News features and technical articles about the evolution of aquaculture, one of the world’s fastest growing industries.

Thomas M. Losordo

Innovation & Investment

Estimating biofilter size for RAS systems

Controlling total ammonia-nitrogen (TAN) concentrations is the primary concern when sizing a biofilter for use in a recirculating aquaculture system. Sizing decisions are best based on previous experience with a given biofilter media in a specific biofilter configuration. 

Innovation & Investment

Flow rate estimation for RAS

The water quality in recirculating aquaculture systems is generally a function of the tank size, biomass, feed inputs and waste treatment efficiency. Adequate biofiltration can control the build-up of ammonia-nitrogen and nitrate-nitrogen in the systems. 

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TAN, other water quality factors affect nitrification rates in biofilters

An important criterion when studying biofilters is the conversion rate of total ammonia nitrogen (TAN) to nitrate-nitrogen in production water. Although nitrification rates have been based on media surface areas, they do not always reflect the actual nitrification achieved. Volumetric 

Innovation & Investment

Recirculating aquaculture technology, part 2

To start a biofilter together with a source of nitrifying bacteria, you must provide the conditions that will encourage the growth of the bacteria. The basic process requires initial preparation of water chemistry, adjustment of alkalinity to support bacterial growth 

Innovation & Investment

Recirculating aquaculture technology, part 1

Biological filtration is one of the critical required unit processes in recirculating aquaculture systems. Non-corrosive filter media with large amounts of surface provides area for nitrifying bacteria cells to colonize. 


Geotextile bag, flocculant technology capture RAS waste

Geotextile bags used in combination with polymer flocculant aid chemicals can provide effective primary treatment of recirculating aquaculture system effluent. Much of the suspended solids that carry the majority of the organic load within the effluent can be captured by 

Innovation & Investment

Unit processes in RAS systems

For most effective use, water should have low turbidity and high U.V. transmittance, with ultraviolet dosage tuned to the target organisms. Low-pressure/high-output amalgam U.V. lamps are often used in RAS systems. 


A look at unit processes in RAS systems

The ability to maintain adequate oxygen levels can be a limiting factor in carrying capacities for RAS. The amount of oxygen required is largely dictated by the feed rate and length of time waste solids remain within the systems. 

Innovation & Investment

A review of unit processes in RAS systems

Since un-ionized ammonia-nitrogen and nitrite-nitrogen are toxic to most finfish, controlling their concentrations in culture tanks is a primary objective in the design of recirculating aquaculture systems.