Context

The client

Tipperary Cooperative Creamery in Ireland processes around a million litres of milk daily, producing around 60,000 tonnes of cheeses, butters, milk powders and other dairy products every year to be sold in Ireland and across Europe, UK, USA, Middle East and Asia.

Treatment plant upgrade

As part of a major programme to reduce water consumption, waste production and energy use, an upgrade was required to its existing waste water treatment plant using best-in-class technology and processes.

Part of that upgrade was the odour control plant.

The existing odour control plant

The existing odour control system was designed to treat 7500 Nm³/h of air.

Two centrifugal fans operating as duty and standby extract air from the production areas and blow it upwards through an odour control unit to be discharged via a stack into the air.

The odour control unit consists of a tank containing 33 m³ of mussel shells media supported on a layer of clam and oyster shells.

Water is continuously circulated from the bottom of the tower to spray distributors at the top which give even distribution over the media.

Bacteria in the circulating water biologically remove the odour-producing contaminants.

Work done

Testing of the odour control system

When MEHS checked the odour control system, they found the air flow was only 600 Nm³/hr, a significant order of magnitude below the design figure.

After opening the unit, it was found the system performance was affected by the mussel shell media breakages, which had reduced voidage to such an extent that water hold-up, or ponding, was occurring which was impeding the flow of air through the media and reducing the efficiency of the process.

Installation of new media and pH control system

MEHS removed the old media, power washed the scrubber and installed two types of new media designed and manufactured by Warden Biomedia: 1.8m depth of Bioflo+ supported on a layer of Bioball 0.3m.

MEHS also installed an automated pH control system to control the pH between 8.5 and 9.5.

The Outcome

After adding the new media, the water recycle was re-started and concentrated bacteria added to system.

The air flow was checked at 7,500 Nm³/hr and the inlet and outlet flow sampled for odorous parameters by SOCOTEC UK, an accredited laboratory.

The odour concentration on the inlet was 25,747 OUE/m³ and the outlet odour concentration was 350 OUE/m³ – a 98.6% reduction of the odour concentration.

Results – Inlet & Outlet Concentrations

Parameters

Units

Inlet

Outlet

Amines

mg/m3

15

0

Ammonia

mg/m3

3

0

Hydrogen Sulphide

mg/m3

25

1

Mercaptans

mg/m3

2

0

The media have a high surface area, which is important for contact between the liquid and gas, but also means a low pressure drop, minimising fan power. Whilst the cost of the new media was similar to the replacement of the shell media, the plastic media are durable with high resistance, therefore unlike the shells, the media will not need to be replaced.

The client is very happy with the odour control system.

The Consultants

Trevor Montgomery of MEHS has worked with Warden Biomedia for over a decade and knows their products well. MEHS was responsible for the design, supply, installation and commissioning of the plant.

“Bioball is the perfect media for a bioscrubber. It has a surface area of 220 m2/m3, which is important for contact between the liquid and gas, but it also has 95% voidage which means a low pressure drop on the gas side and that minimises fan power.”

MEHS was awarded a 5-year service contract to remote monitor the plant every day and make a monthly site visit.