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Sludge wonderful sludge

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Back in 2009 Haigh were approached by a number of key customers with the request to bring a new small sludge screening system to the market. This opportunity was based on these customer’s desire to see genuine choice in this area, an alternative to the traditional spiral screw systems and a unit that would provide robust reliable performance with the unique features that Haigh’s popular range of ACE Screeners offer the market.

With the experienced in-house design and manufacturing capability that these customers value, Haigh were able to rapidly convert customer feedback and criteria into a prototype suitable for processing tankered sludge. A well-known local sludge tanker business in Leominster provided an ideal proving ground as they process sludge from an assortment of sources as well as municipal sludge and even local industrial and food processing. The aim was to process the input in such a fashion that it can be suitable for use as a fertiliser, while ensuring that the sludge screening system is as efficient and maintenance friendly as possible and minimising the peripheral requirements such as wash water and holding tanks.

Based on the ACE Screener design, with suitable optimisations for this specific application, the modular approach provided by Haigh delivered to the customer the combination of an automatically raked bar screen, maceration, Haigh’s liquid separator, and integrated flow control system, all following the company’s innovative approach to skid mounted plug and play installation. After extensive testing and configuration, the system further developed to ensure that no external process wash water supply was required, vastly reducing the operational cost of the system.

The properties of processing tankered waste gave specific challenges compared to the more constant flow received in a municipal inlet works environment, particularly as the solids content arriving at the screen could vary considerably through the course of each tanker emptying cycle, with considerably more solids being pumped out from the bottom of the tanker than from the top. Sawdust and bedding materials were a regular feature of the content of this concentrated part of the input, which needed to be processed on a regular basis, making the sludge at times exceedingly viscous. Haigh ensured that the unit was robust and reliable enough to manage processing this high load directly at all times, further reducing the costs associated with plant failure, based on a maximum delivery rate of approximately 25 litres per second to the screen.

As with the ACE Screener range, the solids output from the liquid separator proved to be compact and dry in nature, keeping the subsequent disposal of the unwanted material to landfill as efficient as possible. With elements of common componentry to the ACE Screeners, the product and spare parts for the unit can be kept as competitive as possible and have many years of design improvements from use in municipal inlet works already incorporated into them, based on the challenging performance and efficiency criteria set by the UK water sector.

Based on the success and product refinements achieved at Leominster, a further trial is under-way at a municipal site near Haigh where the unit is being exposed to higher daily usage and the types of sludge more typical of a general municipal site.

Haigh’s David Freeman comments “We would like to think that we have met our customer’s challenge of providing a genuine alternative to traditional sludge screening, while ensuring that our expertise from inlet works systems is reflected in the efficiency and reliability of this system.” Time and time again, the company’s innovative yet conservative approach to product development has proved to be a winning formula, providing solutions that are set apart from the generic processes already available. This development of both product and the complete integrated system enables customers to see a step change in performance characteristics compared to alternatives.

Following positive feedback at a recent open day hosted at Haigh’s Herefordshire based headquarters, attended by thirty farm operators, Haigh are looking to build a set of reference sites across the UK, launching the product both to private enterprises and adding it to the company’s portfolio of AMP 6 solutions for UK Water plcs.

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