Surface water sewer misconnections in England and Wales: Pollution sources and impacts.

In urban areas served by separate sewerage consisting of separate pipe systems it is not uncommon for misconnections to be made either accidentally or deliberately, whereby the wrong effluent is connected to the wrong sewer. The main focus of this problem has been on in-household appliances that are wrongly connected to separate surface water sewers, potentially leading to pollution of receiving waters and non-compliance with statutory water quality standards. This paper examines the available evidence to evaluate the potential scale, severity and cost of the problem in England and Wales in comparison to that reported from investigations in the United States. The particular difficulties associated with distinguishing specific sewage sources in the wastewater "cocktail" discharged at polluted surface water outfalls are reviewed. The deficiencies of existing legislation and enforcing compliance with respect to misconnections are also discussed and the pollution potential resulting from domestic misconnections is explored based on sampled data.

The management of urban surface water flood risks: SUDS performance in flood reduction from extreme events.

The need to improve the urban drainage network to meet recent urban growth and the redevelopment of old industrial and commercial areas provides an opportunity for managing urban surface water infrastructure in a more sustainable way. The use of sustainable urban drainage systems (SUDS) can reduce urban surface water flooding as well as the pollution impact of urban discharges on receiving waters. However, these techniques are not yet well known by many stakeholders involved in the decision-making process, or at least the evidence of their performance effectiveness may be doubted compared with more traditional engineering solutions often promoted by existing 1D/2D drainage models. The use of geographic information systems (GIS) in facilitating the inter-related risk analysis of sewer surface water overflows and urban flooding as well as in better communication with stakeholders is demonstrated in this paper. An innovative coupled 1D/2D urban sewer/overland flow model has been developed and tested in conjunction with a SUDS selection and location tool (SUDSLOC) to enable a robust management approach to surface water flood risks and to improve the resilience of the urban drainage infrastructure. The paper demonstrates the numerical and modelling basis of the integrated 1D/2D and SUDSLOC approach and the working assumptions and flexibility of the application together with some limitations and uncertainties. The role of the SUDSLOC modelling component in quantifying flow, and surcharge reduction benefits arising from the strategic selection and location of differing SUDS controls are also demonstrated for an extreme storm event scenario.

Risk prioritisation of stormwater pollutant sources.

This paper describes the development of a pollutant risk prioritisation methodology for the comparative assessment of stormwater pollutants discharged from differing land use types and activities. Guidelines are presented which evaluate available data with respect to 'likelihood of occurrence' and 'severity of impact'. The use of the developed approach is demonstrated through its application to total suspended solids, biochemical oxygen demand, lead and cadmium. The proposed benchmarking scheme represents a transparent and auditable mechanism to support the synthesis of data from a variety of sources and is sufficiently flexible to incorporate the use of chemical, physical and/or ecological data sets. Practitioners involved in developing and implementing pollutant mitigation programmes are assisted in two key ways. Firstly through enabling the risks to receiving waters from diffuse pollution on a source-by-source and/or pollutant-by-pollutant basis at a catchment scale to be comparatively assessed and prioritised. Secondly, the methodology informs the selection of appropriate diffuse pollution control strategies.

Antiviral pandemic risk assessment for urban receiving waters.

An 80% metabolic conversion of the Tamiflu pro-drug (oseltamivir phosphate, OP) to its metabolite oseltamivir carboxylate (OC) and a high excretion rate combined with poor removal at sewage treatment works (STWs) means that potentially high STW OC emissions may occur in receiving waters. A risk assessment approach undertaken within the River Lee catchment in North East London indicates that predicted environmental concentrations for surface waters (PEC(sw)) are likely to be in the general range of 40-80 microg L(-1) during a pandemic sitaution within urban catchments having low dilution capacities. This implies low risk exposure levels which confirms previous studies, but there are considerable uncertainties associated with the methodology as well as risks that might result from persistent, long term chronic exposure to low-level water and sediment concentrations which might be mobilised under subsequent extreme flow conditions.

Sewer exfiltration and the colmation layer.

Sewer rig studies demonstrate a rapid exponential decline in exfiltration rates from gaps and joints to establish an ultimate steady-state equilibrium varying between 10(-3)-10(-6) l s(-1), with minimum average daily rates per standardised leak area and sewer length varying between 0.02-9.0 l d(-1)cm(-2) and 0.0002-2.0 l s(-1) km(-1) respectively. These loss rates are much larger than those derived from indirect monitoring/modelling studies which suggest losses between 1.4 x 10(-5)-0.179 l s(-1) km(-1). The confusion regarding conflicting definitions of the colmation, transition, bridging and biofilm layers is addressed, and the significance of these clogging layers in terms of both hydraulic and matrix potential on the exfiltration loss is evaluated. The influence of variability and instability of flow and bed turbulence on determining critical leakage conditions following the onset of equilibrium steady-state is assessed. This challenges the generally held assumption that elevated head pressure condition alone is a necessary precursor for rupture of the clogging layers.

Defining urban diffuse pollution loadings and receiving water hazard.

The use of unit area loading approaches to address the requirements of the US Clean Water Act (CWA) and the EU Water Framework Directive (WFD) to identify and manage diffuse urban pollution sources is outlined. Issues relating to traditional volume-concentration probabilistic modelling are highlighted and the robustness of total maximum daily load (TMDL) approaches is discussed. A hazard assessment methodology for catchment scale identification of source area pollutant loadings and receiving water ecological impacts is developed based on urban land use activities.

Towards a better understanding of sewer exfiltration.

This paper gives a full review of the importance of sewer leakage, which has received increased attention throughout the last decades. Despite the intensive interdisciplinary research that has been invested, its magnitude is still unclear and a comprehensive solution for the assessment of sewer exfiltration does not seem to be at hand. However, given that mechanisms of exfiltration and the factors influencing its extent are similar all over the world, it seems possible to develop a generic leakage approach. Several methods for modelling sewer leakage are reviewed and the available measuring techniques are critically evaluated. Based on this evaluation, we suggest a unifying framework to facilitate focused model building. Specifically, we identify open research questions and propose to (i) standardise measurement results to enable better understanding, (ii) perform more long-term experiments under realistic field conditions, and (iii) assess the uncertainty of measurement and model results so that findings are not over-interpreted.

Highway filter drain waste arisings: a challenge for urban source control management?

Essential maintenance activities on highway BMP drainage controls involve refurbishment of filter (French) drains which can generate substantial amounts of "controlled waste". An innovative procedure for their re-instatement is described which offers a more sustainable option for filter drain/trench management. The quality classification of these waste arisings is problematical and it is difficult to reliably identify the risks posed by such materials and the most effective forms of management and disposal options.

Pharmaceutical and personal care products (PPCPs) in urban receiving waters.

The transport pathways of pharmaceutical and personal care products (PPCP) discharges within the urban water cycle include both combined and separate sewer systems with only the former receiving treatment. The dry-weather flow dilution patterns for selected PPCPs following discharge from a sewage treatment works (STW) to a North London stream indicate a persistent downstream increase in concentration. The dilution ratio analysis also indicates that the STW's final effluent only contributes a dilution of the endogenous concentrations already present in the river flow which reflects a progressive PPCP load with increasing urbanization; "worst-case" scenarios being probably related to wet-weather conditions. Maximum PPCP concentrations fall above the reported PEC levels and the analysis highlights the deficiencies of conventional acute toxicity for the evaluation of long-term effects of episodic urban discharges. Groundwater analysis points to sewer exfiltration which is limited in terms of PPCP impact to 25-50 cm depths.

Constructed wetlands in UK urban surface drainage systems.

This paper presents the outcome of an inventory of planted wetland systems in the UK which are classified according to land use type and are all examples of sustainable drainage systems. The introduction of constructed wetlands to treat surface runoff essentially followed a 1997 Environment Agency for England and Wales report advocating the use of "soft engineered" facilities including wetlands in the context of sustainable development and Agenda 21. Subsequently published reports by the UK Construction Industry Research and Information Association (CIRIA) have promoted the potential benefits to both developer and the community of adopting constructed wetlands and other vegetated systems as a sustainable drainage approach. In addition, the UK Environment Agency and Highways Agency (HA) have recently published their own design criteria and requirements for vegetative control and treatment of road runoff. A case study of the design and performance of a constructed wetland system for the treatment of road runoff is discussed. The performance of these systems will be assessed in terms of their design criteria, runoff loadings as well as vegetation and structure maintenance procedures. The differing design approaches in guidance documents published in the UK by the Environment Agency, CIRIA and HA will also be evaluated.

Factors influencing exfiltration processes in sewers.

Exfiltration from sewers is widespread and emerging legislation may require water service providers to identify, and rectify, its sources in sewerage systems. This paper describes exfiltration test apparatus and a series of experiments undertaken using sewage to gain a better understanding of the influence of sewage solids and sediments on leakage rates. An overview of the results obtained is given, which demonstrates that most previous estimates of exfiltration leakage rates were too high due to a lack of appreciation of the "self-repairing" action of sewage and sewage associated solids. Exfiltration rates of 0.1% of the sewer flow or 0.001 I/s have been recorded for defects up to 6 mm wide.

Multicriteria decision approaches to support sustainable drainage options for the treatment of highway and urban runoff.

The control and treatment of urban and highway runoff involves a variety of stakeholders in the selection of sustainable drainage systems (SUDS) as the design process needs to consider not only water quantity but also water quality and amenity. Thus, technical, environmental/ecological, social/community and economic cost factors become prime potential sustainability criteria in terms of assessing long-term, cost-effective drainage options. The paper develops a multicriteria analysis methodology for the evaluation and accreditation of SUDS structures within the context of an overall decision-support framework. Approaches independently developed in the UK and France are outlined with the common multicriteria structures defining generic performance criteria together with supporting benchmark standards and exclusion thresholds. A French case study is presented to illustrate the approach and to highlight the inherent constraints and subjectivity embedded in the decision-making process.

Experimental studies of sewer exfiltration.

The effects of joint openings and in-pipe sediment on exfiltration losses in an experimental sewer are reported and the influence of flow and head on loss rates are also evaluated. Exfiltration rates tend to be exponential with changes in head for clean-water tests but exhibit power functions when the pipe is subject to sedimentation. In-pipe sediment leads to an effective sealing of joints especially if the invert deposits are both organic in nature and contain saturated adhesive material such as shredded toilet tissue. Simple tracer techniques are described to quantify exfiltration losses and the potential effects of tracer adsorption by pipe solids are evaluated.

Sewer losses and interactions with groundwater quality.

Inflow/infiltration (I/I) and infiltration/exfiltration (I/E) are interactive processes which dynamically affect sewer and groundwater performance. The incidence and condition of "critical" sewers in the UK are identified together with chemical and bacterial methods of quantifying I/E and its potential impact on sewer performance and on urban groundwater pollution. Whilst the impacts of I/E do not appear to be substantial on the basis of existing evidence, some caution is advocated in respect of long term sewer sustainability.

Parents' perceptions of their children's death concept.

To examine the differences between parents' and nonparents' beliefs regarding the concept of death in children, 352 individuals answered a demographic survey. Questions concerning beliefs about the age at which children develop the concept of the irreversibility of death were included on the survey. Parents believed that the concept is developed at an earlier age than did nonparents, and also believed that the concept is developed at an earlier age than has been revealed by most research.

Risk assessment approaches for ecosystem responses to transient pollution events in urban receiving waters.

Alternative risk assessment approaches are reviewed for the evaluation of the ecological status and health of urban receiving waters subject to intermittent pollution events. Performance-based criteria founded on exceedance probabilities and related to the end-of-pipe discharge of chemical-specific substances comprise the conventional basis for setting regulatory standards in both North America and Europe. The difficulties and limitations of this approach, particularly in identifying realistic chronic, sub-lethal toxic risks arising from complex effluents are discussed. The potential role of Toxicity Based Criteria (TBC) for setting ecological consent limits for stormwater effluents is considered and the capabilities and limitations of Direct Toxicity Assessment (DTA) are identified. The inability of DTA procedures to satisfactorily evaluate chronic, sub-lethal risks has led to increasing interest in the potential use of in-situ biomarker techniques for the fingerprinting of stress-response properties as a means of diagnosing risk assessment for integrated urban runoff management.

The treatment of systemic candidiasis in neonates with oral fluconazole.

Fungal septicaemia has become a frequent problem in neonatal intensive care units. The usual treatment for this condition, amphotericin B alone or in combination with 5-fluorocytosine, is sometimes unsatisfactory, especially in neonates. We report our experience of fluconazole in neonates. Neonates who developed Candida septicaemia in the neonatal unit of Ga-Rankuwa Hospital (MEDUNSA) over a 1-year period were treated with oral fluconazole. The diagnosis was based on fungal cultures obtained from sites which are normally sterile. Blood cultures and renal, haematological and liver functions were monitored regularly. Therapy was continued for at least 1 week after the first negative culture was obtained. Twenty-one neonates were treated; the clinical and microbiological cure rate was 90.5%. No serious renal, haematological or hepatic complications were detected; mild hepatotoxicity was evidenced by elevated enzymes in a third of the children. Relapse occurred in one baby who received inadequate doses of fluconazole. Two babies died of causes unrelated to a systemic fungal infection. We conclude that fluconazole may be a safe and effective alternative for the management of systemic candidiasis in neonates. A comparative trial is necessary.

Fluconazole vs. amphotericin B for the treatment of neonatal fungal septicemia: a prospective randomized trial.

OBJECTIVE: Fungal septicemia is a devastating disease in the neonate, especially in the low birth weight preterm infant who is especially vulnerable to disseminated fungal sepsis. The objective of this study was to compare the efficacy, safety and overall convenience of fluconazole vs. amphotericin B for the treatment of disseminated fungal sepsis in neonates. DESIGN: A prospective, randomized, collaborative study conducted at two South African neonatal units. SUBJECTS: Twenty-four infants with proven fungal septicemia were treated from June, 1992, to June, 1993. Twelve received fluconazole, 11 received amphotericin B and 1 was excluded. Assessment of hepatic, renal and hematologic functions were performed before, during and after treatment. The two groups were comparable at the time of enrollment into the study. RESULTS: Infants receiving amphotericin B had significantly higher values of total and direct bilirubin and alkaline phosphatase values at the end of treatment, while the fluconazole group showed a significant increase in the platelet count. The cumulative total numbers of days receiving intravenous therapy for the administration of antifungal drugs were 57 for the fluconazole group and 162 for the amphotericin group; no central lines were needed in the fluconazole group, whereas 3 babies given amphotericin B had central catheters for a cumulative total of 27 days. The case fatality rate was 33% in the fluconazole group and 45% in the amphotericin B group; there was still proof of fungal septicemia at the time of death in 1 patient given amphotericin B and 2 given fluconazole. CONCLUSION: Fluconazole showed fewer side effects than amphotericin B and was more convenient to use.

Family support and other social factors precipitating suicidal ideation.

To examine the effects of family support and demographics on suicidal behavior, 385 subjects completed a demographic questionnaire and a Suicidal Ideation Questionnaire (SIQ). Sixteen percent described themselves as "serious" ideators, while 59% were seen as ideators, numbers consistent with past suicide research. Multiple regression analyses revealed that the type of caregiver a person reported having while growing up accounted for a significant amount of the variance on ideator status. Serious ideators were more common among single parent households. Although many demographic variables were assessed, only the primary caregiver a person had as a child impacted their status as a suicidal ideator. This suggests that suicidal behaviors may occur due to a complex interaction between social factors and childhood care. The influence of living in a single-parent home may contribute to whether or not a person considers suicide.

Paraffin ingestion--the problem.

Paraffin ingestion is the commonest cause of accidental childhood poisoning in South Africa. Children from the lower socio-economic group are affected most. They drink paraffin in the summer months from bottles or intermediate containers, mistaking it for water or cold-drink. The children are predominantly male with a mean age of 24 months. The clinical picture is one of respiratory distress with a hospital case fatality rate of 0.74%. The use of paraffin as a source of household energy in South Africa is on the increase. Based on a modernisation index it would seem that this trend will continue into the next century. It can therefore be expected that the number of cases of paraffin ingestion will steadily increase if no active steps are taken to address the problem. Prevention should entail a wide spectrum of measures, the basis of which should be a child-resistant container. An effective durable, low-cost child-resistant container which is easy to pour from should be made available by petroleum companies and/or entrepreneurs and distributed through their network. This should be combined with health education on the danger of paraffin. Health care workers and administrators should be made more aware of the problem and become involved in health education and prevention. Further research should be undertaken on the effect a change in the colour of paraffin and the use of child-resistant caps would have on the incidence of paraffin ingestion in South Africa.