Sources of odour include ponds, tanks, solids separation systems, sludge piles, feed pads, and silage stacks. Effluent application, the desludging of ponds and muck spreading operations also release odour.
If the regional council receives a complaint about an odour, the council will come out to your farm and assess the situation. Infringement /abatement notices may be a potential consequence.
Identifying the issue and source
If a neighbour complains about an objectionable odour or you notice some issues yourself you must investigate further. This is not generally a problem that disappears quickly. Often the main culprit is the effluent storage pond although it does pay to check that there’s not a problem with effluent stored in the main lines.
If you’re satisfied that the issue is the storage pond itself, try and diagnose the type of smell using the table below.
|Hydrogen Sulphide||rotten eggs|
|Methyl Mercaptan||decayed cabbage, garlic|
|Ethyl Mercaptan||decayed cabbage|
|Dimethyl Sulphide||decayed vegetables|
|Volatile organic compounds||varies between compounds - solvent type/putrid/sickly|
You can also tell a lot about a pond from its colour. Click on the relevant section below to gauge what’s happening in your pond.
A green looking pond is usually in good condition and should not produce any objectionable odour, apart from very occasional episodes. If there is however a green scum on the surface then this is likely to be blue green algae and this may increase in population and then die off suddenly releasing toxins and odour.
A black–greyish pond can be a sign of a high sludge level and highly concentrated effluent in the pond causing anaerobic activity.
A pink pond that is bubbling is a sign of the establishment of purple sulphur bacteria (PSB). PSB mitigate odour release by using sulphur to respire and thereby reducing the amount of hydrogen sulphide produced. Such a pond is most likely recovering from an odorous period so there should be little odour from a light pink pond.
This colour is likely to be due to an increased anaerobic activity as the water temperature rises. The release of sulphide and hydrolysis products is likely to turn the water milky and smelly.
This colour is likely to be caused by an excessive proliferation of cyanobacteria. This will lead to the release of bad smells and the production of toxins in the water. Cyanobacteria may bloom with warm temperatures and high nutrient levels. It is a sign that the pond is receiving a high organic loading. Treatments include aeration/mixing, hydrogen peroxide, and possibly algaecides. Expert advice from a waste water treatment engineer may be needed if this is occurring in the pond.
What is causing the pond to smell?
Odours from ponds are caused by a mixture of gases. The type of pond and the way the pond is operated and maintained impacts on odour production. These gaseous compounds are produced all the time but usually at low levels that are not an issue.
However, occasionally they get out of balance and produce an ‘odorous’ episode. There are a variety of reasons for this, these include overloaded or shock-loaded pond systems and seasonal climatic conditions, click here for more detailed information.
Keeping the neighbours happy
If you are planning an activity you know will generate some odour, such as spreading a large solids pile or desludging a storage pond, consider these handy tips:
- Schedule effluent activities from Monday to Thursday to avoid odour immediately before the weekend.
- Spread effluent in the morning to take advantage of warming conditions which help disperse the odour.
- Avoid spreading when the wind is blowing towards the neighbour
- Let the neighbour know when you are planning some activities. If they know they are likely to be more accommodating (and appreciative of your thoughtfulness). They may be planning an outdoor event in which case you might be able to reschedule spreading to another day.
- Note - it can take a couple of days for the odour to disperse after spreading.