Abstract  In the past five years the U. S. Environmental Protection Agency has studied the effectiveness of steam stripping as a treatment technique for removing organics from aqueous waste streams. This paper presents the data obtained from field tests of steam strippers at seven industrial facilities. The effectiveness of steam striping for removing different types of organics from wastewaters is discussed.

Abstract  Biodegradation of dichloromethane (DCM) to environmentally acceptable products was demonstrated under methanogenic conditions (35 degrees C). When DCM was supplied to enrichment cultures as the sole organic compound at a low enough concentration to avoid inhibition of methanogenesis, the molar ratio of CH4 formed to DCM consumed (0.473) was very close to the amount predicted by stoichiometric conservation of electrons. DCM degradation was also demonstrated when methanogenesis was partially inhibited (with 0.5 to 1.5 mM 2-bromoethanesulfonate or approximately 2 mM DCM) or completely stopped (with 50 to 55.5 mM 2-bromoethanesulfonate). Addition of a eubacterial inhibitor (vancomycin, 100 mg/liter) greatly reduced the rate of DCM degradation. 14CO2 was the principal product of [14C]DCM degradation, followed by 14CH4 (when methanogenesis was uninhibited) or 14CH3COOH (when methanogenesis was partially or completely inhibited). Hydrogen accumulated during DCM degradation and then returned to background levels when DCM was consumed. These results suggested that nonmethanogenic organisms mediated DCM degradation, oxidizing a portion to CO2 and fermenting the remainder to acetate; acetate formation suggested involvement of an acetogen. Methanogens in the enrichment culture then converted the products of DCM degradation to CH4. Aceticlastic methanogens were more easily inhibited by 2-bromoethanesulfonate and DCM than were CO2-reducing methanogens. When DCM was the sole organic-carbon and electron donor source supplied, its use as a growth substrate was demonstrated. The highest observed yield was 0.085 g of suspended organic carbon formed per g of DCM carbon consumed. Approximately 85% of the biomass formed was attributable to the growth of nonmethanogens, and 15% was attributable to methanogens.

Abstract  This research investigated the potential for anaerobic, biological degradation of five chlorinated C1 and C2 hydrocarbons: tetrachloroethylene (PCE), trichloroethylene (TCE), 1,1,1-trichloroethane (1,1,1-TCA), chloroform (CF), and dichloromethane (DCM). Attempts were made to delineate the importance of microbial -- as opposed to purely chemical -- mechanisms of degradation; products formed; and pathways involved. The five compounds were studied separately in batch, anaerobic systems employing a diverse community of microflora from a municipal waste treatment plant. The added substrate concentrations ranged from 2-25 mg/L for the C1 compounds, and from 1-2 mg/L for the C2 compounds. Radiotracer studies were conducted with 14C-chloroform and 14C-dichloromethane to investigate their fate, as well as to delineate degradative pathways. PCE was completely converted to TCE, but the product was not further degraded to any significant degree. Results suggest that the microbially mediated reductive dechlorination of PCE is an inducible process. Anaerobic conversion of 1,1,1-trichloroethane did not require acclimation. Anaerobic, microbial utilization of chloroform (CF) proceeded without acclimation. Microbial degradation of DCM occurred readily after an acclimation period of variable length. CF inhibits utilization of DCM in a manner that is slowly reversible. Inhibition persists long after levels of CF in the solution are depleted.

Abstract  HEEP COPYRIGHT: BIOL ABS. The basic microbial responses to benzene, toluene, phenol, nitrobenzene, methylene chloride o-dichlorobenezene, 2,4-dinitrotoluene and 2,6-dinitrotoluene were investigated. The microbial population of the industrial wastewater treatment units used in this study was comprised of 4 bacterial genera (Acinetobacter, Alcaligenes Flavobacterium and Pseudomonas) and 1 yeast (Rhodotorula). The toxicity levels, degradation rate and loss by volatilization of the organic compounds were determined, and metabolic by-products formed from the parent compounds were identified. Knowledge of the metabolic by-products of these organics may provide useful information on the complex nature of ring compound degradation. The possibility that breakdown of the studies organic compounds could result in the formation of other toxic materials was discussed.

Abstract  Nineteen compounds listed in the category of priority substances (PS) were selected for a biodegradation study using standardized tests. The compounds consist of pesticides, chlorinated solvents and volatile organic compounds (VOCs). In this paper, the choice of the most suitable method is discussed in relation to the physico-chemical properties of each substance. Zahn–Wellens, manometric respirometry and closed-bottle tests are alternatively used. Experimental results are presented and interpreted. Toxicity (Microtox™) and bacterial viability (Bac-light™) are also used as tools to investigate the influence of each substance on the microbial population (activated sludge). In addition, experimental values are compared with predictive data calculated according to quantitative structure activity relationships (QSARs) models. Biodeg Models were permitted to correctly estimate 17 substances; Survey Models and screening tests also revealed the same behavior for 16 target compounds.

Abstract  Dichloromethane (DCM) is utilized by the strictly anaerobic, acetogenic mixed culture DM as a sole source of carbon and energy for growth. Growth with DCM was linear, and cell suspensions of the culture degraded DCM with a specific activity of 0.47 mkat/kg of protein. A mass balance of 2 mol of chloride and 0.42 mol of acetate per mol of DCM was observed. The dehalogenation reaction showed similar specific activities under both anaerobic and aerobic conditions. Radioactivity from [14C]DCM in cell suspensions was recovered largely as 14CO2 (58%), [14C]acetate (23%), and [14C]formate (11%), which subsequently disappeared. This suggested that formate is a major intermediate in the pathway from DCM to acetate. Efforts to isolate from culture DM a pure culture capable of anaerobic growth with DCM were unsuccessful, although overall acetogenesis and the partial reactions are thermodynamically favorable. We then isolated bacterial strains DMA, a strictly anaerobic, gram-positive, endospore-forming rod, and DMB, a strictly anaerobic, gram-negative, endospore-forming homoacetogen, from culture DM. Both strain DMB and Methanospirillum hungatei utilized formate as a source of carbon and energy. Coculture of strain DMA with either M. hungatei or strain DMB in solid medium with DCM as the sole added source of carbon and energy was observed. These data support a tentative scheme for the acetogenic fermentation of DCM involving interspecies formate transfer from strain DMA to the acetogenic bacterium DMB or to the methanogen M. hungatei.

Abstract  Sorption of toxic organic compounds on primary, mixed-liquor, and digested solids from municipal wastewater treatment plants has been correlated with octanol/water partition coefficients and with modified Randic indexes. It has been shown that the correlations are the same for all three types of wastewater solids used in this study if partition coefficients are calculated on the basis of organic content of the solids. The correlations developed are useful for assessing the role of sorption in the treatment of toxic or hazardous compounds in conventional biological wastewater treatment plants. Correlations developed provide a basis for predicting the concentration of toxic compounds associated with wastewater solids at a given equilibrium concentration in the aqueous phase. Organic compounds in sludge can impact anaerobic digestion, land spreading, incineration, and ocean dumping of sludges. Estimates of the concentration of toxic compounds in sludge allow assessment of the impact of toxic compounds on sludge disposal options.