Assessment of water quality and benthic macroinvertebrate community in a wastewater receiving constructed wetland

Jennifer Lynn Martinez, University of Texas at El Paso


In the El Paso region around the 1930s there was a loss of riparian areas and wetlands due to canalization of the Rio Grande. In an attempt to bring back native flora and fauna that once flourished in the floodplain of the Rio Grande region, the creation of Rio Bosque Wetlands Park (RBWP; El Paso Co., TX) was initiated in 1995. As part of the construction agreement, El Paso Water Utilities agreed to provide water to fill the wetland upon its completion. Beginning in 1998, RBWP was filled with treated effluent from the adjacent Roberto Bustamante Wastewater Treatment Plant (WWTP) during the non-irrigation season. Using treated wastewater to fill Rio Bosque's wetland cells is of concern due to contaminants and their metabolites that may remain after treatment. This study assesses the water quality of RBWP by specifically examining pollutants that are known to impact water quality: nutrients and other water chemistry parameters, heavy metals and arsenic, and PPCPs. Further investigations included determining benthic macroinvertebrate (BMI) communities in selected sites within RBWP, and the acute effects of selected pharmaceuticals and personal care products ( the stimulant, caffeine; the antibiotic, erythromycin; the analgesic/anti-pyretic, acetaminophen; and the plastics/epoxy resin, BPA) to non-biting midges (Diptera: Chironomidae). During the course of this study nutrients (ammonia, nitrite + nitrate, phosphate, and chlorophyll-a) exceeded the state water quality criteria. Major factors driving macroinvertebrate community composition may be high levels of nutrients and hydroperiod. Most heavy metals analyzed were below consensus sediment quality guidelines. However, Cd levels exceeded threshold effect concentration (TEC; below which harmful effects are unlikely to be observed) levels, suggesting that this metal may have harmful effects to BMI community composition at RBWP. Of the 9 pharmaceuticals analyzed, ciprofloxacin and codeine were detected in highest concentrations in water and sediment samples. Two additional compounds: caffeine and trimethoprim were detected frequently in sediment samples. Since the concentrations of all compounds were low (ng/L), they do not seem to pose a great risk according to the findings from the 48 hr toxicity tests conducted here as well as other published studies. Supporting the contention that acute toxic effects of many PPCPs are unlikely; however, chronic environmental toxicity cannot be excluded. During the course of this study, nearly 31,000 benthic macroinvertebrates were collected. Out of the seventeen different taxa that were identified, two groups: midge larvae (Diptera: Chironomidae), and nematodes (Nematoda) were two dominant taxa that accounted for over 50% of the total benthic macroinvertebrates collected on most occasions. This type of community composition is expected because these taxonomic groups represent fauna that are tolerant to poor water quality, which enables them to inhabit the aquatic environment and sediments associated with the study sites at RBWP, an effluent receiving wetland. Water availability is likely the major factor that determines the BMI community that is able to colonize RBWP.

Subject Area

Ecology|Water Resource Management|Environmental science

Recommended Citation

Martinez, Jennifer Lynn, "Assessment of water quality and benthic macroinvertebrate community in a wastewater receiving constructed wetland" (2013). ETD Collection for University of Texas, El Paso. AAI1552267.