Benthic Community Structure and Surfactants in the Trinity River

The Trinity River in North Central Texas flows through the Dallas-Ft. Worth (DFW) metroplex area and is typical of many urban rivers in the Southwestern United States that have flows dominated by input from wastewater treatment plants (WWTPs). The domination of Trinity River flow by discharges from DFW WWTPs presents an opportunity to examine the environmental behavior of down-the-drain household chemicals in a major river system that represents near-worse case conditions. The Soap and Detergent Association (SDA) “Surfactants in Sediments Task Force” sponsored the current study in collaboration with the University of North Texas (UNT) Institute of Applied Sciences and EA Engineering, Science, and
Technology, Inc., to examine potential ecological effects of surfactants in the Trinity River in the DFW metroplex area by looking at sources of surfactants, fate, and possible indicators of effects due to surfactants in environmental media. A workshop and a series of conference calls between SDA, UNT, and EA, produced a study design that examined the Dallas-Ft. Worth area as a single, internally variable source of surfactants to the Trinity River. The study looked at
reference sites upstream of Dallas WWTP inputs, WWTP effluent and mixing zone sites within the metroplex, and downstream sites where inputs and concentrations were expected to decrease.

Occurrence and weight-of-evidence risk assessment of alkyl sulfates, alkyl ethoxysulfates, and linear alkyl benzene sulfonates (LAS) in river water and sedimnets

Alkyl sulfates (AS), alkyl ethoxysulfates (AES) and linear alkyl benzene sulfonates (LAS) are all High Production Volume (HPV) and ‘down-the-drain’ chemicals used globally in detergent and personal care products, resulting in low levels ultimately released to the environment via wastewater effluent. Due to their surfactant properties, they preferentially sorb to sediments. Hence, assessment of their levels and potential perturbations on benthos are of interest. The relative levels of AS/AES decreased with distance from the wastewater treatment plant outfall. However, this was not evident for LAS. Short chained AES and especially AS dominated the homologue distribution for AES. There were no evident patterns in LAS homologue distribution. The overall mean margin of exposure (MoE) for AS/AES and LAS is not, vert, similar 40 (range: 3 to 100) suggesting no noteworthy perturbation on biota. The findings in this study are in concordance with previous preliminary hazard screening. Comparative sediment contamination analyses principally based on Chapman and Anderson [Chapman PM, Anderson, J. A decision-making framework for sediment contamination. Integr Environ Assess Mana. 2005; 1: 163–173.] and the U.S. Environmental Protection Agency RAPID assessment methods [USEPA. Rapid bioassessment protocols for use in wadeable streams and rivers: Periphyton, benthic, macroinvertebrates, and fish. 1999. Second Edition. U.S. Environmental Protection Agency Office of Water, Washington, D.C. EPA 841-B-99-002.] did not reveal significant correlations between the surfactant concentrations and ecological status of the sampling locations. Several Lines of Evidence (LoE) of the Weight-of-Evidence (WoE) lead to the conclusion of low aquatic risk associated to the monitored compounds.

Assessing the Impact of Household Cleaning Products on Wastewater Treatment Systems

The concern has been expressed that disposal of unused household cleaning products can disrupt microbial wastewater treatment processes. This paper reviews the techniques used to evaluate the toxicity of cleaning products to residential wastewater treatment processes and examines examples of available data concerning common products under the most probable worst-case cenario—single-residence septic tanks. Microbial toxicity tests most commonly examine consumption of oxygen by microorganisms, production of anaerobic gases, or removal of a reference compound. If the concentration of the test substance is maintained below the “no-observed effect concentration” (NOEC) in these conservative tests, it is presumed that no toxicity will occur in the wastewater treatment process. The four case studies reviewed support the conclusion that disposal of whole-package quantities of typical household cleaning products results in little or no observed effect on septic tank function.

The Effect of Sediment Organic Carbon on the Toxicity of a Surfactant to Hyalella Azteca

In this study, effects of organic carbon on anionic surfactant toxicity were determined using highly branched alkylbenzene sulfonate as the test compound in order to limit losses from biodegradation.

Relationships between benthic macroinvertebrate community structure and geospatial habitat, in-stream water chemistry, and surfactants in the effluent-dominated Trinity River, Texas, USA

Benthic macroinvertebrate community structure has been studied in the upper Trinity River (Texas, USA) over the past 20 years. The Trinity River represents an effluent-dominated, near-worst-case scenario to examine the environmental effects of domestic–municipal and industrial effluents on aquatic life. A study from the late 1980's concluded that many stretches of the river supported a diverse benthic community structure; however, a decline in taxa richness occurred immediately downstream of WWTPs. A 2005 study designed to parallel the previous efforts evaluated how changes in water quality, habitat, and increased urbanization impacted benthic community structure. The results are described in this publication. Environmental Toxicology and Chemistry, 30:1127–1138.