Water Treatment for Fish Aquaculture System

Fish processing processes produce wastewater, that comprises active organic contaminating microbes in colloidal, soluble, and particle form, similar to other processing businesses. The degree of contaminants varies depending on the procedure. It might be light, moderate, or substantial.

Need of aquaculture water treatment

Varied fish species require a different set of water quality characteristics to survive, thrive, and reproduce, thus why aquaculture water treatment is important for sustainable fish farming. Each type does have its optimum range or the range where it works best, within certain tolerance limits. Thus, fish farmers must guarantee that the chemical and physical conditions of the water stay as close to ideal as feasible for the fish within their care at all times.

Fish will have poor growth, irregular behavior, illness symptoms, and parasite infestations if they are kept outside of these ideal parameters. Fish mortality may occur in extreme circumstances or when unfavorable conditions persist for an extended length of time.

Treatment stages for water for fish aquaculture system

The wastewater treatment process is divided into three stages: basic, intermediate, and tertiary water treatment. Further advanced treatment, termed as quaternary water treatment, is necessary in some applications.

Primary treatment

The term “primary treatment” refers to a collection of activities used to remove floatable and settling sediments. Due to secondary treatment, these solids are contained in an effluent, which uses biological and chemical processes to eliminate the majority of the residual organic matter. Only physical processes such as sedimentation, screening, and flotation are performed in the first treatment. The treatment used is mostly determined by the operations carried out from the fish processing plant as well as the wastewater disposal needs. Settling tanks or simple screening with small residence times could be employed where the only requirement is that no solids settle after 10 minutes. More complex methods, such as flotation and biological treatment, will be required as regulations get stricter.

Screening- In a primary treatment facility, relatively big solids (0.7 mm or larger) can be removed through screening. This is one of the most popular treatments employed by food processing companies since it minimizes the number of solids released quickly.

Sedimentation- Sedimentation is a technique for removing suspended particulates from wastewaters. Fish scales, parts of fish muscle, and offal are all found in fishery wastewaters, with the amounts variable depending on the method.

Oil and Grease separation- Gravity separation can be used to remove oil and grease if the oil particles are big enough to float to the surface and therefore are not emulsified.

Flotation- Flotation is a process that removes suspended particles as well as oil and grease.

Biological treatment

The purpose of all biological wastewater treatment systems is to use microbial populations to remove non-settling solids and dissolved organic load from effluents. Secondary treatment systems frequently include biological treatments. The microorganisms used in this process are responsible for the breakdown of organic matter as well as the stabilization of organic wastes. They can be classed as aerobic (need oxygen for metabolism), anaerobic or growth under a condition of lack of oxygen or facultative (grow in the presence of oxygen) Most microorganisms found in wastewater treatment systems develop by using the organic material of the wastewater as an energy source and are so nutritionally categorized as heterotrophs. A biological wastewater treatment population is diverse, complicated, and interconnected.

The different biological treatment procedures include:

Aerobic Processes

  • Aerated lagoons
  • Rotating biological contractors
  • Activated Sludge Systems
  • Aeration
  • Trickling filters
  • Choice of aerobic treatments

Anaerobic Treatment

  • Imhoff tanks
  • Digestion systems

Physicochemical treatments

Coagulation – Flocculation- A chemical substance is given to an organic colloidal suspension during coagulation operations to trigger its instability by reducing the forces that keep them apart. It entails lowering the surface charges that cause particle repulsion. Flocculation occurs as a result of the charge lowering (agglomeration). The bigger particles are then settled, and the effluent is clarified.


  • Chlorination- Chlorination is a frequent technique in both industrial and residential wastewaters.
  • Ozonation- Because of its bactericidal qualities and potential for viral elimination, ozone has been employed for disinfection because it is also a strong oxidizing agent. When a high voltage is discharged across a narrow gap in the presence of air or oxygen, ozone (O3) is created.


In aquaculture production systems, water quality is the most significant component impacting fish health and performance. The term “good water quality” relates to what the fish want, rather than what we assume they want. This necessitates a thorough understanding of the water quality requirements of the cultured fish. Fish are completely reliant on the water in which they reside for all of their needs