Brian J. Vinci

The cost and effectiveness of solids thickening technologies for treating backwash and recovering nutrients from intensive aquaculture systems

The cost and effectiveness of three solids thickening processes, i.e., gravity thickening settlers (GTS), inclined belt filters (IBF), geotextile bag filters (GBF), were individually evaluated with the biosolids backwash produced in intensive aquaculture systems equipped with microscreen drum filters and radial-flow settlers. The IBF produced the cleanest discharge and highest treatment efficiencies, likely reflecting the rapid efficiency with which solids are separated from wastewater. The GBF was the least effective process, i.e., GBF leachate contained the highest concentrations of TP, TN, and cBOD. However, GBF was most effective for sludge volume reduction. Capital cost estimates for an IBF were more than twice that of GTS and GBF of similar treatment capacity. The GTS had the lowest capital and annual operating cost estimates. The estimated annual operating cost of the GBF was orders of magnitude higher than the IBF and GTS, due to the high cost to replace bags.

Experimental evaluation of low head oxygenators

Abstract The overall mass transfer coefficient, G 20 , for a single hole orifice plate was evaluated in a series of experiments as affected by four geometric variables: orifice plate hole diameter (5, 10, 14, 19, and 22 mm), hydraulic head on the flooded plate (2.5, 5, and 13 cm), water fall height from the orifice to the receiving pool of water (30, 61, 91, and 122 cm), and the collection pool depth (2.5, 8, 13, 25, and 41 cm). This is, in essence, the simplest form of a low head oxygenator (LHO). A regression equation was developed to predict G 20 as a function of these variables, their interactions, and squared terms. The hydraulic head above the flooded plate had no significant effect ( P

Assessing the Suitability of a Partial Water Reuse System for Rearing Juvenile Chinook Salmon for Stocking in Washington State

To assess the suitability of water reuse technology for raising Pacific salmon Oncorhynchus spp. for stocking purposes, fish health and welfare were compared between two groups of juvenile Chinook salmon O. tshawytscha from the same spawn: one group was reared in a pilot partial water reuse system (circular tanks), and the other group was reared in a flow-through raceway. This observational study was carried out over a 21-week period in Washington State. Reuse and raceway fish were sampled repeatedly for pathogen screening and histopathology; fin erosion and whole-blood characteristics were also evaluated. By the studys end, no listed pathogens were isolated from either cohort, and survival was 99.3% and 99.0% in the reuse and raceway groups, respectively. Condition factor was 1.28 in raceway fish and 1.14 in reuse fish; this difference may have been attributable to occasional differences in feeding rates between the cohorts. Fin indices (i.e., length of the longest dorsal or caudal fin ray, standardized by fork length) were lower in reuse fish than in raceway fish, but fin erosion was not grossly apparent in either cohort. The most consistent histological lesion was gill epithelial hypertrophy in reuse fish; however, blood analyses did not suggest any corresponding physiological imbalances. Overall, results suggest that water reuse technology can be employed in rearing juvenile anadromous salmonids for stocking purposes.

A mathematical model of low-head oxygenators

A mathematical model is presented that predicts the performance of low-head oxygenators (LHO). Experimentally determined values of G20 for a single hole in a flooded orifice plate were used as the basis to develop a mathematical model that can be used to predict LHO performance under a variety of design and operating conditions. Model predictions were compared to two published studies. The model predicted the published data for dissolved oxygen levels in the departing effluent within 2–3%, oxygen absorption efficiencies within 5–6%, and total gas pressures within 1%. The mathematical model is thoroughly developed including an analysis of numerical stability and necessary restrictions to assure stability and accuracy. Convergence based solely upon effluent values was not sufficient to produce accurate results, but required additional criteria of requiring a minimum number of chamber flushings prior to convergence checking. The model was used to demonstrate its utility in predicting the effects of G/L ratio on gas absorption efficiency, effluent gas conditions and the effects of number of LHO chambers used. This model allows the designer or operator of an LHO to easily make design and operational decisions by modifying the input parameters and observing the exit conditions and performance indicators.

Characterizing bubble penetration from a falling stream

The depth that bubbles will penetrate a receiving pool before rising due to buoyancy forces is an important phenomena in designing Low Head Oxygenator (LHO) devices, particularly in an indoor application where the available elevation between the top of the fish tank water column and the inside ceiling height is limited. The relationship between bubble loss and LHO geometry is unclear. If the submergence of the LHO is less than the bubble penetration depth, excessive escape of bubbles can increase operating costs substantially. A series of physical experiments were conducted using an elevated bucket with a single orifice to create a falling stream into a receiving pool. The primary variables of hydraulic head, hole diameter and fall height were varied over a practical range for such applications. Videotaping was used to analyze bubble penetration. Regression equations were developed to predict both bubble penetration and standard deviation associated with a specific set of operating conditions. The standard deviation regression equation can be used to predict the statistical variation in bubble penetration depth. Bubble penetration depth decreased as fall height was increased and became stable at a fall height of 50 cm. Bubble penetration increased as hole diameter was increased at all fall heights and hydraulic heads. An example is provided of how to predict bubble penetration depth to meet some user defined statistical confidence for maximum bubble penetration.

Assessing the Utility of Ultraviolet Irradiation to Reduce Bacterial Biofilms in Fish Hatchery Well Water Supplies

The accumulation of bacterial biofilms and consequent clogging of screens, pipes, and heat exchanger equipment is problematic for water supply systems contaminated with iron bacteria and other slime forming bacteria. Despite the ubiquitous threat posed by iron bacteria contamination in groundwater sources, limited research has focused on physical treatments to address this issue. We sought to investigate the effectiveness of ultraviolet (UV) irradiation on inactivating iron bacteria and slime forming bacteria in a fish hatchery supply water known to have issues with bacterial biofilms. Biological activity reaction tests (BART) were used to analyze the presence or absence of iron related and slime forming bacteria in raw well water at UV dosages of 0 mJ/cm2, 15 mJ/cm2, 30 mJ/cm2, 45 mJ/cm2 and 60 mJ/cm2. Results suggest that UV treatment decreases iron bacteria survival, with the highest percent of non-reactive BARTTM test vials resulting from 45 mJ/cm2 and 60 mJ/cm2 UV exposure; however, data regarding UV inactivation of slime forming bacteria were inconclusive. These initial ‘proof of concept’ findings can be used to design pilot UV water treatment systems for fish hatcheries known to have iron bacteria problems. Pilot treatment system testing can then provide the necessary results to ensure that UV treatment is effective against site-specific iron bacteria populations before full-scale treatment systems are implemented.