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The effect of phase separation on anaerobic biodegradation was evaluated in terms of thermodynamic principles. Individual components of common wastewaters were considered, and results indicate that the response of different substrates to phase-separated anaerobic treatment is diverse. A key element is the response of soluble substrates to acidification when syntrophic relationships are eliminated and biological reactions that require syntrophic relationships are altered. The acidification of carbohydrates and some proteins is thermodynamically favorable. In contrast, the acidification of fatty acids and aromatics is not thermodynamically favorable unless a sink for reducing equivalents is available. Reported data are consistent with this analysis and phase separation has been observed to enhance the treatment of carbohydrate wastewaters. In addition, the potential for detoxification of specific inhibitory compounds under acidifying conditions has been observed. Whether or not treatment of certain substrates will be enhanced by phase separation should be considered in the choice of reactor design, recognizing that various reactor designs exhibit different degrees of phase separation. This paper presents an overview on how phase-separated treatment affects the biodegradation of specific substrates and relates this to the selection of reactor designs. Water Environ. Res., 66, 716 (1994).

This study investigated the occurrence of pharmaceuticals, emphasizing triiodinated benzene derivatives used as X-ray contrast media, in domestic effluents and their fate during subsequent groundwater recharge. Organic iodine measurements were used as a surrogate for triiodinated benzene derivatives. Seven wastewater treatment facilities in Texas, Arizona and California were studied and organic iodine concentrations at these facilities varied between 5 and 40 microg iodine/L. The highest concentrations were observed on weekdays reflecting the common practice of employing X-ray examinations between Monday and Friday. Organic iodine compounds in secondary treated effluents were not removed by advanced wastewater treatment using ozone. However, organic iodine was efficiently removed by reverse osmosis membrane treatment. Based on laboratory biodegradation experiments and field studies negligible removal occurred under aerobic redox conditions while anoxic conditions led to partial removal of organic iodine. However, a concentration range of 8-15 microg iodine/L was observed in groundwater recharge systems after travel times of 8 to 10 years. Beside appropriate redox conditions, bioavailable organic carbon seems to be a key factor for organic iodine biodegradation in the environment. No environmental risk is expected from the parent compounds of triiodinated contrast media, however, toxicological effects associated with the metabolites are unknown.

The scope of this study was to investigate how natural organic matter (NOM) from drinking water and soluble microbial products (SMP) generated in the wastewater treatment process influence the character of DOC in reclaimed water used for indirect potable reuse. Biodegradation studies in conjunction with XAD-fractionation and 13C-NMR spectroscopy were applied to both characterize organic matter and to study removal mechanisms during subsequent soil-aquifer treatment (SAT). Based on hydraulically corresponding samples of drinking water and reclaimed water from reuse sites in Arizona and California, residual DOC in reclaimed water after SAT was dominated in concentration and character by NOM. Changes in DOC character were observed with increasing retention times during SAT in the direction to more aliphatic and less aromatic compounds indicative of humification with biodegradation as the dominant transformation process for bulk organics.

Water quality transformations during soil aquifer treatment at the Mesa Northwest Water Reclamation Plant (NWWRP) were evaluated by sampling a network of groundwater monitoring wells located within the reclaimed water plume. The Mesa Northwest Water Reclamation Plant has used soil aquifer treatment (SAT) since it began operation in 1990 and the recovery of reclaimed water from the impacted groundwater has been minimal. Groundwater samples obtained represent travel times from several days to greater than five years. Samples were analyzed for a wide range of organic and inorganic constituents. Sulfate was used as a tracer to estimate travel times and define reclaimed water plume movement. Dissolved organic carbon concentrations were reduced to approximately 1 mg/L after 12 to 24 months of soil aquifer treatment with an applied DOC concentration from the NWWRP of 5 to 7 mg/L. The specific ultraviolet absorbance (SUVA) increased during initial soil aquifer treatment on a time-scale of days and then decreased as longer term soil aquifer treatment removed UV absorbing compounds. The trihalomethane formation potential (THMFP) was a function of the dissolved organic carbon concentration and ranged from 50 to 65 micrograms THMFP/mg DOC. Analysis of trace organics revealed that the majority of trace organics were removed as DOC was removed with the exception of organic iodine. The majority of nitrogen was applied as nitrate-nitrogen and the reclaimed water plume had lower nitrate-nitrogen concentrations as compared to the background groundwater. The average dissolved organic carbon concentrations in the reclaimed water plume were less than 50% of the drinking water dissolved organic concentrations from which the reclaimed water originated.