Microbiological characterization of the biological treatment of aircraft paint stripping wastewater.

Research on the treatment of potentially toxic wastewater produced at six US Navy aircraft paint stripping facilities has been conducted. The composition of the wastewater treated consisted of methylene chloride and phenol in concentrations of about 5000 and 1800 mg/l, respectively, and other organic compounds in a total concentration of 2200 mg/l. Biological treatment is an important means by which toxic or hazardous organic compounds can be economically converted to less noxious materials. Engineering studies conducted in the laboratory with activated sludge reactors and rotating biological contactors (RBC) demonstrated that both suspended and attached growths can be effective biological methods to treat this paint stripping wastewater when blended with domestic wastewater up to about 50% by volume. These studies were complemented with analyses of the bacterial communities inhabiting the treatment systems. The number and the genera of the microorganisms present in the blended wastewater, as well as their ability to biodegrade the potentially toxic organics were studied. The results indicate that paint stripping wastewater is able to support large bacterial populations consisting of various gram-negative rods and coccibacilli and a few gram-positive bacilli. Members of the genera Pseudomonas and Bacillus are suspected to play an important role in initiating the biodegradation process.

Microbiology of high-sodium-nitrite-wastewater treatment.

A microbiological study conducted as a complement to kinetic studies of biological denitrification as a process for treating high-sodium-nitrite wastewaters generated from ship-boiler-tube cleaning is described. The number, genera, and denitrifying capabilities of the organisms inhabiting anoxic suspended-growth reactors used in the kinetic studies were evaluated for four experimental phases. The results regarding the enumeration of bacteria supported the findings of the kinetic studies as follows: (i) the better nitrite-removal efficiencies observed in the nitrification/denitrification system as compared with direct denitrification were confirmed by the presence of larger populations of organisms capable of completely reducing nitrate or nitrite; (ii) the presence of metals in concentrations associated with boiler-tube wastewater did not affect removal performance in the nitrification/denitrification systems, nor did it affect the density of complete denitrifiers; (iii) increasing sludge ages resulted in increasing nitrite-removal efficiencies as well as populations of complete denitrifiers; and (iv) a decrease in nitrate-removal efficiencies when the actual wastewater was introduced to a system that had been acclimated to the synthetic wastewater coincided with a reduction in the number of complete denitrifiers. Regarding the types of organisms found in this study, denitrifying strains of Alcaligenes and Pseudomonas were always present in the anoxic reactors along with other denitrifying and non-denitrifying bacteria of the same genera, or other genera such as Acinetobacter and Flavobacterium. However, members of the genus Alcaligenes were the only complete denitrifiers found in the anoxic reactors, and hence they are likely to play a key role in the denitrification process.

Biological nitrification/denitrification of high sodium nitrite (navy shipyard) wastewater.

In the hydroblasting of ships' boiler tubes, a wastewater high in nitrite (as high as 1200 mg litre(-1)) is produced by the US Navy. This research has evaluated the use of a suspended-growth biological system to treat this wastewater by denitrification. Two biological treatment configurations were evaluated (direct denitrification versus nitrification/denitrification) with nitrification/denitrification producing better nitrite removal efficiencies (54 to 62% versus 40%, respectively). The introduction of metals (cadmium, chromium, lead, copper and iron) in concentrations typical for this wastewater did not inhibit the nitrite removal efficiencies. The influent metal concentrations ranged from 0.02 mg litre(-1) for cadmium to 22 mg litre(-1) for iron and the metal removal efficiencies ranged from 4.8% for cadmium to 50% for copper. Increasing sludge age resulted in improved nitrite removal efficiencies (52%, 57% and 74% for sludge ages of 4, 6 and 8 days, respectively). The resulting biokinetic constants were similar to those reported by others for lower influent concentrations of nitrite or nitrate (Ygs=0.02 mg/mg; Ygn=0.16 mg/mg; Yb=0.8 mg/mg; and b=0.006 h(-1)).

Effect of long-term low and moderate levels of carbon monoxide exposure on platelet counts of rabbits.

Most of the traditional studies of carbon monoxide (CO) toxicology have emphasized the dramatic effects of heavy exposure, therefore, remarkably little information is available about the consequences occurring after exposure to low concentrations similar to those found in the polluted community air. In previous studies hypoxia has been reported to cause a decrease in platelet counts in experimental animals. In an effort to investigate the abnormalities of circulating platelets in rabbits exposed to low and moderate levels of CO, three groups of animals were studied. The first (control) group of rabbits breathed ambient air whereas the second was exposed to low level CO (50 ppm by volume) for 24 hr continuously for 8 weeks. The third group was exposed to 300 ppm for 4 weeks (8 hr/day for 5 days). Per cent oxyhemoglobin (HbO2), per cent hemoglobin (Hb) and per cent carboxyhemoglobin (HbCO) and circulating platelet counts were monitored in all groups. A consistant pattern of change in circulating platelet quantity was found at the observed time intervals in CO exposed animals. No changes were observed in the same tests in rabbits exposed to ambient air. Prolonged low level CO exposure may influence change in circulating platelet counts and/or congenital platelet function disorders in man through this mechanism.

Enhancement of fibrinolysis in rabbits exposed to low and moderate levels of carbon monoxide inhibited by epsilon amino caproic acid.

The first (control) group of rabbits breathed ambient air whereas the second was exposed to low level carbon monoxide (CO, 50 ppm by volume) for 24 hr continuously for 8 weeks. The third group was exposed to 300 ppm CO for 4 weeks. The fourth group was exposed to 300 ppm CO for the same period of time as the third group but in addition they were also given epsilon amino caproic acid (EACA) orally, and the results compared to Group III. Per cent oxyhemoglobin (HbO2), per cent hemoglobin (Hb) and per cent carboxyhemoglobin (HbCO) were monitored in all groups. Tests of fibrinolysis were monitored and showed acceleration of the whole blood clot lysis and euglobulin lysis times (ELT). A fibrin plate test confirmed the increased lysis and serum fibrin and/or fibrinogen degradation products (FDP) were elevated in the CO exposed animals. No changes were observed in the same tests in the rabbits exposed to ambient air. The fourth group of animals receiving EACA showed inhibition of lysis and decrease in serum FDP. Alpha-1-antitrypsin and alpha-2-macroglobulin assays in all groups showed no change. Microscopic examination of the large vessels in these test groups showed endothelial damage which indicates a possible source for a plasminogen activator release, or lead to action of Hageman factor and activated plasma plasminogen proactivator.