A new sampler for stratified lagoon chemical and microbiological assessments

Authors: McLaughlin, Michael; Brooks, John; Adeli, Ardeshir

Submitted to: Environmental Monitoring and Assessment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2014
Publication Date: 6/1/2014
Citation: McLaughlin, M.R., Brooks, J.P., Adeli, A. 2014. A new sampler for stratified lagoon chemical and microbiological assessments. Environmental Monitoring and Assessment. 186:4097-4110.

Interpretive Summary: A new remotely controlled water column sampler was designed, constructed, and tested for use in a study of nutrient and bacterial stratification in a swine manure lagoon in the Mid-South US. The sampler was designed to collect multiple samples simultaneously from different depths in the water column. The new sampler was deployed and operated with minimal disturbance to the water column. The sampler displayed positional stability during sample collection and was easily recovered and reloaded with new sample bottles between sampling positions in the lagoon. The new sampler could be readily sanitized and transported between deployments. Water quality tests showed that pH, EC, nutrient concentrations, and bacterial levels did not differ significantly between samples collected at 0.04, 0.47, and 1.0 m depths, but differences between samples collected in winter and those collected in early spring were significant for five of ten nutrients and four of seven bacterial groups. Results demonstrated the utility of the new sampler in collection of samples from multiple depths, showed no stratification of nutrients or bacteria between 0.04 and 1.0 m depths, and suggested that a more extensive study of nutrients and bacteria could omit collections from 0.47 m, but should include a greater range of dates and seasons.

Technical Abstract: A water column sampler was needed to study stratification of nutrients and bacteria in a swine manure lagoon. Conventional samplers yielded shallow samples near the bank or required a boat. These limitations prompted development of a new sampler to collect at multiple depths with minimal disturbance to the water column. A portable floating sampler was designed around these requirements. The design used a tether for stability and remote control (RC) for sample collection. A modular sampling assembly design enabled quick replacement of sample tubing and containers between locations. The sampler comprised a PVC pontoon and Plexiglass deck with enclosures for a 12 V DC RC gearmotor to operate the collection module, and RC vacuum system to draw samples. Autoclavable tubing and 250-mL bottles were adapted with Luer fittings to collect samples. The sampler was tested in winter and spring by collecting at three depths and six locations in a 3.4 ha lagoon. The sampler was moved between locations on a custom-built PVC trailer. The sampling module created minimal disturbance in the water column, held a stable position during collection, and was easily replaced between locations. The sampler was rinsed with clean water and sanitizer and transported in a pickup. Analyses showed pH, EC, nutrient concentrations, and bacteria levels did not differ between 0.04, 0.47, and 1.0 m samples, but some nutrients and bacteria differed between winter and spring samples. Results demonstrated the utility of the sampler and suggested future studies include fewer or different depths and more sampling dates.