The treatment of high salinity wastewaters from small island communities by use of rotating biological contactors was evaluated. Domestic wastewaters containing up to full strength seawater were utilized. The effects of salinity, loading rate and disk media composition on organic removal rate were examined. It was shown that RBCs can treat high salinity wastewaters to the same degree as non-saline wastewaters. The resulting effluent organic content was adequate for discharge into either marine or freshwater receiving waters. Mean COD removals of 61% and 64% were achieved using hydraulic loading rates of 0.04 and 0.08 m³/m²⋅d (1.0 and 2.0 gpd/sq ft), respectively. At higher loading rates, up to 0.33 m³/m²⋅d (8.0 gpd/sq ft), organic removal efficiency was reduced. No difference in treatment efficiency was observed using either plastic or Masonite® as the disk media.
Applicability of four empirical phosphorus models to 22 western lakes is investigated. The models by Jones and Bachman, and Walker show significant agreement with observed phosphorus concentrations as indicated by the Spearman correlation of 0.809 and 0.812 respectively. The values calculated by the other two models by Dillon and Kirchner, show poor correlation with observed data. Vollenweider type classification charts are also derived for the four models. Although all the models show some degree of disagreement with the EPA National Eutrophication Survey trophic classifications, the models by Walker, and Jones and Bachman can be used for predicting a first cut estimate of total phosphorus for lakes low in nutrients.
Pilot studies with synthetic and actual dairy wastewater showed that anaerobic-filter pretreatment at ambient temperature (20-24°C) was capable of reducing total BOD5 by up to 96%. Analysis of the reactor kinetics showed that the reactions were complete in about two days detention time, which corresponded to a volumetric loading of 1.7 kg COD/m³-day. Because of declining marginal removals with increased detention time, simple kinetic expressions were not appropriate representations of the reactor performance. Fermentative reactions dominated during the first 0.75 days of treatment, while methanogenic reactions dominated thereafter. Although effluent quality deteriorated, the anaerobic filters could handle a severe shock load as long as sufficient alkalinity had been added to keep the pH above 6.8 throughout the reactor.
Two solids inventory control strategies for prevention of clarification failure in the activated sludge process are considered. Recycle rate control is shown to be effective for a certain class of operational situations. This control algorithm, however, is not applicable to situations in which an activated sludge system is experiencing severe hydraulic surges. In such situations clarification failure can be effectively controlled only through the application of the step-feed strategy in which the location of the feed to the aeration basin is shifted downstream in a multipass basin.
Combinations of storage and wet-weather treatment, integrated with dry-weather treatment facilities and nonstructural control measures on an area-wide basis, are found to provide the greatest and most cost-effective control of storm-water pollution. Case studies of three very promising, constructed and operating structural measures for controlling combined sewer overflow pollution demonstrate these concepts. Information on the design, operation, performance and costs of these facilities is provided and compared to guide future planners and designers. In Seattle, Washington, computerized control of in-line storage offers operational flexibility and inexpensive storage. At Saginaw, Michigan, off-line storage/treatment integrated with in-line storage and dry-weather treatment has achieved high performance at moderate costs. At Mount Clemens, Michigan, physical and biological wet-weather treatment processes promise very high treatment levels for combined sewage, if needed.
Lime addition to raw wastewater as an upgrading technique can significantly aid a rotating biological contactor (RBC) plant in producing effluents in compliance with federal discharge permit limitations for biochemical oxygen demand (BOD5), amonia nitrogen and phosphorus. Low-level lime addition does not require recarbonation and does not produce the sludges typical of high pH lime treatment schemes. The pilot RBC process provided BOD5 removal when subjected to an influent pH of 9.5 for hydraulic loading rates of 2.0, 3.0, and 4.0 gpd/sq ft (0.08, 0.12, and 0.6m³/m²⋅ day). In addition to the removal of phosphorus, lime pretreatment reduced the organic loading on the RBC process and allowed for recarbonation by microbial populations which produced carbon dioxide, thereby forming carbonate alkalinity necessity for nitrification after the initial BOD5 had been removed. The resultant pH after recarbonation was also in the optimal range for nitrification.
The acid rain model has been developed to simulate lake-watershed acidification processes. It provides a quantitative linkage between atmospheric deposition and lake water chemistry. The continuous simulation model is comprised of several modules including watershed hydrology, stream and lake hydraulics, canopy, snow, soil, stream and lake chemistry. The hydrology module simulates the processes of interception, throughfall, evapotranspiration, freezing and thawing of soil, and snow accumulation and melting. The model segregates the watershed horizontally into subcatchments and vertically into soil layers. Flows are routed through a layered soil profile to the streams and ultimately to the lake. Incoming precipitation and deep groundwater flow. Application of the model to Panther and Woods Lake basins in the Adirondack mountains of New York indicates the importance of flowpaths in determining lake water acidity.
A graphical solution is developed for determining sulfide buildup in gravity sanitary sewer pipe. The method utilizes the Pomeroy-Parkhurst equations for sulfide buildup first published in 1977. The Pomeroy-Parkhurst equations are based on studies conducted over the past 20 years in the Los Angeles Sanitation District's system. An extensive bibliography on sulfide generation, effects, and case histories is included.
Decentralization within metropolitan areas has been a major aspect of population movement in the United States over the past two decades. This trend has great significance for all urban service activities. In particular, it affects water supply planning in urban areas. Both numbers of people and their spatial location affect forecasting of water supply demands which, in turn, affect fixed plant investments (source works, treatment works, transmission lines, distribution systems, and so forth) which are frequently built many years in advance of the resulting services. This paper describes, via a case study, the use of population and per capita demands as a basis for forecasting water requirements. Water use is studied according to residential and nonresidential demand. These data, combined with extrapolated demand coefficients, can be used as the basis for demand forecasting that not only provides estimates of quantity of demand but location of demand as well.
The surface reaction model for the mechanism of mass transfer-metabolism in the fixed-film nitrification process is investigated and discussed for the design of trickling filter systems and rotating biological contactor (RBC) systems. Two experimental studies are performed. The first study, using a stationary fixed-film reactor to simulate the trickling filter process, reveals that the surface reaction kinetics follow a pseudo-homogeneous model. The second study, using a bench-scale RBC unit, indicates that the pseudo-homogeneous model is also applicable to the rotating fixed-film process. The effective slime thickness of an RBC system can be estimated from this model by locating the optimum NH3-N removal rotating speed and finding the corresponding liquid film thickness at that rotating speed.
In certain biofilm processes, such as nitrification and anaerobic carbon removal, biofilm attachment and growth may take several weeks or even months. This research focuses on determining the effect of synthetic and naturally produced polymers, used as surface conditioners, on the rate of biofilm attachment and growth. Partial success was obtained, and the only practical alternative seems to be to precondition the surface of the media by growing an easy-to-develop biological film before the final biofilm is induced to grow. This paper also reviews the literature which describes the factors affecting the attached growth of bacteria.
