Hydrodynamic modelling of the microbial water quality in a drinking water source as input for risk reduction management

To mitigate the faecal contamination of drinking water sources and, consequently, to prevent waterborne disease outbreaks, an estimation of the contribution from different sources to the total faecal contamination at the raw water intake of a drinking water treatment plant is needed. The aim of this article was to estimate how much different sources contributed to the faecal contamination at the water intake in a drinking water source, Lake Rådasjön in Sweden. For this purpose, the fate and transport of faecal indicator Escherichia coli within Lake Rådasjön were simulated by a three-dimensional hydrodynamic model. The calibrated hydrodynamic model described the measured data on vertical temperature distribution in the lake well (the Pearson correlation coefficient was 0.99). The data on the E. coli load from the identified contamination sources were gathered and the fate and transport of E. coli released from these sources within the lake were simulated using the developed hydrodynamic model, taking the decay of the E. coli into account. The obtained modelling results were compared to the observed E. coli concentrations at the water intake. The results illustrated that the sources that contributed the most to the faecal contamination at the water intake in Lake Rådasjön were the discharges from the on-site sewers and the main inflow to the lake – the river Mölndalsån. Based on the modelling results recommendations for water producers were formulated. The study demonstrated that this modelling approach is a useful tool for estimating the contribution from different sources to the faecal contamination at the water intake of a drinking water treatment plant and provided decision-support information for the reduction of risks posed to the drinking water source

Temperature-dependent mechanisms of DOM removal by biological activated carbon filters

Seasonal variability in the removal of dissolved organic matter (DOM) by drinking water biological activated carbon (BAC) filters is often attributed to temperature changes. However, it can be rather difficult to directly relate temperature to treatment efficiency at full scale due to seasonal variations in other influential parameters like DOM concentration and character, and microbial activity. Furthermore, processes in BAC filters include adsorption, desorption and biodegradation within biofilms while each respond differently to temperature. This study aimed to decouple these processes by studying the removal of various DOM fractions from coagulated and settled drinking water when in contact with aged (>3 years) BAC filter material at different water temperatures. DOM removal was measured as changes in dissolved organic carbon (DOC), ultraviolet absorbance at 254 nm (UV254) and fluorescence. Under the particular experimental conditions there was little evidence of biological removal; instead, removal of DOM fractions emitting at longer wavelengths ("humic-like", >430 nm) was consistent with chemisorption, removal of DOM emitting at intermediate wavelengths ("humic-like", 390-420 nm) was consistent with physisorption, and multiple mechanisms were indicated for "protein-like" (<380 nm) DOM. Non-biological mechanisms of DOM removal by aged BAC filters are often assumed to be unimportant; however, these results suggest they are important for some DOM fractions, especially during periods of reduced microbial activity

Hepatitis E virus genotype 3 strains and a plethora of other viruses detected in raw and still in tap water

\ua9 2019 The Authors In this study, next generation sequencing was used to explore the virome in 20L up to 10,000L water from different purification steps at two Swedish drinking water treatment plants (DWTPs), and in tap water. One DWTP used ultrafiltration (UF) with 20 nm pores, the other UV light treatment after conventional treatment of the water. Viruses belonging to 26 different families were detected in raw water, in which 6–9 times more sequence reads were found for phages than for known environmental, plant or vertebrate viruses. The total number of viral reads was reduced more than 4-log10 after UF and 3-log10 over UV treatment. However, for some viruses the reduction was 3.5-log10 after UF, as for hepatitis E virus (HEV), which was also detected in tap water, with sequences similar to those in raw water and after treatment. This indicates that HEV had passed through the treatment and entered into the supply network. However, the viability of the viruses is unknown. In tap water 10–130 International Units of HEV RNA/mL were identified, which is a comparable low amount of virus. The risk of getting infected through consumption of tap water is probably negligible, but needs to be investigated. The HEV strains in the waters belonged to subtypes HEV3a and HEV3c/i, which is associated with unknown source of infection in humans infected in Sweden. None of these subtypes are common among pigs or wild boar, the major reservoirs for HEV, indicating that water may play a role in transmitting this virus. The results indicate that monitoring small fecal/oral transmitted viruses in DWTPs may be considered, especially during community outbreaks, to prevent potential transmission by tap water

The UV Dose Used for Disinfection of Drinking Water in Sweden Inadequately Inactivates Enteric Virus with Double-Stranded Genomes

Irradiation with ultraviolet light (UV) at 254 nm is effective in inactivating a wide range of human pathogens. In Sweden, a UV dose of 400 J/m2 is often used for the treatment of drinking water. To investigate its effect on virus inactivation, enteric viruses with different genomic organizations were irradiated with three UV doses (400, 600, and 1000 J/m2), after which their viability on cell cultures was examined. Adenovirus type 2 (double-stranded DNA), simian rotavirus 11 (double-stranded RNA), and echovirus 30 (single-stranded RNA) were suspended in tap water and pumped into a laboratory-scale Aquada 1 UV reactor. Echovirus 30 was reduced by 3.6-log10 by a UV dose of 400 J/m2. Simian rotavirus 11 and adenovirus type 2 were more UV resistant with only 1-log10 reduction at 400 J/m2 and needed 600 J/m2 for 2.9-log10 and 3.1-log10 reductions, respectively. There was no significant increase in the reduction of viral viability at higher UV doses, which may indicate the presence of UV-resistant viruses. These results show that higher UV doses than those usually used in Swedish drinking water treatment plants should be considered in combination with other barriers to disinfect the water when there is a risk of fecal contamination of the water

Skadlig delning av fiske : En studie om FBL 3:8 vid fastighetsbildning

In Swedish law, there is a strong protection for fish conservation applicable to land parcelling as a result of which fishing is divided. The provisions regarding the split of fishing, as found in FBL 3:8, represents a strong public interest and is legally binding for the fishing right holder. In short, this means that a fish right bounded to property may not be divided by land parcelling in a manner that cause problem of any significance for fish conservation. Lantmäteriet in its role as authority shall examine whether the division of fishing causes problems for fish conservation. The purpose of this study was to investigate how the authority interprets and applies FBL 3:8 when dividing fishing. To investigate this, a survey and interview survey was handed out to the authority. The result shows that the number of fish dividing cases differ between surveyors which affects how common they handle FBL 3:8.The study also showed that about every third fish case had not an investigation to FBL 3:8. The application of FBL 3:8 differs by province, but also between every single surveyor. In some areas the surveyors are very restrictive and in some other areas they find dividing of fishing acceptable in certain special situations.Validerat; 20130331 (global_studentproject_submitter

A case study of organic micropollutants in a major Swedish water source - Removal efficiency in seven drinking water treatment plants and influence of operational age of granulated active carbon filters

A wide range of organic micropollutants (n = 163) representing several compound categories (pharmaceuticals, pesticides, per- and polyfluorinated alkyl substances, flame retardants, phthalates, food additives, drugs and benzos) were analysed in water samples from the Gota Alv river (Sweden's second largest source water). The sampling also included raw water and finished drinking water from seven drinking water treatment plants and in addition a more detailed sampling at one of the treatment plants after six granulated active carbon filters of varying operational ages. In total, 27 organic micropollutants were detected, with individual concentrations ranging from sub ng L-1 levels to 54 ng L-1. The impact of human activities along the flow path was reflected by increased concentrations downstream the river, with total concentrations ranging from 65 ng L-1 at the start of the river to 120 ng L-1 at the last sampling point. The removal efficiency was significantly (p = 0.014; one-sided t-test) higher in treatment plants that employed granulated active carbon filters (n = 4; average 60%) or artificial infiltration (n = 1; 65%) compared with those that used a more conventional treatment strategy (n = 2; 38%). The removal was also strongly affected by the operational age of the carbon filters. A filter with an operational age of 12 months with recent addition of-10% new material showed an average removal efficiency of 92%, while a 25-month old filler had an average of 76%, and an even lower 34% was observed for a 71-month old filter. The breakthrough in the carbon filters occurred in the order of dissolved organic carbon, per- and polyfluorinated alkyl substances and then other organic micropollutants. The addition of fresh granulated active carbon seemed to iimprove the removal of hydrophobic organic compounds, particularly dissolved organic carbon and per- and polyfluorinated alkyl substances. (C) 2019 The Authors. Published by Elsevier B.V

F\uf6rnyelseplanering av vatten- och avloppsf\uf6rs\uf6rjningsn\ue4t i 18 svenska kommuner

The water and wastewater pipe net management is of considerable interest. The management influences risk for distribution interruption, health disruptions and environmental safe sewer discharge. There are also huge values involved. The renewal of the pipe networks is the major question, each municipality has to handle. There is a lot of knowledge among the water administrations in the municipalities; however the knowledge is often in the mind of the employees. Water engineers in 18 Swedish municipalities of various categories have been interviewed. Most municipalities are in short of a systematic renewal planning, such as risk analysis or cost calculated goals. The interviewed municipalities felt that there renewal rate should be higher, but they have no structural instrument to show the reasons. Priorities were done as “worst first”, and the selection of “worst” were built on experience. There is a need of structure in order to assist the municipalities to rely on their work, and to express to politicians and others the future rehabilitation needs

Time distributed associations between rainfall, raw water quality and gastrointestinal illness

Samband beskrivs mellan kraftigt regn, försämrad råvattenkvalitet och det ett ökat antal fall av magsjuka där den tidsmässiga fördröjningen överensstämmer med inkubationstider gällande virus. Rapporten förslår att ett bättre skydd mot förorening av Göta älv och förbättrade barriärer i dricksvattenproduktionen är motiverade.Relations described between heavy rainfall, poor raw water quality and an increased number of cases of gastroenteritis in which the temporal delay is consistent with the incubation times of viruses. The report suggests that better protection against pollution in the river Göta Älv and improved barriers in drinking water production are justified.Projektets finansiering:Svenskt Vatten Utveckling, FormasKlimatförändringar, råvattenkvalitet, rening och distribution – bedömning av mikrobiella risker genom hälsostudie

Hydrodynamic modelling and forecasting of microbial water quality in a drinking water source

Faecal contamination often enters drinking water sources through emergency discharges, which occur as a result of technical malfunctions or a hydraulic overload of the sewer system during periods of heavy rain. In October–November 2012, several emergency discharges entered Lake R\ue5dasj\uf6n – a drinking water source for Gothenburg, Sweden. To describe and forecast the influence of these emergency discharges on the microbial water quality, the spread of Escherichia coli (E. coli) within the lake was simulated using a three-dimensional hydrodynamic model. The model was run for a period of four months using the observed data, and for a period of 9 days using meteorological forecast data. The modelling results showed how much every contamination source contributed to the total E. coli concentrations at the water intakes. The agreement between the modelling results and the measured concentrations was satisfactory. The results of this study led to the decision to use the lake for drinking water production. This study demonstrated that the proposed modelling approach can be used to provide short-term forecasts of the microbial water quality in drinking water sources

Fault tree analysis for integrated and probabilistic risk analysis of drinking water systems

Drinking water systems are vulnerable and subject to a wide range of risks. To avoid sub-optimisation of risk-reduction options, risk analyses need to include the entire drinking water system, from source to tap. Such an integrated approach demands tools that are able to model interactions between different events. Fault tree analysis is a risk estimation tool with the ability to model interactions between events. Using fault tree analysis on an integrated level, a probabilistic risk analysis of a large drinking water system in Sweden was carried out. The primary aims of the study were: (1) to develop a method for integrated and probabilistic risk analysis of entire drinking water systems; and (2) to evaluate the applicability of Customer Minutes Lost (CML) as a measure of risk. The analysis included situations where no water is delivered to the consumer (quantity failure) and situations where water is delivered but does not comply with water quality standards (quality failure). Hard data as well as expert judgements were used to estimate probabilities of events and uncertainties in the estimates. The calculations were performed using Monte Carlo simulations. CML is shown to be a useful measure of risks associated with drinking water systems. The method presented provides information on risk levels, probabilities of failure, failure rates and downtimes of the system. This information is available for the entire system as well as its different sub-systems. Furthermore, the method enables comparison of the results with performance targets and acceptable levels of risk. The method thus facilitates integrated risk analysis and consequently helps decision-makers to minimise sub-optimisation of risk-reduction options