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.     

Microbiological characterization of the biological treatment of aircraft paint stripping wastewater

Leaching rates of the herbicide dichlorprop [(+/--2-(2,4-dichlorophenoxy)propanoic acid] and nitrate were measured together in field lysimeters containing undisturbed clay and peat soils. The purpose of the study was to investigate the leaching pattern of the two solutes in structured soils under different precipitation regimes. Spring barley (Hordeum distichum L.) was sown on each monolith and fertilized with 100 kg N ha(-1). Dichlorprop was applied at a rate of 1.6 kg active ingredient (a.i.) ha(-1). Each soil type received supplemental irrigation at two levels ('average' and 'worst-case'), giving total water inputs (irrigation and precipitation) of 664 and 749 mm year(-1), respectively. The larger water input approximately doubled the nitrate loads, from, on average, 11.6 to 21.8 kg N ha(-1) year(-1) in the clay soil and from 37.6 to 65.4 kg N ha(-1) year(-1) in the peat soil. In contrast, dichlorprop leaching was reduced by more than one order of magnitude when the water input was increased, from average amounts of 3.22 to 0.26 g a.i. ha(-1) during an S-month period in the clay and from 28.9 to 2.67 g a.i. ha(-1) in the peat. This leaching pattern of dichlorprop was explained in terms of preferential flow. The dried-out topsoil of 'average' watered monoliths may have allowed water flow in cracks, thus moving some of the herbicide rapidly through the topsoil to the subsoil. Once the compound reached the subsoil, degradation rates would be reduced and the herbicide residues would be stored for later leaching. Nitrate was presumably more evenly distributed in the soil matrix; therefore, water rapidly moving through macropores would not carry significant amounts of nitrate. In contrast, leaching would occur more evenly through the soil matrix, causing larger nitrate loads in the 'worst-case' watered monoliths. These results show that wet years may constitute a worst case scenario in terms of nitrate leaching, but not pesticide leaching, if macropore flow exerts a significant influence on leaching.     

Geographic information systems: a tool for strategic ground water quality management

Geographically‐related information is needed for several elements of an integrated ground water quality management programme, including ground water monitoring planning, prioritization of pollution sources, usage of permits and inspections for source control, and planning and completion of remedial actions. Geographic Information Systems (GISs) can be used to support these elements along with delineating wellhead protection areas (WHPAs), prioritizing existing contaminant sources and evaluating proposed changes in land usage in such areas. Eight case studies of the use of GISs in wellhead protection programmes are summarized, including examples from Rhode Island, Mississippi, New Jersey, New York, Pennsylvania, Kansas, Massachusetts and Texas. Six additional examples are mentioned relative to the use of GISs for evaluating ground water pollution potential, facilitating data analysis for environmental restoration of a large area with numerous waste sites, evaluating trends in ground water nitrate contamination, establishing a national database for ground water vulnerability to agricultural chemicals, simulating water table altitudes from stream and drainage basin locations, and selecting radioactive waste dump sites. The applicability of GISs and their associated advantages in wellhead protection and other ground water management studies are demonstrated via the case studies. The GIS technology provides a unique opportunity for analysing and visualizing spatial data. Contaminant and source prioritization within WHPAs is needed for both extant conditions and in the evaluation of proposed land use changes. The coupling of a GIS with contaminant/source prioritization would provide a strategic tool which could be used to plan targeted ground water monitoring programmes, to identify appropriate management or mitigation measures, minimize introduction of contaminants from existing sources into the subsurface environment, and to evaluate the potential of proposed land use activities for causing ground water contamination. GISs can be useful in providing current information for policy makers, planners and managers engaged in ground water quality decision making.