June 23, 2024

Environmental Effect of FOG

There are three grease interceptors; passive hydromechanical (manual), automatic and gravity grease trap. The passive one is the most common among the three ideal for small commercial eateries. The economic cost of installation and wide spectrum of size, smaller one e easily fit under the sink, and larger are apt to manage the larger wastewater system. The design of the hydromechanical grease trap was intended in 1885 with a US patent. The design remains unchanged, mostly manufactured from stainless steel or plastic idyllic for basic operation. The interceptor can be manually cleaned regularly.


AGRU (automatic grease removal units) work on a principle similar to a manual one, except it heat and skim out accumulated FOG at regular intervals as programmed. The skimmed FOG is conveyed in a bin for easy disposal and recycling. The program depends on the amount of FOG produced by the establishment, and technicians don`t have to manually check the grease level. They come in various shapes and sizes to meet various requirements. Despite the high initial cost, it is more effective and lowers maintenance and operation costs.

Gravity Grease Traps

Gravity grease traps are usually underground chambers made of concrete, steel or fiberglass. The mechanism is identical to AGRU but with higher storage and wastewater treatment capacity. The grease traps need to be vacuumed by grease trap pumps by maintenance technicians for optimal operation. Some municipalities lay down the interval of grease trap cleaning, and the document needs to be submitted to the appropriate jurisdiction and kept on the site.

Reduces DO

The untreated FOG (fat, oil and grease) does not mingle with water but floats, forming a thin layer. This FOG layer clogs the city’s main sewerage system as it is fluid at high temperatures but solidifies at a lower temperature. When FOG enters a water body (drain, pond, river, canal or lake), it suspends above the water, blocking sunlight to penetrate inside water. The mirrored sunlight blocks the supply of photons in water, stopping the natural production of dissolved oxygen (DO). This negatively impacts the marine life of the water body. The untreated FOG waste from household and commercial eateries has a huge environmental effect.

Ripple effect 

But this is not the end of the effect but stimulates a ripple effect on the water body. Due to the low level of dissolved oxygen, aquatic life suffocates, and anaerobic life thrives and anaerobic digestion. The byproduct of this process produces hydrogen sulphide, causing a pungent smell in the area. As the water flow stagnates, mosquito larva becomes the breeding ground, increasing the potential threat of vector-borne diseases such as malaria, dengue, and chikungunya. Consequently, there is algal growth aggravation of the water decomposition. The colour of water changes from natural to dark green, then to grey and ultimately to black, appearing like scorched automobile engine oil. 

A grease trap aims to reduce the FOG level entering into main sewerage lines. Increased level of FOG in main drainage system escalates pest infestation, foul smell and clogging. Grease traps are designed for FOG waste generated from kitchens but not to treat waste from toilets. The grease interceptors are made from concrete, plastic, stainless or mild steel with capacity ranging from 40 liters and 45000 liters and above.