RSSLoch Turret Water Treatment Works
High rate ballasted clarification process Actiflo and Multiflo Lamella Sludge thickening plant at Loch Turret Water Treatment Works
Project Outline
Loch Turret Water Treatment Works is the highest water works in Scotland at 1,178 feet above sea level and located 2.2 miles north of Crieff, home to the Glenturret distillery & The Famous Grouse Experience which has its dedicated water supply from the plant.
Among the largest drinking water plants in Scotland, Loch Turret Water Treatment Works was a direct filtration plant first put in operation in 1967 and designed to deliver water to a population of 70,000 . The main purpose of Scottish Waters upgrade was to install a new Actiflo clarification pre treatment process upstream of the existing rapid gravity filters to address the increasingly high peaks of raw water turbidity and colour in the loch. These raw water quality degradations adversely affected the operation of the rapid gravity filters and were unable to deliver the required throughput as they operated well below their design filter run time.
In addition to the new pre-treatment, further work was carried out to provide a new energy recovery turbine, Multiflo lamella sludge thickening, dewatering facility, chlorine contact tank and filtration media.
The Loch Turret upgrade was the largest drinking water project for Scottish Water in the latest investment period. The scheme was taken over in April 2010 and is now delivering 85 million litres of drinking water per day
Loch Turret WATER TREATMENT WORKS upgrade 2010 overview of the Actiflo main building and Multiflo lamella sludge thickening package plant.
Project Overview
The raw water source for Loch Turret WaterTreatment Works is characterised by relatively high colour from the peaty soil in the area. Over the years the geomorphology of the Loch and its catchment has led to periodic rises in raw water colour, natural organic matter and turbidity. These conditions are particularly acute following rainfall after a prolonged dry period and once snow starts to melt.
At the request of Scottish Water, Veolia Water Solutions & Technologies installed and operated a mobile Actiflo plant for a total of 4 months on site. The Actiflo delivered 1.2ML/d of clarified water which confirmed the ability of the process to treat effectively the water from Loch Turret. This step was essential to introduce the Actiflo process to Scottish Water and demonstrate the level of guaranteed performances.
The challenging ground conditions drove the need for a compact solution in order to minimise the excavation costs. In addition to the need for a limited footprint, a process capable of delivering a continuous high standard of clarified water quality, regardless of the raw water sudden characteristic changes, was essential to improve the operation of the existing rapid gravity filters.
To address the drivers for dissolved aluminium, true colour and turbidity, Veolia Water Solutions & Technologies provided the process design, construction, installation, testing and commissioning of 2 concrete classic Actiflo high rate clarifiers and 2 Multiflo Lamella Sludge Thickeners package plants. The Veolia scope of works included the sand storage and transfer system, polymer make up and dosing systems, coagulant, pH correction storage, associated dosing systems and software for the process.
Process Solution
The VWS technical solution centers upon the Actiflo process, which is ideally suited for difficult-to-treat sources with sudden variations of variable loads of Colour and Turbidity. Actiflo is a patented extremely versatile, high-rate, sand ballasted clarification system that effectively removes suspended solids and organic matter in surface water by coagulation / flocculation and lamella settling, achieving extremely low levels of outlet Turbidity and True Colour. Microsand (known as Actisand) is utilised as a seed for floc formation, providing a surface area that enhances flocculation and acts as a ballast or weight. The resulting sand ballasted floc enables clarifier designs with high rise rates and short retention times, having a typical footprint between 5 and 20 times smaller than conventional clarification systems of a similar capacity.
The comparison between Actiflo and its direct alternative DAF led to a CAPEX reduction of circa 60% while the OPEX remained similar.In addition to substantial investment savings, the Actiflo has the unrivalled ability to guarantee a consistent clarified water quality regardless of the raw water variations.
As a suitable treatment technology Actiflo is well proven with currently 561 references worldwide including 20 within the K.
Following the pilot plant results, the Actiflo proposal proved more cost effective than conventional alternative solutions. Close collaboration from day one with the end user and operators led to a reliable design providing the required instrumentation, standby facility and weather protection to operate successfully and comfortably in the challenging site environment.
The two Actiflo streams in operation each treat 50% of the design flow and are equipped with standby critical components. In addition to the level of safety built into the design, each Actiflo stream can treat the design flow of 85ML/d under exceptional conditions. The successful operation of the plant a year after the takeover and throughout the severe winter of 2009/2010 is strong evidence of the reliability of the process.
Attractive CAPEX
Although the Actiflo process is usually installed outdoors, uncovered, a building has been provided for security and to offer protection to the operating staff exposed to the severe weather conditions known to this location.
The drastically low retention time (2 and 6mn) associated with a settling area 5 times smaller than a DAF give Actiflo the benefit of a substantial price advantage.
Attractive OPEX
Like any chemically assisted clarification process, nearly 75% of the running cost is related to the use of coagulant. The power consumption of the Actiflo is lower than for a DAF plant which is penalised with the high demand generated by the 10% recirculation loop.
Loch Turret: Classic Actiflo OPEX distribution
The latest improvement i.e. Actiflo Turbo has since been developed and operates at the higher mirror velocity of 80m/h with minimised power consumption due to the introduction of the patented Turbomix system. This development has improved significantly the carbon footprint of the process and makes it highly competitive against high rate clarifications technologies.
Also available with green, biodegradable chemicals free of metals and polyacrylamides, the next generation of Actiflo Turbo is the most effective clarification solution which consistently provides an excellent treated quality with an even smaller footprint. With more than 20 Actiflo Turbo references, the latest Veolia patented innovations allow the high-rate ballasted Actiflo to operate as an Actiflo Carb to enhance organic matter removal using Powder Activated Carbon or as an Actiflo Softening to remove the hardness of any influent.
Loch Turret Water Treatment Works upgrade: a success story about integrated delivery
The Actiflo clarifier was the process solution of choice by Scottish Water Solutions who awarded the main contract to Galliford Morgan Joint Venture. The clarification and sludge thickening subcontracts were awarded to Veolia Water Solutions & Technologies as part of the upgrade to Loch Turret Water Treatment Works
This contract is a prime example of a successful collaboration from the earliest stage between the process contractor, civil company, client and consultant. The involvement of the operators from the pilot plant trial led the foundations for comprehensive communication between all parties, developing the design and commissioning in a truly collaborative way.
Focusing on the customer requirements while maintaining a transparent and open discussion at all time has been essential to the successful on time delivery of the project. Building on the technological advantages of the Actiflo process was only one step towards the completion of the scheme. Developing and fostering a collaborative spirit at every stage of the project life cycle made the difference and provided the best value proposition to Scottish Water.
