Dale Foster and Adrian Heneghan from specialist wastewater treatment technology provider HUBER Technology discuss why the company is shifting its focus to meet growing demand from UK wastewater companies for its advanced fine screening solution for Membrane Plant Protection.

Dale Foster and Adrian Heneghan: Stringent UK environmental regulations and ever tighter water quality standards are continuing to drive UK water sector investment in the UK and accelerating membrane bioreactor adoption. We’re seeing the advent of more projects in the UK & Ireland involving various types and designs of membrane plants for wastewater treatment to meet regulatory compliance and reduce operational costs. As a result, we’re seeing an uptake in demand for our HUBER Drum Screen Liquid (DSL) advanced fine screening solution for membrane plant protection.

The HUBER DSL was initially launched in the UK & Ireland as a replacement for conventional Primary Settlement Tanks (PSTs), or as a solution to increase settlement capacity on sites where insufficient space was available to construct conventional PSTs.

While membrane plants are already widely used in the clean water sector, there is also growing potential uptake in the wastewater sector. We’ve certainly seen this in HUBER’s markets outside the UK, including installations in Australia, Germany and Switzerland. 

In the UK, our strategy has now shifted to an increasing focus on three key applications for the HUBER DSL:

• The protection of sensitive membrane technology

• ‘Polishing’ flow from river/water intakes.

• Fine screening of stormwater or additional flow to treatment works as part of modular sidestream/treatment train solutions. Other HUBER products, such as the HUBER ROTAMAT® RoK1 & RoK2 Stormwater Screens, RotaFilt® Pile Cloth Media Filter and RoDisc® can also be utilised in this area of treatment.

While we have other HUBER fine screening options available, for membrane technology, we’re finding that the HUBER DSL is leading the way where high flow volumes can be accommodated using fewer units. Prior to membrane filtration, membranes must be protected from large solids to ensure optimum operational performance. For this purpose, two-dimensional separation of solids with a screen with between 1 and 2 mm perforations is considered optimal.

We’re currently working on a number of projects involving membrane protection screens, including an early trial DSL unit installed at Welsh Water’s Trebanos Wastewater Treatment Works to prevent anything greater than two millimetres from getting into the outfall by diverting 20 litres a second of stormwater. While it’s still at an early stage, results to date have been excellent. Please contact us for further trial data.

Membrane plants are very sensitive items of equipment which require filtration down to at least one millimetre which the DSL provides – and the DSL can go a lot lower than that. With more membrane plants now being put in around the UK or under consideration, the wastewater companies are looking for screens to protect those membranes. If the membranes aren’t properly protected, damaging solids can get through causing blockages and serious problems.

As far as regulatory compliance, the majority of specifications are mainly for inlet screens. However, currently there is relatively little compliance or even regulation when it comes to providing screens for membrane protection.

Inlet works play key role in protecting sensitive membrane plant processes

At the moment the industry predominantly use band screens for these applications. However, the problem with band screens is that they're fairly limited on hydraulic capacity and they also require additional launders and compactors. Standard compactors are generally fitted with 5 or 6 mm perforated/slotted baskets which can lead to fine solids removed by the screens being pumped back to the head of the works, where some of the solids are likely to pass through the 6 mm inlet screens.

A potentially serious problem – the concern being that when wastewater companies install membrane plants and membrane protection screens, the inlet works could be at risk of falling into disrepair. Membrane plants are ultra-sensitive processes which the companies are looking to protect - ensuring that existing inlet works are maintained correctly have a key role to play in this.

It’s also important to bear in mind that the wastewater companies’ treatment train solutions are seeking to put more flow through the works instead to relieve the CSOs upstream in the network.

The HUBER DSL can be used to protect membranes on that side stream application and also be used as a primary tank there where there won’t be any ferric dosing.

Majority of UK water companies considering using MBRs to help address water quality requirements

The majority of the UK water companies are now considering using membrane technology to help them address water quality requirements with regard to discharging to watercourses and other surface waters. The membranes will clean up the water, backed up by UV treatment, to almost potable water standards.

Currently the three main membrane technology players are DuPont, Suez and Veolia. They are all different membrane systems, but they are doing the same job. The DSL is eminently well suited for all of them – the beauty of the DSL is that we can go lower than 1 millimetre. So if the membrane suppliers say that they want, let's say less than 1, 0.75 or 0.5 millimetre then we can do that as well. We can go lower if needed - down to 200 microns if necessary. So where the wastewater companies are putting more flow through the works instead of spilling and CSOs, using the DSL will enable them to replace primary settlement tanks and use the DSL as tank mounted primary tanks with a 10^th of the footprint.

In terms of technical specifications, the HUBER DSL comes in a range of options:

1300, 1600 and 2200 mm drum diameters are available, with different drum lengths and numerous aperture sizes.

Screen apertures

• Woven mesh: 0.2 - 0.75 mm
• Wedge wire: 0.5, 1, 2 and 3 mm
• Perforated plate: 1, 1.5, 2 and 3 mm
• Star folded perforated plate: 1 and 1.5 mm

Tackling the effects of FOG

To combat the worst effects of fats, oils and grease (FOG), the HUBER DSL is fitted with an innovative automatic high-pressure system generating 120 bar pressure. We recommend this for all projects in the UK & Ireland. FOG captured by the HUBER DSL is washed from the drum and discharged into a launder inside the drum, feeding a dedicated screenings handling plant.

Solids handling

The HUBER ROTAMAT® Micro Strainer Ro9 fitted with 0.5 mm wedge wire baskets is our solution. Standard compactors are generally fitted with 5 or 6 mm perforated/slotted baskets. This can lead to fine solids removed by the screens being pumped back to the head of the works, where some of the solids are likely to pass through the 6 mm 2D inlet screens and be dealt with by the HUBER DSL again.

Although finer solids may settle out in the PSTs, it is better to remove and isolate these solids, which contain membrane-damaging hair and fibre, when they are captured, avoiding a degree of recirculation.

To sum up, for wastewater companies looking to install Membrane technology, HUBER’S DSL will provide them with peace of mind when it comes to protecting these sensitive plants.

Further product information can be seen on our website - HUBER Drum Screen LIQUID | HUBER Technology

For more information or for an informal chat about the DSL and its capabilities, contact:

Dale Foster - Business Development Manager for Huber Technology at This e-mail address is being protected from spambots. You need JavaScript enabled to view it or mobile +44 7980 316059 

Adrian.Heneghan - Business Development Manager for Huber Technology at This e-mail address is being protected from spambots. You need JavaScript enabled to view it or mobile +44 7540 667094