About the Facility

Scientists will use BEWISe to run experiments exploring different types and combinations of bacteria to identify how they behave in different sewage treatment processes.

Northumbrian Water has 413 sewage treatment works across the North East region which treat around 800 million litres of wastewater every day. Birtley sewage treatment works treats up to 10,000 million litres of wastewater a day.

On average, each of us generates 135-180 litres of sewage a day. Over 99.9% of sewage is liquid, with less than 0.1% solid.

One of the most commonly used traditional sewage treatment process is activated sludge:

• settled sewage enters the aeration tank, where the wastewater is aerated and bacteria use the organic pollution in the wastewater as food and start breaking it down
• after several hours, the bacteria (the so-called ‘activated’ sludge) are separated from the treated water in a clarification tank
• the treated water can be further ‘polished’ or sent to re-enter the water network through rivers
• part of the sludge is returned to the aeration tank

Birtley sewage treatment works uses trickling filters, which is less energy intensive. Wastewater filters through a waste product from the steel industry (known as blast furnace slag) and is also treated by bacteria.

The BEWISe facility has both activated sludge and trickling filters as well as two novel treatment systems that capture energy from the wastewater.

Standard sewage treatment accounts for up to 1.5% of UK electricity usage, much of it for aeration. The water industry generates 4 million tonnes of CO2 per annum, which accounts for 0.7% of UK greenhouse gas emissions.

Over £100 billion has been invested in standard sewage treatment processes since 1998. Existing technologies have very long design lives (25-50 years). Thus, it will take at least a generation (2030 and beyond) for their replacement, whereas the biology may be changed on shorter timescales.

The UK water industry is expected to spend £28 billion in energy-intensive wastewater treatment technologies to meet new environmental standards.

Activated sludge tanks

The facility houses two Activated Sludge (AS) tanks with connecting secondary clarifiers, constructed from HDPE (high-density polyethylene). They are each mounted onto a stainless steel skid.

• AS tanks: 1.7m height × 1.2m width × 1.5m length
• clarifiers: 1.8m height × 0.3m width × 1.6m length

The AS tanks receive wastewater via pumps. These are taken off a ring main flowing with either settled sewage or raw sewage from the main Birtley treatment works.

The wastewater enters the aeration tank. Here, organic pollution in the wastewater is broken down when used as a food source by bacteria.

After several hours, the bacteria (the ‘activated’ sludge) separates from the treated water in the secondary clarification tank by settling. Part of the settled sludge is recycled into the AS tank. The rest is pumped out to waste.

The treated effluent flows over the top of a weir and back into the Birtley treatment works.

Both the AS tank and secondary clarifiers have a handful of ball valves to take samples from key areas of interest.

The advantage of an AS system is that it can treat large volumes of water and takes up relatively little space. The disadvantage is that it needs a large amount of electricity to continuously run the aeration.

Trickling filters

The facility houses two cylindrical Trickling Filters (TF) approximately 2m high by 1m wide with connecting secondary clarifiers similar to those on the AS. They are constructed from HDPE and mounted onto a stainless steel skid each.

Each TF tank has removable baskets filled with plastic filter media inside. The baskets are removable so that we can sample and replace the filter media as necessary. The filter media provides a large surface area on which bacteria can grow.

As with the AS systems, wastewater is taken off the ring main via pumps. Wastewater is fed from the top by a slowly spinning pipe. It then trickles down the whole length of the filter media on which the bacteria grow. The bacteria use the organics in the wastewater as a food source to grow, with excess bacteria separated out in the clarifier just as in the AS.

The advantage of the trickling filter system is that it requires very little power. It is naturally porous and does not need engineered aeration. The disadvantage is that, compared to the AS system, it can’t treat the same volumes of water and takes up a lot of space.

We have the following facilities available:

• activated sludge
• trickling filter
• upflow anaerobic sludge blanket (UASB) technology
• microbial electrochemical fuel cells
• adaptable polishing tanks (eg wetlands)

Key features of the pilot plants