Inexpensive Apparatus to Rapidly Collect Water Samples from a Linear- Design, Plug-Flow Hatchery Raceway

摘要

In July 2001, we conducted a study to determine whether a target concentration of chloramine-T (a waterborne chemical) could be achieved and maintained for 60 min in linear-design, plug-flow hatchery raceways (devoid of fish) via a 'charged' flow-through treatment methodology. In each of four independent trials, a raceway was charged to achieve the target concentration by turning off the inflow water (creating a static bath) and manually mixing in a premeasured volume of chloramine-T stock solution. Water inflow was then turned on, and the target concentration was maintained by metering additional chloramine-T stock solution into the inflow water via a calibrated chicken- watering system. To help verify chloramine-T concentrations during treatment, we built an apparatus to rapidly collect many water samples from throughout a raceway. The apparatus comprised three fixed sampling stations, each of which was equipped with 9 water collection devices (i.e., nine 60-mL plastic syringes fitted with fixed-length 'suction needles' made of rigid polyvinyl chloride pipe threaded with flexible vinyl tubing) and 9-11 plastic bottles for storing the collected samples. During each of the four 60-min trials, water samples were collected at elapsed times of 0, 30, and 60 min; thus, 12 sampling events were conducted during the study. During each sampling event, three people (working simultaneously but independently) collected a total of 29 water samples (27 for chloramine-T dose verification and 2 for quality control). The time for one person to collect 9-11 water samples (50-60 mL per sample) from one sampling station averaged 1.5 min (SD = 0.382; n = 36) and ranged from 0.9 to 2.5 min. The apparatus was inexpensive, easy to build and use, and portable; it ultimately helped us verify the spatial and temporal distribution of chloramine-T in linear-design, plug-flow hatchery raceways during 60-min charged flow-through treatments.