Journal of Environmental Engineering

Disinfection with chlorine dioxide was compared to disinfection with chlorine in wastewater from three treatment sequences: (1) Conventional activated‐sludge treatment; (2) activated‐sludge/nitrification; and (3) activated‐sludge/nitrification/filtration treatment. The comparisons were made based on correlations of fractional survival of coliform bacteria with the product of residual concentration times contact time for each disinfectant. Laboratory experiments were conducted in a complete randomized block design, with mass dose of disinfectant (3 levels) and contact time (3 levels) as independent variables. The laboratory experiments were conducted in a four‐liter batch reactor. In general, both chlorine and chlorine dioxide give decreased survival ratios for increases in dose or contact time. In all cases, chlorine dioxide achieved a given fractional kill with an equal or lower residual time product than chlorine. Chlorine dioxide demand is greater in conventional secondary effluent than the chlorine demand, but less than that for chlorine in nitrified effluents. The chloramines found in non‐nitrified wastewaters are much less effective in disinfection than “free” chlorine. The disinfection effectiveness of chlorine dioxide, and to a lesser extent that of chlorine, is enhanced by the filtration process in both conventional secondary effluent and in nitrified effluent.

The design of natural attenuation type sanitary landfills receiving municipal refuse is controlled by some key parameters in leachate. The attenuation mechanism(s) of the key parameters in the leachate are included. Equation to calculate average concentration of a pollutant due to dilution in a groundwater has been developed. A semi‐quantitative design method for municipal landfills has been suggested. It is concluded that heavy metals in leachate from a municipal landfill sited on a clayey stratum overlying a sandy aquifer will be highly attenuated but concentration of BOD, chloride, COD, hardness and iron in the groundwater will increase.

Methodology derived from sampling theory is presented for the estimation of in‐stream contaminant mass‐discharge or load. The historical record is stratified into relatively homogeneous units in order to approach normality in the subpopulations thereby reducing the inaccuracies introduced by the highly skewed populations. Within strata a ratio estimator is employed to estimate the load and variance of the subpopulations. Strata are also defined to minimize other forms of inaccuracy. Estimates for individual strata are combined to produce pooled estimates for the desired period of interest. With a prior data base, sampling theory is employed to devise sampling strategies designed to produce load estimates of a specified target precision in future studies. Case studies demonstrate the significance of flow events as the primary transport mechanism for suspended sediment and the need to sample such events intensively in order to achieve reliable load estimates. Small “flashy” streams require sampling of much greater intensity during events than larger rivers with attenuated event response in order to produce load estimates of comparable precision.

Two models were calibrated to the 1978 primary productivity conditions of nutrient‐rich hypereutrophic Onondaga Lake, N.Y.; one was based on the approach of Bannister, the other on a more conventional format. The data base, necessary for model development, included continuously monitored incident photosynthetically active radiation (PAR), and 115 parallel measurements of water column temperature, PAR attenuation, chlorophyll a, primary productivity, and key nutrients. Values of key parameters for the Bannister model, obtained by evaluation of the data set, differed from those recommended in the literature. Both models effectively predicted seasonal and shortterm trends in primary productivity for most of the study, though the Bannister model was slightly better. The Bannister model predictions were particularly sensitive to estimates of the maximum quantum yield of photosynthesis. The Bannister model is preferred on theoretical grounds, since it incorporates more fundamental and more constant parameters, and more properly accounts for temperature influences.

This case study presents the methodology for collecting and interpreting the data for assessing the correlations among variables (required pumping frequency, user satisfaction, management district preference, user knowledge, and unit type). The chi‐square distribution technique is employed to evaluate the significance of correlations. This technique unveils the reasons why the homeowners are satisfied with their units and prefer a specific approach for operating and maintaining their units. This study also provides information about management functions performed by the typical county institutions, type and estimated number of on‐site systems in use and failing, causes of system failures, and approaches for mitigating failing systems. The methodology developed for conducting the investigation and for interpreting the data can be used in any other region, and the result provides valuable information to practicing engineers in conducting facility planning for rural communities.

Two models describing the sorption of hydrophobic organic pollutants are compared. The models describe interactions in the water column between the fraction adsorbed on suspended sediments and the fraction in solution. They differ in that one considers desorption kinetics while the other assumes the adsorbed and dissolved fractions are always in equilibrium. The study shows that as the time constant of the system expressing the relative importance of sorption and elimination rate increases, the results of the models converge to the same value. The octanol‐water partition coefficient has a strong and positive correlation with this ratio. This means that for organic compounds with a high octanol‐water partition coefficient, equilibrium models will probably be more accurate than for compounds with a low octanol‐water partition coefficient. Relationships are developed whereby a modeler may determine if the kinetic approach is necessary or if the equilibrium approach is satisfactory.

Low rate biological treatment processes such as aerated lagoons, oxidation ditches, etc. offer several advantages over high rate processes, especially at small communities and industrial plants. However, in order to satisfy mixing requirements in low rate treatment processes a substantial amount of energy must be provided. The energy consumption can be significantly reduced by the use of mobile, and, in particular, self‐propelled aerators. Self‐propelled aerators differ from stationary aerators in two major respects. First, their movement upon the water surface in treatment installations or natural water bodies causes the involvement of considerably larger volumes of water in the mixing process and second, they provide more uniform suspension of microorganisms in the water being aerated. At the same time, the driving force causing the aerators to move upon the water surface is induced by the aeration device itself. This eliminates the need for special propelling devices and thus permits a simple design of the aeration device. In this study, parameters for self‐propelled mechanical and jet aerators are analyzed and several possible applications are discussed. The major parameters for self‐propelled aerators are the linear velocity of movement upon the water surface, the period of rotation, the service area, and the oxygenation capacity. Possible applications of self‐propelled jet aerators are illustrated by means of examples.

A comprehensive water quality management plan was prepared for the Laguna de Bay Basin located near Metropolitan Manila, Philippines. The need for this management plan has been created by the confrontation between resources development and environmental conservation and made complex by the spill‐over of Metro‐Manila population, industrial and commercial growths and agricultural development in the watershed of this large inland tropical lake. A water quality management plan was prepared by Government with the cooperation of international agencies to protect the natural resources so that the beneficial uses of the lake can be preserved. The initial phases of the comprehensive water quality management plan are under implementation.

Water filtration plants used to remove asbestos fibers should be designed to produce filtered water with very low turbidity (0.10 ntu or lower). A key design factor in accomplishing this is to provide for flexibility in plant operation, especially with respect to conditioning raw water for filtration. The preconditioning and the filtration should be viewed as interdependent portions of the clarification process, which should be designed to operate at maximum efficiency. Water quality monitoring is very important. Adequate monitoring capability must be provided. Careful control of pH is necessary during coagulation, and filtered water turbidity should be monitored continuously so filters can be backwashed before large amounts of floe and asbestos fibers are discharged from the filter into the treated water. Pilot plant studies as well as design and operation of full scale plants show that producing low turbidity water is attainable for Lake Superior and Cascade Mountain waters. Design data and treatment results are also presented.

Tetrazolium reduction assays, based on the reduction of 2‐(p‐iodophenyl)‐3‐(p‐nitrophenyl)‐5‐phenyl tetrazolium chloride (INT) to INT‐formazan by active bacterial electron transport systems, were used to differentiate between the physiological activities of filamentous and floc‐forming microorganisms in activated sludge following applications of chlorine. With proper dosage of chlorine, filaments (predominantly Sphaerotilus natans) were almost completely inactivated while floc‐forming microorganisms were only partially inhibited. Trends in the specific activity of S. atans anticipated similar trends in sludge volume index. Tetrazolium reduction assays were used in conjunction with a short term, static biassay to predict the chlorine dosage which controlled Sphaerotilus bulking in a bench scale, activated sludge system.

A ground‐water modeling study was conducted at the Love Canal area, Niagara Falls, New York, as part of a comprehensive evaluation of contamination at the area. The hydrogeology underlying Love Canal consists of a shallow system of silts and fine sands, underlain by confining layers of lacustrine clays and glacial till, which are underlain by the Lockport Dolomite. A two‐dimensional computer model of the Lockport Dolomite was constructed to help define the ground‐water flow system. Both history matching and a sensitivity analysis were conducted. Assuming the dolomite was contaminated, Monte Carlo simulation and uncertainty analysis were used to estimate contaminant travel times to the upper Niagara River. Results indicate that travel times would average 1,000 days with less than 5% probability of less than 100 days or greater than 10,000 days. Analysis of remedial action for the Lockport Dolomite using best estimates of hydrologic parameters indicates that three interceptor wells at the south end of the canal, pumped at only $1\text{,}155{\mathrm{ft}}^3/\mathrm{day}$ $(32.3m^3/\mathrm{day})\text{,}$ should reverse the flow of ground water to the river and provide an adequate barrier to migration of potential contaminants to the river.

An evaluation, conducted by model simulation, is presented of the impacts the elimination of chemically-based physical stratification and the range of behavior of phytoplankton released from hypereutrophic Onondaga Lake would have on the dissolved oxygen resources of the Seneca River, under critical flow, temperature, and loading conditions. Further, a method is presented for determining the minimum fraction of lake phytoplankton that will decay in a receiving river under conditions of nutrient saturation for both systems. The elimination of physical stratification in the river was predicted to cause degradation of oxygen conditions in the surface waters of the river; ranging from noncontravention to severe contravention of present standards (daily average concentration of 5.0 mgl⁻¹). This broad range of potential impact is associated with the degree of uncertainty in behavior of lake phytoplankton in the river.

The use of Rhodamine WT fluorescent dye in the presence of nitrite was recently linked with the formation of diethylnitrosamine (DENA), a compound with mutagenic and carcinogenic properties. Lissamine FF fluorescent dye was selected as a substitute for Rhodamine WT dye to avoid potential problems upstream of water intakes. In a series of comparative tests with Rhodamine WT dye, Lissamine FF dye was found to have a higher minimum detectability limit, to be less temperature dependent, to be highly sensitive to chlorine content, to be less soluble, and more expensive than Rhodamine WT.

The Manchester, New Hampshire water treatment plant employs granular activated carbon and full conventional treatment. An 18 month sampling program to determine the effect of GAC upon finished water microbial quality was conducted. The GAC bed itself promoted the regrowth of standard plate count organisms, but had no effect on coliforms, endotoxins, or acidfast organisms. This regrowth did not occur in a rapid sand filter immediately upstream of the GAC contactor. The regrowth of organisms within the GAC bed could be correlated with temperature, and chlorine residual. Following terminal chlorination, the increased microbial levels were reduced and no problems attributable to GAC were noted in the subsequent distribution system.

This paper presents a mathematical model describing the process of vacuum deodorization of digested sludge odorants. This model is based on a mass balance of odorant substance drawn around the vacuum chamber, assuming first order decay rate of odorant substance in the deodorization process. The developed model enables one to determine the rate constant, odor removal potentiality, and process time requirement for achieving a desired off-gas odor concentration. The validity of the model has been tested with the data obtained from a pilot operation of vacuum deodorization of sludge odorants. The practical significance of this model is that it can be used to predict the process time requirement for achieving a desired off-gas odor concentration.