This report consists of three phases. Phase one was a review of existing information on all aspects of recreational vehicle (RV) wastewater additives. Surveys and interviews were held with retailers selling RV wastewater holding tank additives, RV owners and RV users. The surveys and interviews revealed that formaldehyde-methanol additives were the most widely used followed by paraformaldehyde formulations.
The second phase explored the toxicity of commercially available additives when used in a dosage recommended by the manufacture. The Microtox [superscript] R toxicity bioassay and the change in oxygen uptake by sewage degrading microorganisms were used as indicators of toxicity. Formaldehyde-methanol formulation showed the greatest immediate toxicity. This was followed in decreasing toxicity by the alkyl phenoxy polyethoxy ethanol, paraformaldehyde, quaternary ammonium chloride, and enzyme-detergent formations. Enzymes which contained an inert filler were found to be non-toxic. The adverse impact of the additive on the oxygen uptake rate showed that the formaldehyde-methanol had a biocidal effect while enzyme formulations had no effect. The other additives caused a slow down in the rate of oxygen uptake by the microorganisms.
The final phase of the study characterized the RV wastewater being dumped at the rest stations and the characteristics of various wastewater streams in the biological treatment systems. The three parameters monitored were the 5-day Biochemical oxygen demand (5-day BOD), pH and Microtox toxicity.