The past 10 years have witnessed a trend toward improved services both in water supply and sanitation by optimising the use of control systems. To make sure water will be available and affordable in the future we require innovation. This is reinforced by the following factors:
* Energy consumption and costs are becoming an increasingly important consideration.
* Variations in local demographic conditions are leading to significant increases or decreases in water consumption.
* Increasing attention is being focused on monitoring and reducing water losses, with the objective of achieving sustainable operations.
* Effluent quality is receiving more attention as requirements become more stringent.
* Water reuse is becoming a necessity in some parts of the world, because of the scarcity of clean water.
* Energy (cost) and the carbon footprint are becoming increasingly important considerations.
* Control is rapidly improving and becoming more cost effective, allowing for fully automated plant operation.
According to Royal HaskoningDHV, up to 40% of the total energy footprint of a city can be determined by the water related services. In fact, electricity costs can represent up to 40% of total operating costs within the water industry. And that will increase significantly with escalating energy prices in South Africa. It is time to make a plan.
Royal HaskoningDHV has developed a range of innovative products for the water and waste water industries. This Aquasuite product family provides intelligent solutions for advanced monitoring and control of water supply and sanitation systems. In numerous countries all over the world more than 60 Aquasuite systems have been installed in water reticulation systems and water treatment plants. Because of the significant savings in energy and operational costs, return on investment can be reached in periods from a couple of months to a couple of years.
From 2014, these tried and tested products are available to South African and African water service providers. The product suite consists of solutions to optimise energy consumption throughout the water value chain using state-of-the-art prediction algorithms, web dash boards for management information and detailed user-friendly reporting.
OPIR – Optimal control of water supply systems
OPIR is an advanced control software product that optimises the operation of water production and transport facilities, prevents turbidity peaks in the clean water and reduces energy consumption in water supply systems. It is the result of decades of experience with control systems in numerous water supply applications and is based on in-depth knowledge of production and distribution processes. OPIR contains an adaptive demand prediction control, which automatically identifies the specific consumption patterns of an area and uses these to predict the water demand for the next 48 hours. On the basis of the available storage capacity, OPIR determines set points for the water production and distribution, resulting in a more constant flow compared to conventional pump control systems. Additional functionalities include:
* Pressure control: calculates an optimal pressure set point for the distribution pumps at which all pressure conditions are satisfied.
* Performance Dashboard: allows for ongoing evaluation of daily, weekly and current performance, and permits quick identification of any abnormalities.
* Energy monitor: monitors the effect of OPIR performance on energy consumption.
* Abstraction permits monitor: predicts abstraction amount up to a year.
OPIR can optimise the operation of any water supply system: urban or rural, large or small, basic or complicated and with or without scada. It provides solutions tailored to consumer needs and offering the following benefits:
* 5-10% reduction energy costs.
* 5-10% reduction of water loss.
* 60-80% reduction in flow variation.
* 10-20% reduction in turbidity.
* Automatic control.
* Predictable and easy operation.
CarCON – Optimal control for wastewater treatment plants
CarCON is an advanced control software product that optimises nutrient removal and minimises energy and chemical consumption in a wastewater treatment plant. It is the product of decades of experience with control systems at numerous treatment plants and in-depth knowledge of treatment processes. The system can optimise each process-related control loop in the treatment, for example: aeration, return activated sludge, internal recirculation, chemical dosing for phosphorous removal and carbon-source dosing.
CarCON predicts the influent flow for the forthcoming 48 hours. To do so, this forecasting module requires no historical data and is adaptive, that is, self-learning. At a municipal WWTP, the influent flow shows a typical diurnal pattern, which depends on the size of the surrounding area, the sewer system (distances) and the industrial contribution. The diurnal pattern may also show a weekly or seasonal variation, depending on local customs and industrial contributions. The prediction takes different types of days into account and deals with holidays separately. Any data it captures that deviate excessively from the prediction are not ‘considered’ by the module.
The influent prediction significantly boosts control performance for several reasons:
* Most energy is saved in aeration: savings of up to 25% can be achieved compared to traditional oxygen controllers. Even compared to various modern ammonium-based control schemes, measurements indicate that CarCON offers up to 5% in energy savings.
* Another big energy consuming element is RAS pumping. Depending on the RAS system’s design, CarCON can bring about energy savings of up to 40% in this area.
* Significant improvement in removal efficiency of N and P: up to 50% N-removal improvement.
* Prediction-based control means smooth control: little variation, little equipment switching (less wear) and better overall process conditions.
* Prediction-based control means accurate control: operational set points can be chosen that are less conservative and closer to discharge requirements.
Flexibility is one of CarCON’s outstanding qualities and several control configurations are possible. These options include:
* Aeration: CarCON predicts the required oxygenation capacity and adjusts the set point according to the measurements taken, such as ammonia, nitrate, oxygen and phosphate.
* Phosphate: for wastewater treatment plants that apply biological phosphorous removal, the system continuously determines which removal process (NH4/PO4), directs the aeration and monitors dosing levels.
* Internal recirculation: influent flow prediction is used to determine the internal recirculation flows. Flow set points are adjusted according to the nitrate measurement, and if necessary constrained, depending on the ORP and/or second nitrate measurements.
* Return activated sludge: influent flow prediction is used to determine the optimal RAS flow, calculated through a mass-balance using MLSS measurements and the SVI. CarCON also has a smart, energy-saving start-stop control for low loading conditions.
* Chemical dosing for phosphorous removal: predicts the required dosing capacity and adjusts it according to the measurements taken.
CarCON is highly reliable thanks to its predictive nature and contains several fall back algorithms in the event that sensors malfunction. Even in the absence of any functioning online measurements, the prediction still provides intelligent control for at least 48 hours. Moreover, laboratory data can be entered into CarCON in order to control the plant when online measurements are not available. In the event that the CarCON system or communication itself fails, process control is still guaranteed since the back-up plant control in the PLC (or DCS) is automatically activated.
Management Information System (MIS) and dashboards
The Aquasuite software solution provides management with key information through industry standard dashboards that allow assessments of plant performance.
More detailed information is available via the AquaVision MIS System that provides fully detailed, user-configurable reports for multiple plants. This could really improve the Blue and Green Drop status of the several water service authorities in South Africa.
The Aquasuite family of products provide innovative solutions for water and wastewater industries in South Africa. The effects of the current electricity crisis can be mitigated by using this software and it will also assist in addressing the potential water crisis that the country faces.
For more information contact Hillary Erasmus, Royal HaskoningDHV, +27 (0)11 798 6511, [email protected], www.rhdhv.co.za
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