Aquaculture Sludge treatment

Customized turnkey solutions for aquaculture effluent and sludge treatment

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Aquaculture sludge treatment systems designed for easy installation and the ability to turn sludge into a valuable resource.

Alumichem product range offers customized turnkey solutions for treatment of effluents and sludge from aquaculture regardless of species.

Our solutions have the following advantages:

Meeting your stringent discharge requirements

The requirements for wastewater treatment and discharge are becoming stricter – both in Europe and globally.

By partnering with Alumichem, you are guaranteed the system solutions comply with your current environmental legislations and you will receive peace of mind that they can be adapted for any future requirements

Solutions for RAS intake and effluent treatment

Customized turnkey solutions to treat intake water and effluents from Recirculating Aquaculture Systems (RAS).

1. Water intake filtration

Alumichem supplies solutions for membrane ultrafiltration
of your intake water to ensure safe fish farm operation. This
will be designed according to your needs ensuring protection against harmful substances like bacteria, vira, heavy
metals etc. Read more about intake water treatment –>

2. Sludge thickening

The initial sludge thickening step takes the dry matter content from 0-1% and up to 10% solids and significantly reduces the sludge amount

The process consists of two parts:

  • Chemical conditioning of the sludge to build large flocs
  • Mechanical filtration to separate these floc particles from water

After thickening, the sludge is ideal for biogas production

3. Sludge dewatering

The thickened sludge can be further dewatered in a dewatering step, in which the dry matter content can reach 30% solids and the sludge amount is further reduced for easy transportation.

After the sludge dewatering step, the sludge is ideal as fertilizer in local agriculture or as carbon source in a composting facility.

4. Sludge drying

The dewatered sludge can be further treated in a sludge dryer. In this step the dry matter content can reach >90% solids and the dried sludge is hygienized for easy and safe handling and storage, e.g., in bigbags

Alumichem uses very energy efficient heat pump dryers. The dried sludge contains high value nutrients and energy, which can be utilized in production of fertilizer or thermal energy.

5. Polishing of discharge water

The reject water from the sludge treatment steps and any overflow water from the RAS plant is polished before discharge/reuse to ensure compliance with any environmental regulation

The water can be treated for any remaining solids, nitrogen, phosphorous, TOC, heavy metals etc.

A selection of our effluent treatment partners:

Customized solutions for sludge treatment

Alumichem offers various customized solutions for aquaculture sludge treatment. Our solutions are designed, engineered, and combined according to any given customer requirement. Let us help you maximize performance and minimize risk by supporting you before, during, and after start-up.

Our services 

Contact our expert
Trevor Gent

Effluent treatment for Norwegian Salmon producer

Case study: Alumichem’s customized solution for aquaculture effluent treatment helped a Norwegian Salmon producer to comply with strict discharge limits.   A Norwegian salmon producer was expanding their RAS (Recirculating Aquaculture System) facility but was concerned about their new stricter effluent discharge limits and what to do with their increasing sludge amounts.



Turning sludge into a valuable resource

Sludge from aquaculture is a potential fertilizer, however it cannot be used directly as fertilizer due to the content of heavy metals and chemical polymers and is generally regarded as a waste product.

Alumichem offers unique sludge treatment solutions without the use of chemical polymers, by removing heavy metals and without creating hazardous by-products turning sludge into a valuable resource.

Alumichem Sludge system has been successfully installed at fish farms where it effectively removes the contaminants from the waste stream, producing clean, recyclable water and a contaminant-free sludge which can then be further processed to form a dry material that is easy to handle and store, allowing the owners to turn contaminated fish sludge into a usable fertilizer, and so turning an expensive waste product into a valuable commodity.

Treatment process

The typical process utilizes polymer to flocculate the sludge and make dewatering possible. The flocculated sludge is separated in a filtration or sedimentation process, before being further dewatered and dried.

Read more about our custom solutions and technologies for water treatment

The solutions listed below are not standard solutions, but examples of some of the different possibilities we offer.

Flocculants – gravity belt filter – decanter

It is essential to use a flocculant on gravity belt. The flocculant will accelerate the drainage of water and allow it to flow through the sludge and the filtration belt. The flocculated sludge flows over a filtration belt that is conveyed at a certain speed.

The water freed by the flocculation step is drained through the pores of the belt. This elimination of water leads to a thickening of the sludge at the end of the conveyer belt. Nozzle sprays cleans the pore of the belt to prevent plugging.

The filtrate is returned to the beginning of the process while the thickened sludge is sent to a temporary storage tank before it is pumped to the decanter for further dewatering.

Flocculants – Drum dewatering unit

The principle is identical to the gravity belt. Sludge conditioning with a flocculant, liberation of interstitial water in the sludge, gravity drainage of the free water through a grid of the drum dewater unit. A drum dewatering unit is preferred when the requirement to the dry matter content is higher than the belt filter.

Electrolysis – ultrasound – separator – decanter – drying

The flocculation process of the sludge is a combined process of electrolysis and power ultrasound. The flocculated sludge flows to the separator, which removes the flocs, before the dewatered sludge is pumped into the decanter. From the decanter the semi-dried sludge is let through a drying unit as final stage of the sludge treatment.

Explore the Processes we work with in Aquaculture sludge treatment

Sludge treatment

Alumichem supply sludge treatment chemicals and equipment and the expertise to optimize the sludge...

Heavy metal removal

Products and solutions for removal of all types of heavy metals from wastewater...


Complete range of coagulants. we are experts in optimising coagulation processes in the treatment...

Polymer / flocculation

We have unique and vast experience in the supply and use of polymers, which benefits our customers in particular.