For clean wastewater and a cleaner environment

Why do you need a grease separator?

During the processing or preparation of fatty foods, wastewater contaminated with fat, oils and food residues is produced, particularly in the catering and food industry. In Austria, this amounts to approx. 140,000 tons of fat per year. To prevent these contaminants from causing damage to downstream pipes, sewers and sewage treatment plants, they must be pre-cleaned. This pre-treatment (separation of impurities from the wastewater) takes place in grease separators.

The principle of operation of grease separators is based on the principle of gravity. By separating water, grease and dirt particles in the separator system, the wastewater is pre-cleaned (see image below).

Regular inspection, maintenance, emptying and cleaning are crucial for the correct and reliable functioning of a grease separator.

Competent maintenance of the system prevents malfunctions, unpleasant odors and damage to the system and in the pipes and ducts.

Legal basis:

In Austria, there are legal requirements for grease separators, especially in the catering industry and businesses with waste water containing grease. Here is the most important information:

Water Rights Act (WRG):

The WRG imposes an obligation to protect and keep waters clean. This is the potential basis for the obligation to install grease separators. These regulations stipulate that the quantity and harmfulness of wastewater must be kept as low as possible, taking into account the current state of the art(link to the law).

General Waste Water Emission Ordinance (AAEV):

It is issued on the basis of §33b of the WRG. This regulates the general limitation of wastewater emissions into watercourses and public sewers(link to the ordinance)

Indirect Discharger Ordinance (IEV):

It is decreed on the basis of §32 of the WRG. The applicable Indirect Discharger Ordinance (IEV) regulates the discharge of wastewater containing grease into the sewer system. Companies that produce wastewater containing grease must conclude an indirect discharger agreement with the sewerage company (e.g. clean water associations) (link to the ordinance).

ÖWAV Rule Sheet 39:

The revised Code of Practice 39 of the Austrian Water and Waste Management Association (ÖWAV) provides helpful and specific information for the practical use of grease separators. It describes the minimum requirements for wastewater pre-treatment with grease separation systems and is aimed at building owners, planners, operators and manufacturers(link to the code of practice)

EN 1825-2 (2002):

This standard is state of the art and specifies terms, nominal sizes, design principles, functional requirements, marking, testing and quality control for grease separator systems. This standard applies to separator systems for the separation of fats and oils of vegetable and animal origin from waste water by gravity without the effect of external energy.

Practical tips and tricks for operating a grease separator?

When operating a grease separator, there are some important points to consider in order to ensure that the system functions economically and properly. Here are the key points:

Responsible person:

• Every grease separation system should have a reliable person who is responsible for general supervision, maintenance and documentation.
• This person must receive training in the operation and maintenance of the grease separator.

Operating instructions:

• Observe the official and manufacturer-specific operating and maintenance instructions for your system. These may vary depending on the model and manufacturer.

Operating instructions:

• Operating instructions in German are required for every grease separator system. These should be kept to hand so that the responsible supervisor can operate the system in accordance with the regulations.

Regular maintenance and cleaning:

• Grease separator systems must be regularly inspected, maintained, emptied and cleaned. This ensures that no blockages form due to accumulated grease and sediment. A reliable person should be named in the maintenance log to ensure and document the general supervision of the operation of the system.

Control:

• The grease separator system should be checked at least once a month. Special incidents such as uncontrolled discharge of grease, sludge or waste water require immediate checks and documentation. The operating instructions serve as a guide for these inspections.

Avoid inlet temperatures above 60 °C:

• High temperatures can impair the functioning of the grease separator. Try to avoid inlet temperatures above 60 °C.

Separator-friendly cleaning agents:

• Use separator-friendly rinsing and cleaning agents. These should not form stable emulsions and should not impair the separation of grease and water.
• The use of biological or chemical agents for self-cleaning of the grease separator system is not permitted. Comply with the applicable regulations.

Remember that proper maintenance and operation of your grease separator system is not only required by law, but also helps to protect the environment and prolong the life of the system.

What problems can arise when operating a grease separator?

Grease separators are often indispensable for removing grease and oil from wastewater and relieving the burden on sewer systems and sewage treatment plants. However, various problems occur time and again during operation – here are the most common ones:

Constipation:

• Disposal of kitchen waste via the sewage system or the grease trap is prohibited. This waste must be collected and treated separately.
• One of the most common problems with grease separators is blockages caused by accumulated grease and sediment. To avoid this, it is important to regularly remove the collected grease and clean the separators accordingly.

Emulsified fat:

• Although a grease separator can retain coarsely dispersed, directly separable grease, it cannot retain finely dispersed, emulsified or dissolved grease from the waste water. This can lead to problems, especially if the pre-cleaning of plates and containers and the pre-rinsing with cold water are not carried out correctly.
• The rinsing and cleaning agents used should be separator-friendly and not form stable emulsions.

Difficulties with introduction:

• In practice, difficulties can arise when installing grease separators (especially when retrofitting). The installation routes (access roads, hallways, corridors) can be too narrow or too winding, and the openings (doors, gates, shafts) too small.

Damage to the inside of pipes:

• The decomposition of grease in waste water leads to sluggish gases and acids that attack the inside of the pipe and, in the worst case, can break through.

Regular maintenance and cleaning of grease separators is essential to reduce the likelihood of these problems occurring, keep operating costs low and ensure that the system functions reliably.

What needs to be considered when maintaining a grease separator?

The frequency of maintenance measures for grease separators depends primarily on the type of operation, the size of the grease separator and the amount of grease-laden wastewater. The following tasks are associated with this:

Inspection:

All system components must be checked as required, but at least once a month (in accordance with ÖWAV regulation sheet 39) and after all special incidents (e.g. storms, malfunctions). This can be carried out by a trained operator. The following tasks must be carried out:

• Measure the sludge height in the sludge trap Dispose of sludge if necessary
• Measure the thickness of the grease layer Dispose of grease if necessary
• Entry in the maintenance logbook

If the sludge layer thickness in the sludge trap or the grease layer thickness in the grease separator specified in the operating instructions has been reached, then an evacuation must be initiated.

Clearing / cleaning:

An authorized company is to be commissioned with the clearance and, if possible, also with the maintenance, which is liable for compliance with this regulation.

The clearing intervals must be set in such a way that the storage capacity of the separator is not exceeded and its functionality is not impaired. Grease traps and sludge traps must be completely emptied at least every six months. When emptying, the sludge trap and grease trap must be completely emptied, then cleaned and filled with fresh water before being put back into operation.

The debris must be disposed of in accordance with waste disposal regulations. Proof of clearing (invoice with details of the quantities disposed of) must be filed in the maintenance log or made available for inspection by the authorities.

Maintenance:

Annual maintenance is clearly recommended and is mandatory for many manufacturers according to the operating instructions and forms the basis for their warranty. Maintenance is usually carried out after cleaning and emptying the grease separator so that the technical components (e.g. seals, shut-off valves) can be easily reached. This ensures optimum functionality and prevents disruptive blockages.

Checking the wastewater quality:

The inspection should be carried out BEFORE an evacuation by suitable experts as a qualified random sample (under no circumstances immediately after cleaning) so that the cleaning effect can be determined during normal operation (the wastewater sample is usually taken from the sampling shaft). The samples are usually analyzed for temperature, settleable substances, pH value, COD, semi-volatile lipophilic substances. The sewerage company can specify further tests – the sample result must be submitted afterwards without being asked.

Documentation:

Remember to document all maintenance and cleaning work in the maintenance log. This is required by law and serves as proof that the grease separator has been properly maintained.

Maintenance – as so often the basis for a long system life

As you can see, with just a little effort, regular inspection of the system can be carried out quickly and easily with a little know-how and interest. However, emptying, disposal, maintenance, cleaning, repairing damage and adjusting the system clearly belong in the hands of a specialist company.

Regular inspection and maintenance is definitely a must if you want to use the system economically for a long time, as this usually reduces faults significantly and considerably extends the service life.

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