Mariculture Systems Research Articles

PRELIMINARY STUDIES ON A COMBINED SEAWEED MARICULTURE‐TERTIARY WASTE TREATMENT SYSTEM1

ABSTRACTA pilot‐plant scale waste recycling‐mariculture system was developed at the Woods Hole Oceanographic Institution's Environmental Systems Laboratory in 1973. Basically, the concept of this system is to grow unicellular marine algae in continuous flow cultures on mixtures of seawater and secondarily treated sewage effluent, and feed the algae to bivalve molluses, maintained in a separate culture system. A final polishing step in the system consists of macroscopic algae (seaweeds) which remove the dissolved nutrients regenerated by the animal culture prior to discharge of the final effluent. In addition to serving as a final polishing step in the phytoplankton‐shellfish waste recycling system, seaweeds are also used as a one‐step waste recycling‐mariculture system.Currently, in the seweed systems, red alage are being grown which contain either agar or carrageenam both of which are in short supply and therefore have a high economic value. Yields from these seaweed mariculture systems are notably high compared to other maricultural and agricultural crops. Results indicate that seaweed farms will be an ecomomically profitable enterprise especially for developing countries in warm climates.

Fresh water, energy, and food from the sea and the sun

Surface waters of tropic and sub-tropic seas hold most of the solar energy retained by the earth; but the heat therein may be increased even more by heat which can be added by intensive solar heaters. The sea water so heated naturally or additionally by the sun, when flash evaporated, gives vapors which may be passed through a heat engine to give power, then condensed at a lower pressure to give fresh water, which may be much more valuable than the power produced. Heat of condensation is removed by circulating cold sea water from a depth of a few thousand feet. This water from the deep also has considerable nutrients for sea plants and animals coming from the degradation of former sea life; and these nutrients may be used in well studied mariculture systems to grow commercial food fish in ponds adjacent the land-based plant. Various arrangements of flows of the several liquid streams are presented to illustrate variations to the process which will produce fresh water and/or electric power, also food fish. These modifications may be optimized with various component systems, some of which are well known and evaluated in this usage, including the use of a second thermodynamic fluid, conventional multistage flash evaporation, also two of its variations: Controlled Flash Evaporation and Vapor Reheat. Calculations indicate that even without the use of intensive solar heaters, a profitable desalination and mariculture operation may be expected which would pay for its substantial cost in two or three years of profits; however, the incorporation of certain intensive solar heaters may increase the profitability significantly.

A Modular Nitrification Filter Design Based on a Study of the Kinetics of Nitrification of Marine Bacteria

ABSTRACTThe scope and significance of the problem of maintaining the quality of the water in recirculating mariculture systems is discussed. A quantitative study of the kinetics of important nutrient cycles is proposed as a means of establishing minimum system volumes, optimization of design, and the requisite environmental controls. Significant results in a study of inorganic nutrient nitrogen cycling and toxicity in recirculating systems is reported. A modular filter design suggested by a study of the kinetics of nitrification in marine systems demonstrates how a knowledge of kinetic and chemical factors can lead to more efficient water treatment hardware.