The chemical composition and acute toxicity of whole digested municipal sewage sludges from twelve water pollution control plants were collected, fractionated, and analyzed. The chemical composition and acute toxicity of whole sewage sludges were compared with those of liquid sewage sludge phases. The chemical constituents analyzed included nutrients, conventional parameters, and U.S. Environmental Protection Agency consent decree priority pollutants. Results indicated that most toxic constituents were associated with suspended solids and were therefore dramatically reduced in the liquid phase sludge fractions. Despite the dramatic reduction of metals, pesticides, and other organic compounds in the liquid sludge phases, there was a distinct trend towards equivalent phase toxicity to Atlantic silversides (Menidia menidia) and grass shrimp (Palaemonetes pugio). However, whole sludges were generally more toxic to mysids (Mysidopsis bahia) than were the liquid phase sludges. Evidence to support the hypothesis that ammonia may be the major contributor to overall toxicity of the sewage sludges tested is presented and discussed.
A sewage sludge bioaccumulation potential test responsive to the U.S. Environmental Protection Agency's Ocean Dumping Regulations and Criteria was developed and evaluated with sludges from twelve water pollution control plants with secondary treatment. In keeping with the regulations, the test was designed to examine if hard clams, grass shrimp, and Atlantic silversides exposed to sludge exhibited statistically elevated body burdens of cadmium, mercury, PCB, DDT and metabolites, and petroleum hydrocarbons compared against controls. Exposure consisted of ten-day renewal followed by a two-day post-exposure period in clean seawater. Five replicate aquaria per treatment per species were employed using sludge concentrations of 0.033, 0.0084, and 0.0042%. Seven hundred and eighty tissue samples were analyzed for the specified chemicals. Of 195 possible statistical evaluations (13 sludges × 3 species × 5 chemicals), significant differences between treatment group means occurred in only 31 trials. However, in 27 of these trials, the highest body burden mean was (1) at or below pretest levels for the organisms tested, (2) within the concentration range exhibited by control groups over the study period, or (3) present in controls. The inherent limitations of basing pass/fail compliance of ocean-dumped material on a single timepoint exposure are discussed.
Characterization of the acute and chronic toxicity of effluent samples from the Patapsco Wastewater Treatment Plant (WWTP), Baltimore, Maryland, was performed approximately twice weekly from April 1986 to January 1987. Acute toxicity of both the primary and secondary effluents was evaluated using Ceriodaphnia dubia, Mysidopsis bahia, and Microtox [a luminescent marine bacteria Photobacterium phosphoreum (Beckman Instruments, Inc.)]; chronic toxicity was evaluated using the C. dubia seven-day chronic test. The data indicate that C. dubia was the most sensitive indicator of acute toxicity for both primary and secondary effluent wastewaters. The acute responses for M. bahia and Microtox were considerably less sensitive than those for C. dubia. The 48-h median lethal concentration (LC50) values for C. dubia ranged from 0.5 to 23.4% secondary effluent and 0.1 to 6.5% primary effluent wastewaters. Microtox 5-min median effective concentration (EC50) values ranged from 9.4 to 100% secondary effluent and 0.6 to 19.5% primary effluent, respectively. M. bahia 96-h LC50 values were 8.9 to 100% secondary effluent and 14.8 to 35.4% primary effluent, respectively. The seven-day C. dubia chronic values (ChV) for the primary and secondary effluents were only slightly lower than the acute responses, ranging from <0.1 to 9.4% secondary effluent and <0.1 to 6.5% primary effluent, respectively. As an additional characterization of the plant's treatment process effectiveness, influent and effluent samples were fractionated in an attempt to identify specific components of acute toxicity entering and leaving the WWTP. As a result of the fractionation study, nonpolar organic compounds appeared to be the major toxic component of the samples fractionated. While identification of the specific compounds causing toxicity in the nonpolar organic fractions was not possible, the octanol/water partition coefficient (Log P) values for the most toxic fractions were estimated to be approximately 6 to 9 in the summer samples and approximately 3.6 to 8.3 in the winter samples. Cations, anions, and polar organic compounds do not appear to be major contributors to the toxicity of the effluent samples fractionated. The percentage of toxicity reduction across the plant was approximately 50 to 90% for the three species tested.
The U.S. Ocean Dumping Regulations and Criteria (40 CFR 220-229) l i m i t t h e t y p e s , amount, and r e l e a s e r a t e s of waste into the marine environment. M a t e r i a l s t o be considered for ocean dumping must be assessed by a t e c h n i c a l e v a l u a t i o n of their potential environmental impact. Based on b i o a s s a y r e s u l t s , a limiting permissible concent r a t i o n (LPC) i s e s t a b l i s h e d t h a t s h a l l n o t b e exceeded beyond t h e
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