After cleaning and drying the residual sand, different amounts of this material were used to prepare the test specimens, which underwent tensile tests. The results of this study confirmed the viable use of residual sand as fine aggregate in concrete for non-structural purposes, and the best performances were verified in tensile and compressive tests (fck) and tensile strength tests (fctk) using 30% (in mass) of the residual sand as fine aggregate (values of 16.6 and 1.60 MPa, respectively).

Determining pathogen and indicator levels in class B municipal organic residuals used for land application.

Biosolids are nutrient-rich organic residuals that are currently used to amend soils for food production. Treatment requirements to inactivate pathogens for production of Class A biosolids are energy intensive. One less energy intensive alternative is to treat biosolids to Class B standards, but it could result in higher pathogen loads. Quantitative microbial risk assessments models have been developed on land application of Class B biosolids but contain many uncertainties because of limited data on specific pathogen densities and the use of fecal indicator organisms as accurate surrogates of pathogen loads. To address this gap, a 12-mo study of the levels and relationships between , , and human adenovirus (HAdV) with fecal coliform, somatic, and F-RNA coliphage levels in Class B biosolids from nine wastewater treatment plants throughout the United States was conducted. Results revealed that fecal coliform, somatic, and F-RNA coliphage densities were consistent throughout the year. More important, results revealed that HAdV ( = 2.5 × 10 genome copies dry g) and ( = 4.14 × 10 cysts dry g) were in all biosolids samples regardless of treatment processes, location, or season. oocysts were also detected (38% positive; range: 0-1.9 × 10 oocysts dry g), albeit sporadically. Positive correlations among three fecal indicator organisms and HAdV, but not protozoa, were also observed. Overall, this study reveals that high concentrations of enteric pathogens (e.g., , , and HAdV) are present in biosolids throughout the United States. Microbial densities found can further assist management and policymakers in establishing more accurate risk assessment models associated with land application of Class B biosolids.

Water quality of the Red River system in the period 2012 - 2013

Few data are available on the quality of Red river water that is used for multi-purposes, including for domestic water demand in some rural areas. This paper presents the observation results of the Red River water quality in two years 2012 and 2013. The monitoring results showed that the average concentrations of nutrients (N, P) were still far lower than the allowed value of the Vietnamese standard limits for surface water quality (QCVN 08:2008/BTNMT, column A2). Due to the impoundment of two big dams in the Da tributary, the suspended solids contents in river water decreased remarkably. The dissolved heavy metal (DHM) concentrations varied in a high range: Cu: 10 – 80 mg.l-1; Zn: 2 – 88 mg.l-1; Cr: 0.2 – 5.1 mg.l-1; Pb: 2 - 107 mg.l-1; Cd: 2 – 12 mg.l-1; Mn: 2 - 35 mg.l-1; and Fe: 160 – 2370 mg.l-1. Most of the mean values of DHM were lower than the allowed values of the QCVN 08:2008/BTNMT, but at several points of time, several DHM (e.g. Fe, Cd, Pb) contents exceeded the allowed values. The Total Coliform (TC) and Fecal Coliform (FC) densities varied in a high range: TC: 23 to 13,000MPN.100ml-1 and FC: 0 to 1,600MPN.100ml-1 and they exceeded the allowed values QCVN 08:2008/BTNMT at several points observed. The dissolved organic carbon (DOC) contents were in low level and the particulate organic carbon (POC) content mainly derived from soil organic leaching and erosion in the basin. The results underlined the need for regularly monitoring the river water quality, and there should be some effective solutions to manage and treat the waste sources in order to provide safe water for different actual purposes use in the Red River basin.&#x0D; Rất ít số liệu sẵn có về chất lượng nước sông Hồng, dòng sông được sử dụng cho nhiều mục đích, bao gồm cả cung cấp nước sinh hoạt ở một số vùng nông thôn. Bài báo trình bày các kết quả quan trắc chất lượng nước sông Hồng trong hai năm 2012 và 2013. Kết quả quan trắc cho thấy chất dinh dưỡng (N, P) thấp xa so với giới hạn cho phép của tiêu chuẩn Việt Nam về chất lượng nước mặt (QCVN 08: 2008/BTNMT cột A2). Do có hai hồ chứa trên sông Đà, hàm lượng chất rắn lơ lửng trong nước sông giảm đáng kể. Các kim loại nặng hòa tan (DHM) có hàm lượng dao động trong khoảng rộng: Cu: 10-80 g.l-1; Zn: 2-88 g.l-1; Cr: 0,2-5,1 g.l-1; Pb: 2-107 g.l-1; Cd: 2-12 g.l-1; Mn: 2-35 g.l-1; và Fe: 160 - 2370 g.l-1. Hầu hết các giá trị trung bình của DHM thấp hơn giá trị cho phép của quy chuẩn QCVN 08: 2008/BTNMT, tuy nhiên, tại một số thời điểm, một số DHM (ví dụ Fe, Cd, Pb) có hàm lượng vượt quá giới hạn cho phép. Mật độ tổng coliform (TC) và coliform phân (FC) dao động trong khoảng rộng: TC: 23 đến 13,000MPN.100ml-1 và FC: 0 đến 1,600MPN.100ml-1 và tại một số thời điểm mật độ TC và FC vượt giá trị cho phép của Quy chuẩn QCVN 08:2008/BTNMT. Hàm lượng cabon hữu cơ hòa tan (DOC) ở mức thấp, và hàm lượng cacbon hữu cơ dạng không tan (POC) chủ yếu có nguồn gốc từ đất rửa trôi và xói mòn trong lưu vực. Kết quả quan trắc nhấn mạnh nhu cầu giám sát thường xuyên chất lượng nước sông, và nên có các giải pháp hiệu quả để quản lý và xử lý các nguồn gây ô nhiễm trong lưu vực nhằm cung cấp nước sạch cho các mục đích sử dụng nước sông Hồng như hiện nay.

Mar Piccolo of Taranto: Vibrio biodiversity in ecotoxicology approach

Microorganisms play an indispensable role in the ecological functioning of marine environment. Some species are sensitive while others are insensitive for a specific pollutant. The aim of this work is a preliminary study of the quantitative and qualitative distribution of cultivable vibrios in sediments and water samples characterized by different toxicity levels. For 1 year, in three suitably selected sampling stations of Mar Piccolo in Taranto (Ionian Sea, Italy), we have evaluated the toxicity level by Microtox® system, vibrios, total, and fecal coliform densities. The results of the Microtox® tests showed sediments characterized by an elevated level of toxicity, while the interstitial water of the same sites always showed biostimulatory phenomenon. The quantitative results show that vibrios and coliforms are more abundant in water than in sediment samples. The most often isolated strains were: Vibrio alginolyticus, Vibrio mediterranei, Vibrio metschinkovii, and Vibrio splendidus II. This work is the first example of study on the distribution of Vibrio species related to toxicity evaluation conducted by the Microtox® bioassay. The results show the different distribution of Vibrionaceae in two environmental matrices analyzed and characterized by different levels of toxicity.

Two-phase anaerobic digestion of partially acidified sewage sludge: a pilot plant study for safe sludge disposal in developing countries

The unsafe disposal of wastewater and sludge in different areas of developing countries results in significant environmental pollution, particularly for groundwater, thus increasing the risk of waterborne diseases spreading. In this work, a two-phase anaerobic digestion process for post-treatment of partially acidified sewage sludge was investigated to evaluate its feasibility as a safe sludge disposal system. Pilot tests showed that an effective sludge stabilization can be achieved (total volatile solids content<65%, organic acid concentration<200 mg/L at flow rate=50 L/d and hydraulic residence time=18 d) as well as a relative low faecal coliform density (<1000 most probable number per g total solids), showing that land application of the sludge without restrictions is possible according to US Environmental Protection Agency criteria for safe sludge disposal. A biogas production as high as 390 L/d with a 60% methane content by volume was achieved, showing that energy production from biogas may be achieved as well.

Pig slurry treatment by a hybrid multi-stage unit system consisting of an ATAD and an EGSB followed by a SBR reactor

Experiments in a laboratory-scale hybrid multi-stage unit system (HMUS) for pig slurry treatment were conducted to demonstrate the feasibility of using autothermal thermophilic aerobic digestion (ATAD), coagulation and expanded granular sludge bed (EGSB) followed by sequencing batch reactor (SBR) system. Contaminants in pig slurry with high organic matter, nitrogen (N) and phosphorus (P) content were almost completely removed in the HMUS. Concentrations of volatile solids (VS) and chemical oxygen demand (COD) were 2.76 and 3.48% respectively, and they were reduced by about 98.9% by the process. The overall nitrogen reduction rates for total nitrogen and ammoniacal nitrogen were 97.9 and 98.3% respectively and were attained through NH 3 gas emission, coagulated sludge disposal and nitrification–denitrification process. The overall phosphorus reduction rate for total phosphorous was 98.2% and this was also attained by coagulation and by the luxury-uptake sludge disposal in the HMUS. Faecal coliform density was reduced to 4 CFU g −1 total solids. The EGSB unit system produced biogas and CH 4 in the range of 0.42–0.86 and 0.21–0.62 m 3 kg −1 [VS removed], respectively. The biogas produced by the HMUS anaerobic digester contained 324 ± 37 ppm (v/v) [H 2 S].

Freeze–thaw treatment of RBC sludge from a remote mining exploration facility in subarctic Canada

Freeze-thaw conditioning of RBC (Rotating Biological Contactor) sludge was tested using a pilot-scale freezing bed placed in a mobile freezer operated at -10°C. Sludge samples from a remote mining exploration facility were flown in every 2 weeks, and added to the freezing bed in 8 layers of 10 cm thick. Approximately 4 months after the first layer of sludge was added, the pilot unit was removed from the freezer and thawed at ambient temperatures. After one day of thawing, the solids concentration increased from 2.6% to 16.2%. The final cake solids concentration was 21%. Melt water had increasing turbidity, COD, TSS, VSS, nitrogen and phosphorus concentrations during the thawing period. Freeze-thaw conditioning also decreased the initial densities of fecal coliforms and Salmonella in sludge. The results of this study showed that freeze-thaw technology successfully dewatered RBC sludge without the need for mechanical equipment, and is a sustainable option for sludge dewatering in cold and remote regions.

Anaerobically digested biosolids odor generation and pathogen indicator regrowth after dewatering

The objective of this research was to investigate whether a preferential stimulation of microorganisms in anaerobically digested biosolids can occur after dewatering and if it can lead to pathogen indicator regrowth and odor generation upon storage. Laboratory incubation simulating biosolids storage indicates that both odorant generation, based on total volatile organic sulfur compound concentrations (TVOSCs) and pathogen indicator regrowth, based on fecal coliform densities follow similar formation and reduction patterns. The formation and reduction patterns of both odor compounds and fecal coliforms imply that groups of microorganism are induced if shearing disturbance is imposed during dewatering, but a secondary stabilization can be achieved soon after 1–2 weeks of storage. The occurrence of the induction is likely the microbial response to substrate release and environmental changes, such as oxygen, resulting from centrifuge shearing. The new conditions favor the growth of fecal coliforms and odor producing bacteria, and therefore, results in the observed fecal coliforms regrowth and odor accumulation during subsequent storage. However, when both substrate and oxygen deplete, a secondary stabilization can be achieved, and both odor and fecal coliforms density will drop.

Estimating changes in river faecal coliform loading using nonparametric multiplicative regression

Faecal coliform (FC) concentration was monitored weekly in the Tangipahoa River over an eight year period. Available USGS discharge and precipitation data were used to construct a nonparametric multiplicative regression (NPMR) model for both forecasting and backcasting of FC density. NPMR backcasting and forecasting of FC allowed for estimation of concentration for any flow regime. During this study a remediation effort was undertaken to improve disinfection systems of contributing municipal waste water treatment plants in the watershed. Time-series analysis of FC concentrations demonstrated a drop in FC levels coinciding with remediation efforts. The NPMR model suggested the reduction in FC levels was not due to climate variance (i.e. discharge and precipitation changes) alone. Use of the NPMR method circumvented the need for construction of a more complex physical watershed model to estimate FC loading in the river. This method can be used to detect and estimate new discharge impacts, or forecast daily FC estimates.

패류 양식장의 세균학적 수질에 미치는 강우의 영향

The impact of rainfall events on the sanitary indicator bacteria density of the shellfish-growing waters in Geoje Bay and Jaran Bay in Korea was investigated. The shellfish-growing area in Geoje Bay, which is a nearly closed basin, was not affected significantly, except near the stream mouth after 11.5 mm of rainfall in 1 day. However, most of the shellfish-growing water in the bay was polluted by fecal coliform bacteria after rain as heavy as 43.0 mm, and the levels of fecal indicator bacteria in some of the sea near the coast did not recover completely until 24 hours after the rainfall. By contrast, in Jaran Bay, which has no significant pollution source in the drainage area, although 9.3-490 MPN/100 mL of fecal coliform bacteria were detected near the stream mouth after rainfall of 33.5 and 81.0 mm, a very low level of the indicator bacteria was detected in the designated shellfish-growing area. During the investigation, the correlations between the sanitary indicator bacteria density and physical parameters, such as salinity and turbidity, were evaluated. Both the total coliform and fecal coliform densities were inversely correlated with salinity. Turbidity was positively correlated with the indicator bacteria density. The survey results suggest that for more efficient management of the shellfish-growing areas located in coastal areas, such as shellfish harvesting after rainfall, a detailed investigation of the effects of rainfall on the bacterial water quality in each growing area is needed.