63    CHARACTERIZATION AND TREATMENT OF
WASTEWATER GENERATED FROM SALINE
AQUACULTURE OF CHANNEL CATFISH
Ricardo B. Jacquez, Associate Professor
Paul R. Turner, Assistant Professor
Hamdy El-Reyes, Graduate Research Assistant
(iiih-Ming Lou, Graduate Research Assistant
Department of Civil Engineering
New Mexico State University
Las Cruces, New Mexico 88003
INTRODUCTION
Background
The Southwest desert of the United States is characterized by arid climate and limited availability of
freshwater. Because of this freshwater limitation, aquaculture, which is very water intensive, has not
developed into a prominent industry in New Mexico. However, production of aquatic animals could
be accomplished economically using intensive recirculating systems and brackish groundwaters. Total
New Mexico groundwater reserves (fresh and brackish) have been estimated at 2.5 x 1013 m3 of which
75% is brackish ( 1000 mg/L total dissolved solids (TDS)) [1]. Brackish groundwaters in New Mexico
contain up to 200,000 mg/L TDS but most of the supply is much less than 100,000 mg/L [2]. Such is
the case in Roswell, New Mexico where the groundwater has a TDS concentration of 14,000 mg/L.
The water is not usable for direct human consumption or conventional agriculture without extensive
dilution or desalination but has the potential to be used for culturing salt tolerant fish species. Some
species of fish grow well in brackish water while other species such as channel catfish could be
cultured only in freshwater or in slightly brackish water (10,000 mg/L TDS) [3,4].
Research Objectives
The specific objectives outlined for the study were as follows:
1. Determine the pollution load generated by an intensive catfish culture system operating
at a salinity range between 1000 to 9000 mg/L TDS.
2. Evaluate the effect of high salinity on biological nitrification in submerged filters.
Scope of Study
The first phase of the study was conducted at the Roswell Test Facility (RTF) located in Roswell,
New Mexico. Fingerling channel catfish (Ictalurus punctatus) were grown in circular raceways containing brackish groundwater ranging in salinity between 1000 to 9000 mg/L TDS. The catfish growth
studies were conducted over a six month period. Water samples to characterize the pollutional load
generated by the catfish were collected and analyzed during the last three months of the study.
The second phase of the study was conducted in the laboratory of the Civil Engineering Department
at New Mexico State University (NMSU). The effect of high salinity on biological nitrification was
evaluated by operating five, laboratory scale, submerged, nitrification filters using brackish groundwater from the RTF. The five salinity levels which were evaluated included TDS concentrations
ranging from 1000 to 9000 mg/L. In addition to the filter studies, respirometer studies were performed to determine the influence of high salinity on the exertion of nitrogenous biochemical oxygen
demand.
530