Trade Waste
Hastings District Council sets limits on potentially harmful substances which business may discharge into the wastewater system.
This is done through Trade Waste Consents. All businesses discharging more than 10,000L per day of waste water must have a Trade Waste Consent.
Smaller businesses discharging less than 10,000L per day are considered a “Permitted activity” and no consent will be required provided that the discharge complies with Schedule 1A (PDF 565kB) of the Water Services Bylaw
Why do we need to control the waste from food related businesses?
Food related businesses such as Takeaway shops, restaurants, butcher shops, cafes, bakeries etc – in fact any small business that processes food on the premises is likely to discharge oil and grease into the city’s waste water system.
Oil and grease can solidify and cause blockages, resulting in sewer overflows, hazards to public health and pollution of the environment.
What happens if my business causes a restriction or blockage in the waste water system?
Where the business causing restriction or blockage is identified it may be charged for the cost of the inspection, clearing the blockage and any clean up costs.
The Council has a duty to protect the community-owned waste water disposal system and treatment facilities, and to protect people and the environment.
How much oil and grease can be discharged into the waste water system?
A maximum of 30 mg/l of floatable oil and grease may be discharged into the waste water system.
The reason for the low allowable level is due in large part to how flat the city of Hastings is.
Our waste water system does not have many hills to run down, so the waste water flows more slowly and is therefore at more risk of build ups of grease in the pipes.
What happens if my business discharges more oil and grease than allowed in the Bylaw?
Any greater amount than 30 mg/l means the discharge does not comply with the Water Services Bylaw.
Council will work with the business operator to bring the discharge into compliance. Failing to cooperate with the Council within a reasonable timeframe to bring the discharge into compliance may result in the wastewater connection being terminated.
How can I reduce the amount of oil and grease entering the waste water system?
The most common method of reducing the level of oil and grease from entering the waste water system is by installing a grease trap.
What is a grease trap?
The most common grease trap design is simple non mechanical device that captures the oil and grease that is present in the waste water generated by the business.
The trap is installed in the ground; it has an inlet, an outlet and baffle walls which separate the unit into a number of chambers. In the chambers, solids settle forming a sediment layer, with most of the oil and grease floating to the top.
Is there more than one type of grease trap available?
There are several types of grease traps available. The most important consideration is the size of the grease trap. The size must be matched to the volume of waste water discharged from the business.
Installing a trap that is too small for the volume of waste water is likely to result in a significant amount of the oil and grease flowing through the trap and entering the waste water system resulting in a “non compliant discharge”.
What size of grease trap do I need for my business?
HDC recommends the following grease trap sizes
- Minimum size for any premise 1000L
- Takeaway premises, bakeries etc 1000L
- Restaurants up to 50 seats 1000L
- Restaurants 50 up to 100 seats 1500L
- Restaurants over 100 seats 2000L
The sizes recommended by HDC vary from the sizes recommended in the Acceptable Solutions G13/AS2.
The sizes recommended in G13 are in most cases not sufficient to meet the levels allowed in the HDC Trade Waste Bylaw.
Do I need to maintain the grease trap?
Yes. As solids (food scraps), oil and grease collects, the trap becomes less efficient. When approximately 25% of the working depth of the trap is taken up by the layer of solids, floating oil and grease layer, the trap should be cleaned. Once the trap has been cleaned it should be filled with cold water to ensure proper operation.
You must record the date of cleaning, the name of the contractor/person carrying out the cleaning, the waste tracking number provided by the contractor and the disposal site of the grease waste. Each record must be kept for a period of two years to comply with the Water Services Bylaw.
At the time of cleaning the trap should be checked for any faults.
You will need to have the record of cleaning available for inspection upon request by council representatives.
How will I know when I need to clean the grease trap?
By monitoring the grease trap to establish when it needs cleaning. The frequency of cleaning will vary based on the size of the trap and the amount of oil and grease generated by the business.
What happens if I do not clean the grease trap?
Council representatives will inspect all grease traps at least once each year. This inspection is not charged for. Should the grease trap and/or the records of the grease trap cleaning be less than satisfactory at the time of inspection, another inspection will be carried out a short time later.
The second inspection may be charged for at the rates published in the HDC Annual Plan.
If the grease trap is not clean on second inspection then council will instigate a regular programme of inspections of the grease trap and all additional inspections will be charged for at the published rates.
The frequency of the inspections will depend on the type of business in question.
What can I do if there is no room to fit a grease trap?
There are other types of grease traps available and can be equally effective if correctly matched to the waste water volume and correctly maintained. The most common would be an enzyme grease converter.
The grease converter is a tank that traps the oil and grease much like a grease trap does. The tank can be installed inside the building, usually under the kitchen sink or close by.
A grease converter is a good option where a grease trap can not be fitted.
How does the grease converter work?
The grease converter works by regular dosing with enzymes that breaking down the oil and grease trapped in the tank. Using the correct enzymes and correct dosing is vital for effective operation of the grease converter.
What size grease converter do I need?
The grease converter needs to be sized to match the peak volume of waste water discharged by your business. You will need to discuss your requirements with the manufacturer or supplier.
It is very important that you follow the manufactures recommendations regarding the peak loading and correct enzyme dosing to ensure proper function of the grease converter and ensure your waste water discharge is compliant with the HDC Water Services Bylaw.
Can my business use a Waste Master or waste grinder to dispose of food scraps?
No. Waste Masters or waste grinders of any kind are not permitted under the Water Services Bylaw in any business premise.
It is important to reduce the amount of solids (food scraps) entering the grease trap or grease converter. This can be achieved by installing easily cleanable screens that remove most solids before the waste water enters the traps.
This is very important in the case of grease converters since solids reduce the effectiveness of the enzymes used to break down the fat.
Solids build up in the grease trap and reduce the effectiveness of the trap and can result in the trap becoming anaerobic and emitting foul smells. Regular cleaning will help avoid this.
Do I have to install a grease trap or a grease converter?
Yes. In the Acceptable Solutions G13/AS2 to the Building Act it is stated: In buildings other than housing, grease traps shall be provided where the waste water is likely to convey grease.
Why does HDC recommend much bigger grease traps than The Acceptable Solutions G13/AS2 stipulates?
Your business can comply with the Building Code by installing a grease trap that is sized according to the code. However, the grease trap sizes in the code would not be effective enough to meet the limits allowed in the HDC Trade Waste Bylaw.
What if I want to spend less money and buy smaller grease trap or grease converter?
It is up to each business to choose what to do. Even a small grease trap or grease converter will reduce the amount of oil and grease in the waste water discharged from your business.
While smaller is cheaper, you will need to clean them more often, costing more per year to maintain and the amount of oil and grease in your waste water discharge is more likely to have higher-than-allowed limits, resulting in non compliant discharge and defeating the purpose of installing one in the first place.
My business has already got a small grease trap – should I install a bigger one?
The short answer is yes. Consistently good housekeeping may keep your discharge within allowed limits even if you have a small grease trap – the question is; do you have time to do the right thing all the time? Is it worth taking the risk of having a non compliant discharge?
Need more information?
Contact the Hastings District Council Trade Waste Officer on telephone (06) 871 5000