COMPARATIVE EFFECTS OF HALOGENATED HYDROCARBON
SOLVENTS ON WASTE DISPOSAL PROCESSES
Eugenia N. Benson, Research Intern
Joseph V. Hunter, Professor
Department of Environmental Science
Rutgers University
New Brunswick, New Jersey 08903
INTRODUCTION
Substantial use of halogenated hydrocarbon solvents in numerous industries and laboratories raises the issue of the effect these have on the environment [ 1 ], and specifically on
sewage treatment processes [2].   In this study, three such solvents, 1,1, 1-trichloroethane,
l,l,2-trichloro-l,2,2-trifluoroethane, and tetrachloroethylene were investigated.   Their
toxicity on batch-type anaerobic digesters was studied, since anaerobic digestion has been
reported more susceptible to inhibition than other sewage treatment processes [1,3,4].  A
threshold effect concentration of each was found, and an attempt was made to determine
the fate of each halocarbon during digestion.
In addition to the anaerobic digestion studies, the distribution of tetrachloroethylene
between settled sewage and sludge of raw, primary influent was investigated.   Such data
should prove of practical value in predicting final solvent concentrations in sludge and
facilitate prevention of digestion failure.
Anaerobic digestion failures caused by halogenated hydrocarbons have been reported
in England [4-6,8,9].   These episodes prompted laboratory investigations into the effect
of such solvents.   A summary of the relative toxicities of 10 such compounds has been
prepared from reports in the literature [2,3,7,9-15], and is shown in Figure 1.   The variations in experimental procedures and criteria of inhibition do not make quotations of
toxic concentrations in Figure 1 reliable.   Our studies were conducted under conditions
that were internally consistent, thus allowing comparison of the effect of the halogenated
hydrocarbon solvents tested.
MATERIALS AND METHODS
Analytical Procedures
All halocarbon solvent analyses were conducted on an A.I.D. Portable Gas Chromato-
graph   Model 510, equipped with an electron capture detector (H3 source) and an Ester-
line Angus Model T171B-2 Port-a-graph recorder.   Later in the study a Spectra-Physics
Autolab Minigrator electronic integrator was obtained to facilitate peak area measurements.
The column used was 8 ft by 1/8 in. i.d. stainless steel, packed with 10% SP 2100 on
80/100 mesh Supelcoport.   The carrier gas was 95% Argon-5% Methane, purified by a
molecular sieve trap.   The inlet and detector temperature and gas flow rate for trichloro-
ethane and trichlorotrifluoroethane were 50 C and 19 ml/min, and for tetrachloroethylene
100 C and 15 ml/min.   Peak areas were determined by measuring triangle areas, by weighing
or by the electronic integrator.
Digester gas was sampled directly.   Sewage or sludge was initially extracted with pesticide
quality hexane, and the hexane solution, dried with Na2S04, was injected into the gas
chromatograph.   Determination of actual concentrations was conducted by correcting all
values with a correction factor (obtained by adding known concentrations to sewage and
measuring recoveries).
614
-