Predicting wastewater temperatures in sewer pipes using abductive network models.

A predictive modelling technique was employed to estimate wastewater temperatures in sewer pipes. The simplicity of abductive predictive models attracts large numbers of users due to their minimal computation time and limited number of measurable input parameters. Data measured from five sewer pipes over a period of 12 months provide 33,900 training entries and 39,000 evaluation entries to support the models' development. Two simple predictive models for urban upstream combined sewers and large downstream collector sewers were developed. They delivered good correlation between measured and predicted wastewater temperatures proven by their R(2) values of up to 0.98 and root mean square error (RMSE) of the temperature change along the sewer pipe ranging from 0.15 °C to 0.33 °C. Analysis of a number of potential input parameters indicated that upstream wastewater temperature and downstream in-sewer air temperature were the only input parameters that are needed in the developed models to deliver this level of accuracy.

Modelling the viability of heat recovery from combined sewers.

Modelling of wastewater temperatures along a sewer pipe using energy balance equations and assuming steady-state conditions was achieved. Modelling error was calculated, by comparing the predicted temperature drop to measured ones in three combined sewers, and was found to have an overall root mean squared error of 0.37 K. Downstream measured wastewater temperature was plotted against modelled values; their line gradients were found to be within the range of 0.9995-1.0012. The ultimate aim of the modelling is to assess the viability of recovering heat from sewer pipes. This is done by evaluating an appropriate location for a heat exchanger within a sewer network that can recover heat without impacting negatively on the downstream wastewater treatment plant (WWTP). Long sewers may prove to be more viable for heat recovery, as heat lost can be reclaimed before wastewater reaching the WWTP.

Erosion resistance and behaviour of highly organic in-sewer sediment.

Reliable prediction of time-varying pollutant loads in combined sewer systems during storm periods can aid better management of the release of pollution into natural environments as well as enhancing storage tank design. Better understanding of the behaviour of sewer sediments is crucial for the development of models that adequately describe the transport of in-sewer solids and accurately predict the changes in pollutant concentration within combined sewers during storm events. This paper reports on the results of a test programme to examine the erosion of highly organic sewer sediment under the application of time-varying shear stress. The tests were carried out with and without supplying oxygen, and varying simulated dry-weather periods. The aim was to investigate the behaviour of real in-sewer sediment with a high organic content (around 80%) in an attempt to improve prediction of the transport rates under the particular Mediterranean conditions of long dry-period/build-up and intense rainfall/wash-off, and understand how this environment affects the erosional resistance and subsequent sediment release. Results have been compared with previous work on lower organic content sewer sediments and artificial organic sediment.

Predictors of return to work and employment in cancer survivors: a systematic review.

The objective of this study was to provide an overview of the prognostic factors for return to work and employment of cancer survivors. Cohort studies were selected if the population consisted of cancer patients between 18 and 65 years of age, with return to work, employment or equivalent concepts as main outcome measure, studying at least one prognostic factor. The methodological quality of the included studies and level of evidence for each prognostic factor were assessed. Twenty-eight cohort studies met the inclusion criteria. Heavy work and chemotherapy were negatively associated with return to work. Less invasive surgery was positively associated with return to work. Breast cancer survivors had the greatest chance of return to work. Old age, low education and low income were negatively associated with employment. Moderate evidence was found for extensive disease being negatively associated with both return to work and employment, and for female gender being negatively associated with return to work. The review shows that in cancer survivors, a limited number of prognostic factors of return to work and employment can be identified. Physicians primarily engaged in the process of vocational rehabilitation of cancer survivors should be aware of the potential role these factors exert.

Development and reliability of performance indicators for measuring adherence to a guideline for depression by insurance physicians.

INTRODUCTION: We wanted to measure adherence to the guideline for depression in disability assessments. The research questions we addressed were: How can we develop performance indicators (PIs) for adherence to the Dutch guideline for disability assessment of patients with depression and how can we measure the quality of the scores? What is the inter-rater reliability of these PIs? What is the quality of the PI scores? METHODS: PIs, developed by the researchers, were reviewed on various aspects, by a panel of seven experts in several consulting rounds. After adjustments, senior insurance physicians (IPs) attended two training sessions and scored the PIs on 10 different simulated case reports. Two researchers developed proxy 'gold standard' scores for these 10 case reports. To assess the inter-rater reliability and the quality of the scores, we calculated the intra-class correlations (ICC) and 95% confidence intervals (CI) of the PI scores and of the PI scores compared to the proxy 'gold standard', respectively. RESULTS: Six specific and relevant PIs resulted from the consultation of the panel of experts. The PI scores for the 10 case reports, rated by seven (of the eight) senior IPs who completed both training sessions, showed that the PIs were not reliable at individual level (ICC = 0.543; 95% CI 0.426-0.642). However, the ICC became more reliable as an average of two raters was calculated (ICC = 0.704). The ICC of the PI scores with the proxy 'gold standard' was 0.538 (95% CI 0.419-0.640), but the quality was higher when calculated as an average of two raters (ICC = 0.700). CONCLUSION: The PIs for adherence to the guideline were sufficiently reliable, and the quality of their scores was adequate if at least two well-trained raters were involved. The senior IPs evaluated the feasibility of the PIs as good, with a prerequisite of sufficient training. This method may be interesting for measuring guideline adherence and quality of disability assessments in general.

Resuming work after cancer: a prospective study of occupational register data.

INTRODUCTION: Long-term employment rates have been studied in cancer survivors, but little is known about the return to work of cancer patients. This study investigated return to work (RTW) within 2 years after the diagnosis of different types of cancer. METHODS: This prospective study investigated the associations of demographics (age, gender, socioeconomic status, and residential region) and occupational factors (occupation, duration of employment, and company size) of employees absent from work due to cancer with the time to partial RTW, defined as working at least 50% of the earnings before sickness absence. Likewise, the associations of demographics and occupational factors with full RTW at equal earnings as before sickness absence were investigated. RESULTS: The cohort included 5,234 employees who had been absent from work due to cancer between January 2004 and December 2006. The time to partial RTW was shortest among employees with skin cancer (median 55 days) and longest among employees with lung cancer (median 377 days). There were no significant associations between RTW and demographics. With regard to the occupational factors, employees in high occupational classes started working earlier than those in low occupational classes, but the time to full RTW did not differ significantly across occupational classes. Employees working in large companies returned to work earlier than those working in small companies. CONCLUSION: RTW after different types of cancer depended on occupational factors rather than demographics.

A typology of sick-listed claimants to improve communication skills for social insurance physicians during medical disability assessment interviews.

INTRODUCTION: Role play with standardised simulated patients is often included in communication training. However, regarding physician-patient encounters in medical disability assessment interviews it is unclear what should be included in the scenarios for actors. The first objective of this study was to determine which types of medical disability claimants can be distinguished based on behavioural determinants. The second objective was to determine if these types of claimants differed in their perception of communication behaviour and their satisfaction with the communication with physicians. METHODS: Questionnaire data were collected from 56 Dutch claimants for 13 behavioural determinants before their assessment interview, and for 12 behavioural and satisfaction variables afterwards. For the first objective cluster analyses were performed and for the second objective linear regression analyses were performed. RESULTS: The results showed that three types of claimants could be distinguished: insecure support-seeking claimants, confident claimants, and socially isolated claimants. Overall, claimants were positive about the communication with the physician: insecure support-seeking claimants were satisfied and confident claimants were highly satisfied, but socially isolated claimants were unsatisfied. CONCLUSION: Scenarios for standardised simulated patients should include different types of claimants. In training, special attention should be given to communication with socially isolated claimants.

Stereotyping of medical disability claimants' communication behaviour by physicians: towards more focused education for social insurance physicians.

BACKGROUND: Physicians who hold medical disability assessment interviews (social insurance physicians) are probably influenced by stereotypes of claimants, especially because they have limited time available and they have to make complicated decisions. Because little is known about the influences of stereotyping on assessment interviews, the objectives of this paper were to qualitatively investigate: (1) the content of stereotypes used to classify claimants with regard to the way in which they communicate; (2) the origins of such stereotypes; (3) the advantages and disadvantages of stereotyping in assessment interviews; and (4) how social insurance physicians minimise the undesirable influences of negative stereotyping. METHODS: Data were collected during three focus group meetings with social insurance physicians who hold medical disability assessment interviews with sick-listed employees (i.e. claimants). The participants also completed a questionnaire about demographic characteristics. The data were qualitatively analysed in Atlas.ti in four steps, according to the grounded theory and the principle of constant comparison. RESULTS: A total of 22 social insurance physicians participated. Based on their responses, a claimant's communication was classified with regard to the degree of respect and acceptance in the physician-claimant relationship, and the degree of dominance. Most of the social insurance physicians reported that they classify claimants in general groups, and use these classifications to adapt their own communication behaviour. Moreover, the social insurance physicians revealed that their stereotypes originate from information in the claimants' files and first impressions. The main advantages of stereotyping were that this provides a framework for the assessment interview, it can save time, and it is interesting to check whether the stereotype is correct. Disadvantages of stereotyping were that the stereotypes often prove incorrect, they do not give the complete picture, and the claimant's behaviour changes constantly. Social insurance physicians try to minimise the undesirable influences of stereotypes by being aware of counter transference, making formal assessments, staying neutral to the best of their ability, and being compassionate. CONCLUSIONS: We concluded that social insurance physicians adapt their communication style to the degree of respect and dominance of claimants in the physician-claimant relationship, but they try to minimise the undesirable influences of stereotypes in assessment interviews. It is recommended that this issue should be addressed in communication skills training.

Towards quantification of uncertainty in predicting water quality failures in integrated catchment model studies.

This paper describes the development and application of a method for estimating uncertainty in the prediction of sewer flow quantity and quality and how this may impact on the prediction of water quality failures in integrated catchment modelling (ICM) studies. The method is generic and readily adaptable for use with different flow quality prediction models that are used in ICM studies. Use is made of the elicitation concept, whereby expert knowledge combined with a limited amount of data are translated into probability distributions describing the level of uncertainty of various input and model variables. This type of approach can be used even if little or no site specific data is available. Integrated catchment modelling studies often use complex deterministic models. To apply the results of elicitation in a case study, a computational reduction method has been developed in order to determine levels of uncertainty in model outputs with a reasonably practical level of computational effort. This approach was applied to determine the level of uncertainty in the number of water quality failures predicted by an ICM study, due to uncertainty associated with input and model parameters of the urban drainage model component of the ICM. For a small case study catchment in the UK, it was shown that the predicted number of water quality failures in the receiving water could vary by around 45% of the number predicted without consideration of model uncertainty for dissolved oxygen and around 32% for unionised ammonia. It was concluded that the potential overall levels of uncertainty in the ICM outputs could be significant. Any solutions designed using modelling approaches that do not consider uncertainty associated with model input and model parameters may be significantly over-dimensioned or under-dimensioned. With changing external inputs, such as rainfall and river flows due to climate change, better accounting for uncertainty is required.

Can cross country differences in return-to-work after chronic occupational back pain be explained? An exploratory analysis on disability policies in a six country cohort study.

INTRODUCTION: There are substantial differences in the number of disability benefits for occupational low back pain (LBP) among countries. There are also large cross country differences in disability policies. According to the Organization for Economic Cooperation and Development (OECD) there are two principal policy approaches: countries which have an emphasis on a compensation policy approach or countries with an emphasis on an reintegration policy approach. The International Social Security Association initiated this study to explain differences in return-to-work (RTW) among claimants with long term sick leave due to LBP between countries with a special focus on the effect of different disability policies. METHODS: A multinational cohort of 2,825 compensation claimants off work for 3-4 months due to LBP was recruited in Denmark, Germany, Israel, the Netherlands, Sweden, and the United States. Relevant predictors and interventions were measured at 3 months, one and 2 years after the start of sick leave. The main outcome measure was duration until sustainable RTW (i.e. working after 2 years). Multivariate analyses were conducted to explain differences in sustainable RTW between countries and to explore the effect of different disability policies. RESULTS: Medical and work interventions varied considerably between countries. Sustainable RTW ranged from 22% in the German cohort up to 62% in the Dutch cohort after 2 years of follow-up. Work interventions and job characteristics contributed most to these differences. Patient health, medical interventions and patient characteristics were less important. In addition, cross-country differences in eligibility criteria for entitlement to long-term and/or partial disability benefits contributed to the observed differences in sustainable RTW rates: less strict criteria are more effective. The model including various compensation policy variables explained 48% of the variance. CONCLUSIONS: Large cross-country differences in sustainable RTW after chronic LBP are mainly explained by cross-country differences in applied work interventions. Differences in eligibility criteria for long term disability benefits contributed also to the differences in RTW. This study supports OECD policy recommendations: Individual packages of work interventions and flexible (partial) disability benefits adapted to the individual needs and capacities are important for preventing work disability due to LBP.

Estimation of uncertainty in long term combined sewer sediment behaviour predictions, a UK case study.

There are regulatory driven requirements for UK water companies to reduce the number of properties at risk of sewer flooding. One of the potential causes of sewer flooding is the presence of persistent sediment deposits in sewers. This is a common problem in many combined sewers. Although the regulation is risk based, there is a gap in current knowledge on how risk assessment is affected by the uncertainty in sewer solids behaviour prediction. This paper describes a UK case study exploring the possibility of estimating uncertainty in sewer sediment deposit level predictions, using Monte Carlo simulations combined with a response database.

Detailed observation and measurement of sewer sediment erosion under aerobic and anaerobic conditions.

A greater understanding of the erosion behaviour of sewer sediments is necessary in order to reliably estimate the amount and nature of the sewer sediments released from deposits in sewers and transported either to waste water treatment plants or discharged into the environment. Research has indicated that microbial activity in sediment can influence the physical release of sediment from in-pipe deposits. This paper reports on a series of erosion tests in which sewer sediments from different sewer networks are kept under different environmental conditions and their resistance to erosion is examined. The erosion tests are carried out under aerobic and anaerobic conditions and two temperatures, one representing ambient sewer temperatures and a lower temperature that significantly suppresses bacterial activity.

The acoustic attenuation and hydraulic roughness in a large section sewer pipe with periodical obstacles.

The acoustic attenuation, relative sound pressure levels and the equivalent Nikuradse wall roughness under variable flow conditions in a 600 mm concrete sewer pipe are experimentally investigated. The values of the acoustic attenuation are obtained in the case of airborne sound propagation in the dry pipe. A range of values of the equivalent wall roughness is artificially generated by deploying a periodical array of engineering bricks. A novel method of rapid evaluation of the acoustic attenuation is proposed. The method relies upon sound reflections from the adjacent manholes. The results demonstrate that the acoustic attenuation depends strongly on the value of the equivalent wall roughness. This work can pave the way to the efficient methodology for the in-situ, physical evaluation of the equivalent hydraulic roughness of new and existing sewer networks.