In the seafood processing industry, oil and grease are always among the most challenging components in the wastewater treatment process. Not only do they reduce the efficiency of treatment facilities, but oil and grease also trigger a series of problems such as floating sludge, poor microbial activity, equipment fouling, increased operating costs, and the risk of effluent not meeting standards. If this situation persists, the negative impacts will not just stop at the treatment system but will also directly affect the surrounding environment. Understanding the impacts of oil and grease will help businesses become more proactive in their operations, thereby maintaining stable treatment efficiency and minimizing arising risks.
Compared to many other industries, seafood wastewater often contains high levels of oil and grease generated from the preliminary processing of raw materials, filleting, steaming, frying, canning, and cleaning of production equipment. This component includes fish oil, animal fat, and various organic substances mixed with suspended solids and proteins, creating a relatively difficult-to-treat mixture.
In actual operation, the oil and grease content in seafood wastewater often fluctuates depending on the type of raw material, season, and production capacity. When the pretreatment stage fails to remove most of the oil and grease, the pollution load will continue downstream, increasing the pressure on the biological tank and many pieces of equipment in the system.
Therefore, oil and grease are not just parameters that need to be controlled but are also factors that can cause a chain reaction affecting the entire wastewater treatment system. From the initial sludge separation stage to the biological tank and mechanical equipment, every category can suffer a decline in efficiency when the oil and grease load exceeds treatment capacity.
.jpg)
Seafood processing stages generate a lot of oil and grease in the wastewater treatment system.
Oil and grease do not just cause difficulties in a single stage but can affect the entire wastewater treatment process. From the pretreatment system and biological tanks to mechanical equipment, efficiency can decline when the amount of oil and grease exceeds control capacity. Below are common impacts that many businesses often encounter during operation.
Pretreatment is the first "barrier" that helps reduce the load on the entire system. However, when the oil and grease content is too high, the efficiency of this stage often drops significantly.
Oil and grease can coat suspended solid particles, changing the characteristics of the flocs and reducing the efficiency of the coagulation and flocculation process. For systems using DAF (Dissolved Air Flotation) tanks, oil and grease also reduce the adhesion between air bubbles and flocs, causing pollutant separation efficiency to fall short of the design.
In reality, many plants have to increase the dosage of PAC or Polymer to maintain flotation efficiency when the influent oil and grease load fluctuates seasonally or when processing output surges. This not only increases chemical costs but also allows the organic load to continue into the biological treatment facility. When oil and grease are not effectively removed in the initial stage, the treatment pressure shifts to downstream facilities. This is also why biological treatment efficiency begins to decline.
After the pretreatment stage, the remaining oil and grease will follow the water flow into the biological tank. Here, oil and grease can adhere to sludge flocs or form a film on the water surface, reducing oxygen diffusion and hindering contact between microorganisms and pollutants.
When the microorganisms' habitat is affected, the decomposition rate of organic matter decreases, making it difficult to maintain stable effluent COD. At the same time, the nitrifying bacteria group may also experience reduced activity, meaning Ammonia treatment efficiency no longer meets the design.
In actual operation, many systems record abnormally high COD or Ammonia even though the wastewater flow has not changed significantly. Besides checking the influent load or aeration regime, businesses also need to assess the accumulation of oil and grease in the system to determine the exact cause.
When this situation is prolonged, the microbial system not only loses its capacity to treat organic matter but also alters the structure of the sludge flocs. This is also the cause of poor sludge settling or floating sludge, phenomena commonly encountered in seafood wastewater treatment systems.
Oil and grease adhering to the surface of sludge flocs reduce their specific density, making the flocs lighter. The consequence is that the sludge becomes hard to settle, easily floats to the surface, or gets washed out of the secondary clarifier with the water flow.
As sludge loss increases, the MLSS concentration in the biological tank gradually decreases, impairing the treatment efficiency of organic matter and nutrients. Businesses may have to supplement activated sludge or spend a lot of time recovering the microbial system after an incident. The phenomenon of floating sludge also increases the volume of sludge that needs to be collected and treated, driving operating costs ever higher.
In addition to chemical costs, many businesses also have to increase the frequency of cleaning flotation tanks, flushing pipes, or maintaining pumps due to prolonged oil and grease adhesion. These are incurred costs that are often hard to notice immediately but significantly impact the overall operating cost of the system.
When oil and grease accumulate over a long period, they tend to stick to tank walls, pipes, pumps, air diffusers, and many other mechanical devices. This reduces operational performance, increases the risk of blockages, and shortens the lifespan of the equipment.
Concurrently, businesses often have to increase the amount of chemicals used for coagulation, flotation, or equipment cleaning. Maintenance frequency also increases to limit incidents and ensure the system operates continuously.
For plants with large wastewater flows, these incurred costs can account for a significant proportion of total monthly operating expenses. Therefore, controlling oil and grease right at the source always yields higher economic efficiency than dealing with incidents after the system has already been affected.
Not only does it increase operating costs, but excess oil and grease can also cause many environmental consequences if the wastewater is not treated satisfactorily before discharge.
.jpg)
Oil and grease sticking in pipes during discharge.
Not only do they affect treatment efficiency, but oil and grease are also agents that exacerbate environmental problems if wastewater is not well-controlled before discharge. These impacts affect not only the receiving source but also increase the risk of violating environmental protection regulations and incur significant remediation costs for businesses.
If wastewater containing high levels of oil and grease is discharged into the environment without adequate treatment, the oil and grease will form a film on the surface of the water source. This film hinders oxygen exchange between the air and water, reducing dissolved oxygen levels and affecting the development of aquatic life.
Over time, the quality of the receiving source can decline, especially in rivers, canals, or ponds with low flow rates.
Oil and grease accumulating in treatment facilities easily decompose under anaerobic conditions, producing odor-causing compounds such as H₂S, NH₃, and volatile fatty acids. This is why many seafood wastewater treatment systems generate unpleasant odors at collection areas, equalization tanks, or grease traps.
If left uncontrolled, odors not only affect the working conditions of employees but also impact nearby residential areas, especially for plants located near urban zones.
Oil and grease are among the parameters controlled in many wastewater standards. In many cases, oil and grease not only exceed their own specific limits but also indirectly affect COD, TSS, and related indicators because biological treatment and settling efficiencies both decline.
Effluent wastewater failing to meet standards not only affects production operations but also forces businesses to spend extra time and money to troubleshoot, adjust the system, and maintain stable operations.
.jpg)
Ensuring wastewater quality meets standards before discharging into the environment.
Although oil and grease cause many operational impacts, most incidents can be mitigated if businesses establish good control right at the source and maintain appropriate operating regimes. Instead of only treating issues when the system encounters a problem, periodic monitoring and evaluation will help detect abnormal signs early, thereby reducing remediation costs and maintaining stable treatment efficiency.
To limit the impacts of oil and grease, businesses should prioritize control at the source rather than focusing solely on end-stage treatment. Maintaining the efficiency of grease traps or flotation systems will significantly reduce the load entering the biological facilities, thereby enhancing treatment efficiency and relieving pressure on the entire system.
Additionally, it is necessary to regularly monitor the influent oil and grease load, evaluate the efficiency of pretreatment facilities, check the quality of activated sludge, and periodically clean equipment prone to grease buildup. Synchronized monitoring of all stages will help businesses detect abnormal signs early before major incidents occur.
For each type of wastewater and plant scale, selecting the appropriate oil and grease separation technology also plays a vital role in maintaining long-term operational efficiency.
"In many cases, choosing the right oil and grease separation technology right at the source will significantly determine the operational efficiency of the entire wastewater treatment system. If businesses want to learn in detail about the operating principles, advantages, and application scope of each solution, they can refer to the article 'Excessive Oil and Grease in Wastewater – A Synthesis of the Most Effective Treatment Methods' to have a better basis for selecting suitable technology."
Oil and grease are not always the parameters with the highest values in seafood wastewater, but they are among the most common causes of operational incidents. If the oil and grease control stage operates ineffectively, a series of problems such as declining biological treatment efficiency, floating sludge, increased operating costs, and the risk of effluent failing to meet standards can all occur. Therefore, controlling oil and grease not only helps improve treatment efficiency but also contributes to protecting equipment lifespans, optimizing operating costs, and minimizing negative environmental impacts in the long run.
