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Project title and report nr

Description

Quantification the influence of air on the capacity of large diameter water pipelines and developing provisional guidelines for effective de-aeration

The results are discussed in the following reports:

Volume 1: WRC Report no. 1177/01/03

Volume 2: WRC Report no. 1177/02/03

The contents of Volume 1 comprises:
•Introduction
•Influence of air on pipelines
•Field investigations
•Experimental work
•Numerical modeling of air release from pipelines (CFD)
•Effective de-aeration of pipelines
•Further developments

Volume 2, includes the following sections:
•Introduction
•Intrusion of air into pipelines
•The consequences of air in pipelines
•Hydraulic transport of air
•Air valves
•Implementation of a new pipeline
•Sizing and positioning of air valves
•Typical installation details of air valves
•User comments

Review of factors that influence the energy loss in pipelines and the procedures to evaluate the hydraulic performance for different internal conditions

WRC Report no. 1269/01/06

The geographically mismatch of the water demand centres and the water resources necessitate the transport of water over long distances and high elevation differences. On average water is transported about 350 km in South Africa (Basson, Van Niekerk & Van Rooyen, 1997). High energy costs and the increasing demand require that the water transfer infrastructure should function optimally. Since the 1930’s various researchers contributed to the identification and development of factors and relationships to quantify the energy loss in pipelines, which led by 1958 to the development of pressures, head losses and discharge relationships (Chadwick and Morfett, 1999) for the design and evaluation of pipes and pipe systems.

There are various factors that influence the hydraulic capacity and pipeline designers need to take all of these into consideration during the design. For instance the estimation of roughness parameter for a pipeline has a significant effect on the hydraulic capacity and operational costs. An underestimation of this parameter can be catastrophic when the required demand cannot be met. The better quantification and identification of these factors required investigation, reviewing the available literature, conducting experimental investigations, perform field investigations and develop software that will assist designers in evaluating a pipeline system over its full life cycle.
The aims of the study were:
•The quantification of the factors influencing the friction loss in pipelines.
•Establish the relationship between water quality, operating conditions and the hydraulic performance of different liner systems and pipe materials.
•Development of selection criteria for liner systems and pipe material.
•Quantify the economic influence of increasing friction losses in a pipe system.
•Development of a computer model to evaluate whether to replace, refurbish or extend existing infrastructure components.
•Establish the effectiveness of different pipe rehabilitation options on the friction loss characteristics and liner integrity.

The potential application of Genetic Algorithms in the water industry

WRC Report no. 1144/01/01

The past decade marks the development of computational capacity that far exceeds the capacity of the “instructor” to define options to be evaluated when optimisation has to be achieved.

The Government’s objective to provide “water for all” made it essential that the limited capital has to be employed to provide the maximum benefit. The optimal decision in terms of expansion, addition or rehabilitation of water supply systems has to review the conflicting demands and select a cost effective and efficient solution.

Within the context of water supply, there are numerous variables that can influence the selection and hence the final cost of system improvements.
These variables include:
•The high variance in rainfall and runoff,
•the availability of alternative water supply,
•the demand pattern variability,
•the operational ability of the system,
•the maintenance requirements,
•the running cost-especially power cost and
•the affordability and willingness to pay for services.

The determination of the optimal selection of system components requires techniques that can be employed to assist the decision-maker in finding the appropriate solution within the environment of all the possible solutions (Solution space).
 

The aim of this study was to evaluate the application of genetic algorithms in the optimisation of different components of water supply projects, viz:
•pump selection and scheduling
•optimal pipeline diameter selection
•valves and surge alleviating devices selection
•management of water supply projects
•alterations and extensions required in the upgrading of the capacity of water supply infrastructure.

Application and conceptual development of genetic algorithms for optimization in the water industry

WRC Report no. 1388/01/05

This study evaluated the application of genetic algorithms in the optimisation of different components of water supply projects and conceptually developed the procedures for the implementation thereof.

Based on the available literature study, as well as the feedback from water supply authorities, the need for the application of GAs as an optimisation technique in the water industry was defined. The potential applications of GAs in the water industry in South Africa are:
- Hydrology and water resources assessment,
- Network optimisation,
- Optimisation of rehabilitation, extension and upgrading of distribution networks during the planning and design phase,
- Operation and maintenance scheduling

This study objective was to provide the conceptual development of procedures to implement GAs as an optimisation technique for water resources assessment and network optimisation.

A high level scoping investigation into the potential of energy saving and production/generation in the supply

WRC Report no. KV238/10

With regard to energy saving and production a number of energy efficient products have been introduced varying from energy efficient globes, fuel efficient cars and high production breeds of modified plant material, as well alternate renewable energy sources. For example, solar energy has also been developed as a local alternative source but However, except for large scale hydro-power and recently micro-scale hydropower, very little has been done to determine other alternative mechanisms of energy production from the supply of water and the efficient use of energy. For example, high pressure piped conduits have the potential to provide very low-cost energy/power in small quantities. Until now these options were not fully exploited and researched, therefore making it imperative to undertake this scoping exercise. South Africa is blessed with substantial transfer of water through piped conduits and this offers significant potential for exploitation, especially to the benefit of remote rural settlements requiring small quantities of energy. The focus thus is to establish the potential of how the unused pressure energy in the water distribution systems could be utilized as a potential power source by the end users by using micro-hydropower generating facilities.

Waterborne Sanitation Design Guide

WRC Report no. TT 481/11

This report summarizes the available knowledge, information and advancements of all waterborne sanitation systems used in South Africa. The objective of the report is to provide a concise guide for the analysis and design of waterborne sanitation systems.

The four main waterborne sanitation systems which are described in this guide are:

• Conventional gravity sewer
• Vacuum sewer systems
• Small-bore sewer
• Simplified sewerage

A summary description with advantages and disadvantages of these systems is provided. A technical design criterion for designing each of these systems is given with a worked example guiding the designer through the process to be followed.

Waterborne Sanitation Operation and Maintenance Guide

WRC Report no. TT 482/11

The function of a waterborne sanitation system is to collect and convey wastewater in a hygienic manner. Operation and maintenance of this sewer system means making sure that all its components are kept in good operating condition. Planners, designers, the construction team and the administrators have a joint duty in providing an efficient system. The operator can then, based on the available resources provided, operate and maintain the system.

Municipal sanitary sewage collection and conveyance systems are an extensive, valuable and complex part of the country’s infrastructure. The waterborne sanitation system consists of pipelines, conduits, pumping stations, pressure mains and other facilities used to collect the wastewater from residential, industrial or commercial sources and convey it to treatment facilities. The public expects these systems to function effectively at a reasonable cost.

Information has been synthesized from a wide variety of sources and tailored to South African conditions to produce a comprehensive guide on operation and maintenance of waterborne sanitation systems. Some sources of information were heavily relied upon in creating this guide. These include the document Alternative Sewer Systems (WEF Manual of Practice, 2008); the NEIWPCC (2003) manual entitled Optimizing Operation, Maintenance, and Rehabilitation of Sanitary Sewer Collection Systems; the Sanitary Sewer Overflow Solutions - Guidance Manual (ASCE, 2004); and the Sewer Design Manual (Bureau of Engineering, 2007).

This document comprises the following sections:

• Types of maintenance
• Equipment required for maintenance
• Maintenance requirements and frequency
• Operational requirements
• Safety measures and practices
• Inspection forms and checklists

Determination of the change in Hydraulic Capacity in Pipelines

WRC Report No 1820/1/12

During the design stage of any water transporting pipeline, it is essential to predict the anticipated future hydraulic behaviour of the system. This requires an understanding of the relative influences of water quality, pipe material aging and operational variation on the expected change in the hydraulic performance of the system. Future expected hydraulic performance can be predicted if the influence of these factors on the expected absolute roughness of pipelines can be quantified. This study aimed to obtain as much as possible operational field data of a number of pipelines in order to:
 

• Determine the current roughness and derive the roughness variation and roughness decay;
• Compare the calculated roughness obtained from the field tests with the available literature;
• Compile a database to be used as a guide in selecting the appropriate expected future roughness required in the design and optimisation of the water system components. In the design of new pipelines or the refurbishment, upgrade or replacement of existing components of the water supply system the cost of energy as well as the influence of biofilm growth in the pipeline should also be reviewed. These aspects were also included in this research project.

Influence of energy cost on the optimization of system components
The contribution of energy cost during the life cycle outweighs the capital cost of most pumping
systems, requiring thorough analyses of the optimal component design. A recent review (Van Wyk, 2010) of 11 pump stations in the Tshwane Metropolitan Council’s water distribution systems reflected that the electricity tariff structure as agreed upon by the Energy Regulator (NERSA) and Eskom requires larger diameters to provide an optimized pumping system in the majority of these cases for a number of possible energy cost scenarios which were identified.

Influence of biofilm growth on the hydraulic capacity of pipelines
The assessment of the hydraulic performance of the main supply pipeline in the Lower Blyde River Irrigation Systems reflected that the presence of the biofilm significantly reduced the hydraulic capacity of pipeline. Biofilm, which is present in all water carrying pipelines, will however not only reduce the hydraulic capacity of pipelines but could also lead to a loss of operational control due to the blockage of the communication pipes of the pilot control valves.

Roughness assessment of existing pipelines
A number of pipelines were hydraulically assessed in South Africa and Namibia. Based on the recorded field data, the roughness in the pipeline segments was calculated. Accurate pressure recordings and flow measurements are essential to be able to calculate the roughness in the pipeline.

Development of an information system (IS) for water infrastructure
An information system (IS) was developed with the objective to capture sufficient data on current systems to be used in future designs and to have the ability to conduct continuous assessments of pipelines in South Africa. The IS will allow designers and managers of pipelines to study the performance of different types of pipelines in varying areas under different operating conditions. The information is essential to improve the design of future pipeline systems and to optimize the maintenance on existing pipelines. The accurate prediction of expected future capacities will enhance the planning and management of the infrastructure ensuring a timeous implementation of augmentation schemes.

Influence of catchment development on peak urban runoff

WRC Report no. 1752/1/12

The research reviewed catchment response due to urban development on the basis of comparative assessment. This required the identification of similar rainfall in the catchment during different development stages for which gauged flow rates were recorded. The hypothesis which was reviewed here relates to the statement that urban development which creates more impervious areas on the one hand also generated longer times of concentration due to the changes in the length of the flow path as well as more temporal storage capacity which could result in a higher groundwater recharge.

The hypothesis that the influence of urban catchment development will decrease the peak runoff has neither been proved nor disproved

Grouted lining systems for the renovation of old steel pipelines and the design of new pipelines

WRC Report no. 1448/1/12

In South Africa steel pipes have been installed as late back as 1930. Steel pipes amongst other need to be protected against corrosion. This is normally achieved by the provision of an internal lining and external coating. Some of the liner systems that have been used in the past have to be replaced and in the case of Rand Water the largest water utility, consideration is given to install grouted viscous-elastic liners in a number of their pipelines to extend their useful life. Practical challenges exist to install liners at joints, bends, pipe transitions, fittings, branches and at valves. In selecting a liner, one of the major aspects to consider is whether the pipeline still has sufficient structural capacity for the intended use. The structural contribution of the different layers in the composite pipe influences the buckling characteristics of the pipeline. Thus the objective of this study was to investigate alternative lining systems applicable for South African conditions. The experimental work involved the following:

• Establish the ease of installation for liners which could be used for steel pipelines;
• Test the installation of joints;
• Establish how the liner performs under high internal pressure; and
• Determine if the liner could be installed along bends.

Through the experiments the study has demonstrated that HDPE liners do have potential in the rehabilitation of steel pipeline, since they also provide some structural strength and possible ease of installation, as well as overcome some of the problems associated with current lining practice. The study has shown that more work needs to be done on the use of the materials on pipe bends and other fittings.

Status Review and Requirements of Overhauling Flood Determination Methods in South Africa

WRC Report no. TT563/13

The procedures which were developed in South Africa for the estimation of design floods can be characterised as methods which related to the analysis of observed floods and those methods which asses the rainfall data and catchment response (Smithers and Schultz, 2003). The development of most flood calculation procedures currently used, occurred prior to 1990 (HRU, Hiemstra, Schultze) while later contributions attempt to provide a calibrated standardized procedure for flood calculations (Alexander, 2003), reviewed the relationship between peak discharge and volume of the runoff hydrograph (Görgens, 2007) and proposed a new statistical assessment of flood peak determination (Nortje, 2010).

Shortcomings of the current flood estimation procedures

This project highlighted the following shortcomings in the flood estimation procedures. A general shortcoming of the current procedures is that the hydrological data sets which were used were short and in most cases excluded the severe weather incidences of the 1980s and the recent floods. It is likely that in the case of rainfall-based methods, the relationships between catchment response and rainfall could change if longer data sets are used. The use of extended records might reflect:

• A different depth-duration frequency relationship for the determination of point rainfall;
• The procedure for the determination of the design storm rainfall might change if the record length is extended; and
• That for certain cases under consideration the antecedent moisture conditions in the catchment should be included.

Furthermore it is anticipated that the longer observed storm records might reflect:

• The number of catchments with similar hydrological response (be it for the RMF; SDF ; JPV or REFSSA procedure) might have to be redefined; and
• The statistical relationships to quantify flood peaks and flood volumes in terms of recurrence interval could be extended.

A number of proposed research priorities have been identified and some concerns noted.

Scoping study: Energy generation using low head technologies

WRC Report no. KV323/13

In the execution of this study attention was firstly given to identify the available low head hydropower technologies, followed by the identification of sites where the technologies can be implemented and finally the discussion of specific sites where the technology can be implemented.

Defining low head power generation
Low head hydropower generation refers to electricity generated from a relatively low pressure head normally found in rivers or irrigation canals, and is applicable to sites with less than 5 metres of head (Campbell, R.J., 2010). This definition is however negated by the definition reflecting that heads up to 30 m should be identified as low head (ESHA, 2004).

Turbine types
Turbines are broadly divided into two groups: impulse- and reaction type turbines. Impulse type turbines are more suited to high head applications where reaction type turbines are widely used for low head sites. Table i indicates the different technologies for different operating heads associated with the specific turbine group.

Information of the potential technologies was obtained and for each a data sheet was compiled.

The potential sites where low head hydropower can be installed in South Africa are grouped as follows:
 

• Dams and barrages (retrofitting);
• Rivers;
• Irrigation systems (canals and conduits); and
• Urban areas (industrial and urban discharge, storm water systems and WDS).

Infrastructure and the determination of the remaining operational life

WRC Report no. 1950/1/13

The management of the physical assets involves a wide scope and range of processes including acquisition, control, use and disposal of the assets in a manner that satisfies the constraints imposed by business performance, environment, ergonomics, and sustainability requirements. The focus of this research is on condition assessment of the water services infrastructure components and the development of guidelines for the condition assessment of these components. The objective was to focus on what should be done and therefore the research will not contain any detail of a prescribed protocol of how condition assessment for the different system components should be conducted. The methodology included the review of existing operational information to gain insight into the procedures followed to conduct asset management and to relate the operational experience to the remaining useful life by formulating a relationship between the status and remaining life. The outputs emanating from the study include:

1. Data requirements to define the water infrastructure components;
2. Conceptual model between performance and life expectancy;
3. Applicable non-destructive techniques for condition assessment of water transfer infrastructure;
4. Description of the economic evaluation techniques to compare replacement or refurbishment; and
5. Development of software (spread sheet) to determine the remaining useful economic life

Conduit Hydropower Pilot Plants

WRC Report No TT596/14

Conduit Hydropower Development Guide

WRC Report No TT597/14

An initial WRC scoping study highlighted the potential hydropower generation at the inlets to storage reservoirs. In South Africa there are 284 municipalities and several water supply utilities, mines, all owning and operating gravity water supply distribution systems which could be considered for small, mini, micro and pico scale hydropower installations.

Most of these water supply/distribution systems could be equipped with turbines or pumps as turbines, supplementing and reducing the requirements for pressure control valves. The hydro energy may be used onsite, supplied to the national electricity grid or feeding an isolated electricity demand cluster.

Worldwide, hydropower is the most established and reliable renewable energy technology. Traditionally, hydropower is used in large dams where the outlet flow is turbined to generate electricity.
Due to the exploitation of most large dams where this is economically viable, focus has shifted to the use of small scale, mini and micro hydropower as a way to generate electricity, primarily by retrofitting hydropower technology to existing water supply infrastructure.

The application to install hydro electric turbines in a water distribution system is fairly new in South Africa and thus three pilot plants, listed below, were constructed showcasing several of the intricacies in the development process and to demonstrate the technologies

• Pierre van Ryneveld (16 kW)
• Brandkop (96 kW)
• Newlands 2 (2 kW)

This research study indicated that it is feasible and technically possible to generate energy from distributions systems. The hydropower development guidelines assist in identifying locations, selecting the turbine and determining the feasibility thereof. To assist in the feasibility calculations, showing that it is a viable investment cost functions have been developed. The practical aspects are demonstrated with the three constructed, operational pilot plants installations.

“As long as people use water, renewable hydroelectricity can be generated”

Additional parameters for the design of straight ogee spillways

WRC Report No 2253/1/15

The Ogee spillway relationship (USBR, 1987; Vischer & Hager, 1999) is used to define the required profile of the spillway section of a dam or hydraulic structure. The Ogee relationship describes the bottom nappe associated with a sharp-crested weir. The current relationship accommodates the influence of the unit discharge, the angle of inclination of the upstream wall face, as well as the relationship of upstream pool depth to the total upstream energy at the apex of the structure. In cases where the discharge flow rate exceeds the design flow rate the nappe coheres to surface of the spillway and a sub-atmospheric pressure region is generated that could lead to cavitation (Savage & Johnson, 2001; Momber, 2000). Cavitation usually occurs during a unit discharge, in excess of the design head, when the surface pressure could reduce at positions along the spillway to sub-atmospheric pressure. This may cause the formation of vapour cavities. The vapour cavities (also referred to as miniscule air bubbles) will progress along the flow path due to the high flow velocity on the spillway to a region downstream where sufficient pressure is available leading to the collapse of the air vacuum. This generates localized high pressures. Should these vapour cavities collapse near the spillway structure, there will be some superficial damage to the spillway’s surface where the vapour bubble has collapsed. This cavitation damage can ultimately result in substantial erosion and, if ignored, will subsequently cause failures of the spillway chute. Minute cracks, offsets and increased surface roughness intensify this cavitation process. The extent of cavitation damage is a function of the cavitation indices at key locations on the spillway chute and the duration of flow over the spillway. This emphasizes the need for a geometric, accurate and precise spillway profile to reduce the possibility of sub-atmospheric pressure formation (U.S. Army Corps of Engineers, 2009). The current Ogee spillway relationship lacks to incorporate the asymmetrical cross sectional upstream geometry of the spillway, the relative orientation of the spillway with regard to the approaching flow and the curvature of the spillway in relation to the depth of the structure.

Patent title

Description

Picture

Rotoscope

Real time monitoring of Biofilm growth

Cavitation prevention in control valves

 Prevention of cavitation in control valves by means of air induction