Predicting combined sewer overflows chamber depth using artificial neural networks with rainfall radar data.

Combined sewer overflows (CSOs) represent a common feature in combined urban drainage systems and are used to discharge excess water to the environment during heavy storms. To better understand the performance of CSOs, the UK water industry has installed a large number of monitoring systems that provide data for these assets. This paper presents research into the prediction of the hydraulic performance of CSOs using artificial neural networks (ANN) as an alternative to hydraulic models. Previous work has explored using an ANN model for the prediction of chamber depth using time series for depth and rain gauge data. Rainfall intensity data that can be provided by rainfall radar devices can be used to improve on this approach. Results are presented using real data from a CSO for a catchment in the North of England, UK. An ANN model trained with the pseudo-inverse rule was shown to be capable of predicting CSO depth with less than 5% error for predictions more than 1 hour ahead for unseen data. Such predictive approaches are important to the future management of combined sewer systems.

Laboratory studies investigating the processes leading to discolouration in water distribution networks.

Results are reported from laboratory experiments conducted to investigate the processes of discolouration within a water distribution system and specifically the concepts underpinning an empirical model proposed by Boxall et al. [Boxall, J.B., Saul, A.J., Skipworth, P.J., 2001. A novel approach to modelling sediment movement in distribution mains based on particle characteristics. Water Software Systems 1, 263-273.] and field validated by Boxall and Saul [Boxall, J.B., Saul, A.J., 2005. Modelling discolouration in potable water distribution systems. Journal of Environmental Engineering ASCE 131(5).]. The model is based on the hypothesis that discolouration is caused by the erosion and transport of fine particles, typically dominated by iron and manganese in the UK, that are attached to the pipe walls of the system by forces in addition to self-weight. These particles display cohesive-like properties and build up in layers on the pipe wall, conditioned by the usual daily flow patterns within the system. Discolouration events are caused by erosion of these layers due to changes in the system hydraulics and specifically changes in shear stress at the pipe wall, for example due to change in demand, a burst or the opening of a fire hydrant. Once cleaned from the pipe walls the layers re-accumulate under the usual conditions within the system. Experiments to determine cohesive layer behaviour and strength characteristics involved development periods followed by the measurement of the resultant discolouration when accumulated material was eroded by an increase in pipe-wall shear stress. The results support the empirical model concepts and hence its application. The results also suggest that the generation of material layers is influenced by the range of daily flow patterns, with greater variability reducing material accumulation, but not by the magnitude of steady state hydraulic conditions.

Rapid sonic characterisation of sewer change and obstructions.

This paper reports on the development of a low-cost, rapidly deployable sensor for surveying live sewers for blockages and structural failures. The anticipated cost is an order of magnitude lower than current techniques. The technology is based on acoustic normal model decomposition, The instrument emits short coded acoustic signals which are reflected from any sewer wall defect. The acoustic signals can be short Gaussian pulses or longer sinusoidal sweeps and pseudo-random noise. The processing algorithms used on the reflected signal can predict the extent and geometry of the pipe deformation, and the locations and approximate size of common blockages. The effect of the water level on the frequency of the fundamental mode has also been investigated. It is shown that the technique can be adapted to work reliably in relatively large 600 mm diameter sewer pipes.

Flooding in the future--predicting climate change, risks and responses in urban areas.

Engineering infrastructure is provided at high cost and is expected to have a useful operational life of decades. However, it is clear that the future is uncertain. Traditional approaches to designing and operating urban storm drainage assets have relied on past performance of natural systems and the ability to extrapolate this performance, together with that of the assets across the usable lifetime. Whether or not climate change is going to significantly alter future weather patterns in Europe, it is clear that it is now incumbent on designers and operators of storm drainage systems to prepare for greater uncertainty in the effectiveness of storm drainage systems. A recent U.K. Government study considered the potential effects of climate and socio-economic change in the U.K. in terms of four future scenarios and what the implications are for the performance of existing storm drainage facilities. In this paper the modelling that was undertaken to try to quantify the changes in risk, together with the effectiveness of responses in managing that risk, are described. It shows that flood risks may increase by a factor of almost 30 times and that traditional engineering measures alone are unlikely to be able to provide protection.

Baseline hydraulic performance of the Heathrow constructed wetlands subsurface flow system.

A constructed wetland treatment system has been commissioned by BAA (formerly the British Airports Authority) in order to attenuate airfield runoff contaminated with de-icant and other potentially polluting materials from Heathrow Airport. Airfield runoff containing de-icants has the potential to impose significant oxygen demands on water bodies. The site consists of a number of integrated treatment systems, including a 1 ha rafted reed bed canal system and a 2 ha sub-surface flow gravel reed bed. This research project is concerned with the performance of the subsurface flow reed beds, though attention will be paid in this paper to the operation of the whole system. Prior to the planting of the subsurface flow reed beds, flow-tracing experiments were carried out on the three different types of subsurface flow beds, so that the baseline performance of the system could be quantified. In association, data regarding the soil organic matter content was also collected prior to the planting of the beds. As expected, soil organic matter content is observed to be negligible within the bed, though a small amount of build up was observed in localised areas on the surface of the beds. This was attributed to the growth of algae in depressions where standing water persisted during the construction phase. Few studies exist which provide detailed measurements into the cause and effect of variations in hydraulic conductivity within an operational reed bed system. The data presented here form the baseline results for an ongoing study into the investigation of the change in hydraulic conductivity of an operational reed bed system.

The utilisation of engineered invert traps in the management of near bed solids in sewer networks.

Large existing sewers are considerable assets which wastewater utilities will require to operate for the foreseeable future to maintain health and the quality of life in cities. Despite their existence for more than a century there is surprisingly little guidance available to manage these systems to minimise problems associated with in-sewer solids. A joint study has been undertaken in the UK, to refine and utilise new knowledge gained from field data, laboratory results and Computational Fluid Dynamics (CFD) simulations to devise cost beneficial engineering tools for the application of small invert traps to localise the deposition of sediments in sewers at accessible points for collection. New guidance has been produced for trap siting and this has been linked to a risk-cost-effectiveness assessment procedure to enable system operators to approach in-sewer sediment management pro-actively rather than reactively as currently happens.

The use of hydrodynamic vortex separators and screening systems to improve water quality.

The paper reviews the evolution of Hydrodynamic Vortex Separators (HDVS) in the context of application as high rate rotary flow separators for achieving water quality improvements to meet with regulatory requirements in Europe and North America. The types of HDVS and their application for the control of wet-weather discharges such as combined sewer overflows (CSOs), sanitary sewer overflows (SSOs) and stormwater are outlined and a number of myths surrounding their use, dispelled. Reference is made to outputs of peer reviewed comprehensive monitoring, evaluation and demonstration projects on pilot and full-scale installations to demonstrate the efficacy and extensive track record of these systems. Recent developments and innovations in HDVS technologies are discussed, focusing on their combined use as solids liquid separators, contact vessels for wastewater disinfection, the incorporation of self-cleansing screening devices for the control of aesthetic pollutants (e.g. floatables) and the use of computational modelling for optimisation.

Fine sediment retention in storage chambers: an assessment of time-dependent effects.

The optimisation of the design of a storage chamber is generally based upon some measure of the chamber's sedimentation efficiency. In the UK, chambers that minimise the deposition of fine sediments are preferred. Previous laboratory and CFD-based studies to measure efficiency have focused on steady flow conditions. However, both the flow hydraulics within a storage chamber and the pollutant loading in the incoming sewage vary markedly during storm events. This paper outlines a CFD-based approach for determining "overall" chamber efficiency. The approach employs an unsteady volume-of-fluid multiphase model and stochastic particle tracking. Preliminary results from a simplified two-dimensional model are presented.

The effect of extended in-sewer storage on wastewater treatment plant performance.

A project funded by UKWIR is under way in the UK to develop a relatively simple methodology whereby the effects of the introduction of extended in-sewer storage at CSOs on downstream sewerage and treatment can be assessed. Recent legislation (UK and European) has compelled many sewer system operators to introduce systems which increase in-sewer retention times, and also retain more flow and load within sewer networks. The project has reviewed existing knowledge about the interaction between in-sewer flow and treatment plants, together with available models. The study is utilising a "benchmark" of 3 configurations of treatment plant and dynamic simulation using the WRc STOAT software, with minor modifications to ensure that effects on odour generation and nutrient removal processes are adequately modelled. As no existing sewer flow quality model can represent the range of conditions possible in sewer networks, a combined application of the Hydroworks model and a new model developed at Aalborg University is being used for this part of the study.

Ex post and ex ante willingness to pay (WTP) for the ICT Malaria Pf/Pv test kit in Myanmar.

Willingness to pay (WTP) for the ICT Malaria Pf/Pv test kit was assessed by the contingent valuation method using a bidding game approach in two villages in Myanmar. Kankone (KK) village has a rural health center (RHC) and Yae-Aye-Sann (YAS) is serviced by community health worker (CHW). The objectives were to assess WTP for the ICT Malaria Pf/Pv test kit and to determine factors affecting the WTP. In both villages WTP was assessed in two different conditions, ex post and ex ante. The ex post WTP was assessed at an RHC in the KK village and at the residence of a CHW in the YAS village on patients immediately following diagnosis of malaria. The ex ante WTP was assessed by household interviews in both villages on people with a prior history of malaria. Ordinary least squares (OLS) multiple regression analysis was used to analyze factors affecting WTP. The WTP was higher in ex post conditions than ex ante in both villages. WTP was significantly positively associated with the average monthly income of the respondents and severity of illness in both ex post and ex ante conditions (p < 0.001). Distance between the residence of the respondents and the health center was significantly positively associated (p < 0.05) in the ex ante condition in a household survey of YAS village. Traveling time to RHC had a negative relationship with WTP (p < 0.05) in the ex post condition in the RHC survey in KK village.

Opsonic human antibodies from an endemic population specific for a conserved epitope on the M protein of group A streptococci.

This study demonstrates the presence of epitope-specific opsonic human antibodies in a population living in an area endemic for group A streptococci (GAS) infection. Antibodies recognizing a conserved C-terminal region epitope (p145, sequence in single letter amino acids: LRRDLDASREAKKQVEKALE) of the M protein of GAS were isolated from human patients by affinity chromatography and were shown to be of the immunoglobulin G1 (IgG1) and IgG3 subclasses. These antibodies could reduce the number of colonies of serotype 5 GAS in an in vitro opsonization assay by 71-92%, compared with an equal amount of IgG from control adult donors living in non-endemic areas and without antibodies to p145. Addition of the peptide, p145, completely inhibited this opsonization. Indirect immunofluorescence showed that p145-specific antibodies were capable of binding to the surface of M5 GAS whereas control IgG did not. Using chimeric peptides, which contain overlapping segments of p145, each 12 amino acids in length, inserted into a known helical peptide derived from the DNA binding protein of yeast, GCN4, we have been able to further define two minimal regions within p145, referred to as pJ2 and pJ7. These peptides, pJ2 and pJ7, were able to inhibit opsonization by p145 specific antibodies. Finally, we have observed an association between the age-related development of immunity to GAS and the acquisition of antibodies to the conserved epitope, p145, raising the possibility of using this epitope as a target in a prophylactic vaccine administered during early childhood.

Effect of context and adjuvant on the immunogenicity of recombinant proteins and peptide conjugates derived from the polymorphic malarial surface antigen MSA2.

We have identified a 51 kDa glycosylated myristylated merozoite surface antigen (MSA2) as the target of a number of monoclonal antibodies which inhibit in vitro invasion of the human malarial parasite Plasmodium falciparum. This antigen has been shown to exist in a limited number of strain specific forms but despite wide variation in the sequences of the internal repeat regions both N and C terminal elements of the protein are almost totally conserved. Accordingly, we prepared a large number of overlapping peptide constructs and demonstrated that one peptide SNTFINNA (E71) from the N terminus and two peptides, QHGHMHGS (G5) and NTSDSQKE (G12) from the C terminus could, when suitably conjoined to the carrier protein diphtheria toxoid (DT), elicit antibodies reactive with MSA2 from diverse strains of P. falciparum. Here we compare the immunogenicity of these peptide constructs with two recombinant proteins containing the entire amino acid sequence of MSA2 from the FCQ-27/PNG strain (1609) and the 3D7 strain (1623). We have formulated these recombinant and peptide antigens with Freund's adjuvant, Alum and Algammulin. Both recombinant and peptide antigens elicit high titre antibodies when tested by ELISA against the immunogens themselves. Although both recombinant proteins include the constant region peptide sequences E71, G5 and G12, the extent of ELISA cross reaction between antibody raised against recombinant and peptide antigen or antibody raised against peptide and recombinant antigen is small and sporadic, and depends to an extent on the adjuvant employed. Antisera against both recombinant proteins 1609 and 1623 detected either recombinant on Western blots, as well as detecting native MSA2 in whole protein extracts from both FCQ-27/PNG and 3D7 strains. Antisera against peptide construct E71 recognized recombinant 1609 but not 1623 but recognized the native MSA2 in both strains studied. Antisera against peptide construct G5 showed a similar pattern of recognition but also detected recombinant 1623 on Western blotting. These results emphasize the importance of context and adjuvant on the ability of selected immunogenic epitopes to elicit antibodies appropriately directed against the native antigen.

Plasmodium falciparum: highly mobile small vesicles in the malaria-infected red blood cell cytoplasm.

A dynamic population of small vesicles within the cytoplasm of live malaria-infected red blood cells has been studied using a laser scanning confocal microscope. Acridine orange was used to follow the movement of vesicles within the infected red blood cell cytoplasm, including the budding of vesicles from the malarial parasite. These highly mobile vesicles are found predominantly in mid- to late ring-stage parasites and are almost entirely absent from young rings and mature trophozoites. Since the known parasite modifications of the red blood cell plasma membrane in mid-ring-to early trophozoite-stage parasites correlates with the appearance of acridine orange-staining vesicles, these vesicles may be an important component in the transport of parasite proteins across the infected red blood cell cytoplasm.

Vaccine strategies for malaria: applicability in areas of seasonal or epidemic malaria.

The likely effects of different vaccine strategies was tested using computer simulation of malaria transmission. In areas of seasonal or epidemic malaria, vaccines directed against all stages (pre-erythrocytic, erythrocytic and sexual) gave similar reductions in disease transmission. These models indicate that such vaccines may be much more effective that commonly predicted. The major effect will be to slow the spread of, rather than totally prevent malaria. As such, the use of such vaccines will be heavily dependent on integrated control programs involving other forms of control.

Mapping of the region predominantly recognized by antibodies to the Plasmodium falciparum merozoite surface antigen MSA 1.

The locations of the epitopes of a panel of mouse monoclonal antibodies directed against the Plasmodium falciparum merozoite surface antigen MSA 1 were mapped by using naturally occurring processed fragments, by chemical cleavage of the protein and by comparison of the isolate-specificity of binding with known sequence variation. By these criteria, the most antigenic region occurs in the cysteine-rich, invariant 19-kDa carboxyl terminal domain with 12/19 monoclonal antibodies (mAbs) binding to this region. One of these mAbs recognized an epitope near the C-terminal putative glycosylphosphatidylinositol anchor site. This was the only mAb which significantly inhibited parasite growth in vitro. The other mAbs recognized conformational epitopes involving the cysteine residues located throughout this fragment. This study has identified further naturally occurring processing sites and a consensus processing site sequence is now emerging.

Geographically restricted heterogeneity of the Plasmodium falciparum circumsporozoite protein: relevance for vaccine development.

The design of a subunit vaccine against the malaria parasite relies on the epitopes recognized by T cells being identified and polymorphisms therein being defined. Here we present the analysis of a 354-bp fragment of the circumsporozoite (CS) protein encompassing defined proliferative and cytotoxic T-cell recognition regions. We reveal that the polymorphism of CS protein T-cell sites appears to be very limited among Plasmodium falciparum isolates prevalent in certain geographical regions, in particular Papua New Guinea. Furthermore, the more extensive polymorphism noted in other areas appears to be restricted. Although the extent of variation observed for the T-cell recognition domains suggests that any vaccine designed to stimulate this form of immunity will need to be polyvalent, this variation appears to be finite and the combination of peptides necessary for inclusion in a polyvalent vaccine may be small. If ways to increase immune responsiveness can be found, then a vaccine designed to stimulate CS protein-specific T-cell activity may prevent malaria.

Comparative study of the T cell response to two allelic forms of a malarial vaccine candidate protein.

T cell responses to two allelic forms of the merozoite surface Ag 2 (MSA2) of Plasmodium falciparum were mapped in mice using the rMSA2 proteins, Ag 1609 which has the sequence of the FCQ27/PNG strain and Ag 1615 which has the sequence of the Indochina 1 strain. Lymph node cells of BL/10 and B10.BR mice immunized with either Ag 1609 or Ag 1615 responded to both Ag in in vitro proliferation assays. Lymph node cells of BALB/c mice did not respond. The T cell determinants recognized by the responder strains were mapped to conserved and variant regions of these Ag using overlapping synthetic peptides. The determinants recognized by each mouse strain were distinct. Marked difference in sequence between the central regions of the two rMSA2 proteins did not affect antigenic processing of the conserved N and C terminal regions. Hence lymph node cells of BL/10 mice immunized with either Ag 1615 or Ag 1609 recognized an immunodominant T cell determinant at the highly conserved N terminal end within the sequence YSNTFINNAYNMSIR (peptide 3b) and B10.BR mice similarly immunized recognized an immunodominant determinant at the highly conserved C terminal within the sequence CTDGNKENCGAATSL (peptide 23). Several peptides identified as containing immunodominant T cell determinants specific to BL/10 mice induced peptide-specific T cells in both BL/10 and B10.BR mouse strains when used as immunogens. However, the ability of the peptide-primed T cells to proliferate in response to the rMSA2 proteins was confined to BL/10 mice. An example of this was observed with peptides 3b and N (KNESKYSNTFINNAYNMSIRRSMAN). Peptide N was able to prime B10.BR and BL/10 mice for an enhanced antibody response when these mice were subsequently immunized with Ag 1615 even though Ag 1615-specific T cell proliferation was not detected in B10.BR mice primed with N. The study concluded that 1) conserved sequences such as peptide N when used in vaccines may give rise to MSA2-specific memory Th cells amenable to boosting by subsequent exposure to all parasite strains and 2) peptide priming may be a useful pathway for inducing defined memory Th cells in a wider population and for preferentially inducing T dependent over T independent responses to some malarial Ag.

Immunological fine structure of the variable and constant regions of a polymorphic malarial surface antigen from Plasmodium falciparum.

The 51-kDa merozoite surface antigen MSA2 of Plasmodium falciparum shows considerable strain-dependent polymorphism. Although marked sequence variation occurs in the central region of the molecule, the N and C-terminal sequences are highly conserved. A number of monoclonal antibodies directed against MSA2 have been described which inhibit parasite growth in vitro, but these are all directed against variable regions. In an attempt to raise strain independent antibodies we have prepared peptide-diphtheria toxoid (DT) constructs from 36 N-terminal octapeptides spanning the constant region and extending into the variable region of the FCQ/27 PNG variant staggered by one amino acid at either end. Similarly, we prepared 26 C-terminal octapeptides spanning the C-terminal constant region as well as 10 octapeptides from the variable region of the Indochina I variant MSA2. Most of the peptides elicited antipeptide titres in excess of 1/10(4) when administered to mice as peptide-DT adducts emulsified with Freund's complete adjuvant. Only 3 of the 43 N- and C-terminal constant region peptides elicited antibodies which reacted appropriately on immunofluorescence (IFA) or immunoblotting analysis with the intact MSA2 of both strains studied (FCQ/27 and Indochina I), whereas 3 other peptides from the variable region elicited antibodies reactive with the parent MSA2 only. Peptide constructs eliciting antibodies recognising the intact protein corresponded to elements in the cognate sequence of high antigenicity as predicted by the Jameson and Wolf algorithm.

High-titer antisera production using three adjuvants and peptide conjugates derived from malarial surface antigen MSA-2.

We have identified a 51-kDa glycosylated myristoylated merozoite surface antigen as the target of a number of monoclonal antibodies that inhibit P. falciparum invasion. This antigen has been shown to exist in a limited number of strain-specific forms, but despite wide variation in the sequences of the internal repeat regions both N- and C-terminal elements of the protein are almost totally conserved. Accordingly, we prepared a large number of overlapping peptide constructs and demonstrated that one peptide, SNTFINNA (E-71), from the N-terminus and two peptides, QHG HMHGS (G-5) and NTSDSQKE (G-12), from the C-terminus were capable, when suitably conjoined to carrier protein diphtheria toxoid, of eliciting antibodies reactive with MSA-2 from diverse strains of P. falciparum. Here we compared the immunogenicity of the peptide constructs when formulated with a Freund's adjuvant, alum and algammulin. Both peptide constructs E-71 and G-5 elicit high-titer antibodies with all three adjuvants when tested by ELISA against the immunogens themselves and by Western blotting of whole parasite extracts from two distinct parasite strains.

Structural diversity in the 45-kilodalton merozoite surface antigen of Plasmodium falciparum.

An integral membrane protein associated with the merozoite surface of Plasmodium falciparum termed merozoite surface antigen 2 (the 45-kDa merozoite surface antigen), occurs in antigenically diverse forms. Here we report the sequences of the MSA 2 gene from two other isolates of P. falciparum. The 43 N-terminal residues and the 74 C-terminal residues of all three MSA 2 sequences are highly conserved, but between these conserved regions there are dramatic differences among the alleles. Instead of the two copies of a 32-amino-acid repeat present in the MSA 2 of isolate FC27, MSA 2 from clone 3D7 and isolate Indochina 1 contain 5 and 12 copies respectively of the four amino acid sequence Gly Gly Ser Ala. The sequences flanking the repeats also differ among the three antigens. The repeats in MSA 2 appear to be immunodominant during natural infection, and antibodies to the repeat regions of different alleles react with a restricted number of parasite isolates.