Design, Construction, and Performance Evaluation of an Ozonation Pilot Plant

The treatment of water and wastewater may involve numerous chemical and physical unit processes. Each unit process is selected on the basis of its ability to accomplish specified treatment objectives. Ozone treatment is one such chemical unit process alternative. Ozonation is commonly practices abroad. Presently, nearly one thousand water treatment facilities in Western Europe use ozone for various applications. Ozone treatment of water is not common in the United States with just five installations as 1979. However, rising costs of chemicals, recent advances in ozone technology, and new treatment regulations and discharge requirements have enhanced the use of ozone as a water and wastewater treatment alternative. The theory of the reactions of ozone for treatment of water and wastewater is well recorded. However, due to the site-specific nature of the ozonation process, it is difficult to predict he practical or economic feasibility of ozone treatment without supporting data. These data may be best obtained by conducting ozonation experiments at the prospective site on a pilot-plant scale. The objectives of this research were: (1) To design, specify, and direct the construction of a portable ozonation pilot plant suitable for water and wastewater treat feasibility studies. (2) To evaluate the performance of the ozonation pilot plant under field conditions. The contents of this paper include a review of the factors related to the design and construction of a pilot plant ozonation system. The components of the pilot plant are also described. Finally, the results of a performance evaluation of the pilot plant are discussed

The role of suspension characteristics in continuous gravity thickening

Sludges resulting from water and wastewater treatment processes consist of agglomerated individual particles producing aggregates of various sizes and densities. Particle size, particle density, aggregate size and aggregate density are characteristics which determine the amenability of a suspension to continuous gravity thickening. To investigate the effects of these suspension characteristics on compression zone behavior, precipitation softening water treatment sludges and diatomaceous earth suspensions were gravity thickened in a pilot-scale continuous thickener. The effects of raking on thickening performance in the compression zone and the effects of suspension characteristics on channeling were also investigated;The behavior of the sludges in the compression zone of the continuous thickener was characterized using sludge concentration profiles and permeability and compressibility relationships. Suspension aggregate size and density were evaluated using a velocity-voidage correlation for hindered settling of the suspensions;When judged on the basis of the sludge concentration profiles and resulting underflow concentrations from the continuous thickener, the thickening performance of the sludges examined in this investigation was significantly affected by the sludge aggregate characteristics. Correlations between aggregate characteristics and permeability and compressibility explained the differences in thickening behavior;The occurrence of channeling in the compression zone was a function of aggregate characteristics for the diatomaceous earth suspensions, whereas compression zone channeling occurred for all softening sludges examined in this investigation, regardless of aggregate properties;Raking the compression zone obliterated channeling, causing poorer thickening performance of those suspensions which channeled in the compression zone

Effects of Storage Tank Mixing on Water Quality

Storage tanks are used by water systems to maintain pressure in the distribution system and to meet the varying water demands of the system. The design and operation of the storage tanks affect their mixing characteristics which affect the water quality. Poor mixing can lead to stratification in the tanks, which can lead to low chlorine residual causing microbial growth and nitrification. This thesis presents the results of the study of seven storage tanks used in South Dakota’s rural water systems. The tanks were chosen to represent varying height to diameter ratios, varying types of disinfectant, and to study passive mixing systems. The study used temperature data from all of the tanks and water quality data from five of the tanks. Temperature and water sampling apparatus were installed into each of the five tanks to examine the tanks’ behavior at varying heights. Hydraulic parameters including volumetric exchange, densimetric Froude number, and the dimensionless mixing parameter (Roberts et al. 2006) were examined to determine if they could predict the tanks’ mixing capabilities by comparing the actual values with theoretical values required for mixing the tank. Chlorine decay modeling was completed using the CompTank program. The model results were compared with actual data obtained during the study to determine the models capability to predict chlorine decay. The data showed that thermal stratification occurred in a few of the tanks resulting in water quality stratification and depleted chlorine residual in the upper zone of the tanks. High height-to-diameter storage tanks were more susceptible to stratification. To remediate stratification in one tank, the water system drained a large portion of the tank volume into its distribution system and refilled the tank with fresh water. A second system with a stratified tank chose to overflow the storage tank. Both methods were successful in restoring the chlorine residual. Passive mixing systems were installed in two tanks to prevent stratification. As a result of the passive mixing systems, both tanks were properly mixed, indicating that passive mixing systems can be effective in mixing storage tanks. Chorine residual measurements in two tanks throughout the study were used to develop chlorine decay coefficients used for the CompTank model. When the resulting decay coefficients were inserted into the model, the model substantially fit the chlorine decay that occurred in the upper zone of the stratified tanks

The Effects of Tank Operation and Design Characteristics on Water Quality in Distribution System Storage Tanks

From the Executive Summary Background: Regional water systems utilize storage facilities to meet demand variations and pressure requirements of their systems. These storage facilities drain and fill in response to system water demands and water level control settings. Storage tanks are typically placed in strategic locations to maintain a consistent pressure in the distribution system. Storage facilities should be designed and operated such that the water is mixed to prevent stagnant water (old water that remains in the tank for an extended period). Stagnant water can lead to water quality issues, such as low disinfectant residuals, potential for microbial contamination, disinfectant by-product formation, and nitrification in chloraminated waters. Many tanks have been built without consideration of mixing. These tanks might have a single inlet/outlet, high height to diameter ratio, or have other design characteristics that do not promote mixing. Whether by design or not, tanks without artificial mixing depend upon movement of water during the filling process to mix the tank. A wide array of storage tank types and geometries are utilized in South Dakota’s regional rural water systems. Greater understanding of the relationships of these tank characteristics on stored water quality would enable water systems to optimize the design and operation of their tanks. Objective of Study:The objective of this study was to examine the impacts of tank design and operation on mixing and water quality in storage tanks in South Dakota’s regional rural water systems. This objective was met through a literature review, a survey of system characteristics and evaluation of water quality data obtained from several storage tanks

Social/Physical Impacts and Water Consumption Characteristics of South Dakota’s Rural Water Systems

This study investigates the social and physical impacts that rural water systems have on South Dakota’s population and the water consumption characteristics of city, country dwelling, and farm customer classifications. The physical characteristics of South Dakota’s rural water systems along with the 2006 water production and sales information were used to determine and relate the unique distribution characteristics and water consumption demands of the rural water systems. The impact of improved water quality to the customers of the rural water systems was shown in improved livestock production and health, customer softening salt savings, and reduction of total dissolved solids entering South Dakota’s water ways. To examine the unique distribution system characteristics and water consumption demands of regional rural water systems, the water consumption characteristics and trends of city, country dwelling, and farm customers of Big Sioux Community Water System, Clay Rural Water System, Mid-Dakota Rural Water, and TM Rural Water District were compared. The results indicated that South Dakota’s regional rural water systems generally average 1.5 water meters per square mile. As a result of lower water hardness distributed through rural water systems, customers that switch from a community water system to rural water and use an ion exchange system in their dwelling could annually save $31.91 per year due to lower salt use for regeneration. The lower regeneration frequency improved water quality by reduced dissolved solids discharged into the water environment by 800 pounds per year. Farmers that switched their water source from private wells to rural water experienced increased livestock production and health - one dairy farm located in the TM Rural Water District saw a daily milk yield increase of 8 to 10 pounds per cow. Water use records of customers served by rural water system indicated cities with populations fewer than 100 used 71 gallons per person per person per day, customers of cities with populations ranging from 100 to 500 used 87 gallons per person per day, and customers in cities with populations over 500 used 119 gallons per person per day. The daily water demand for country dwelling customers ranged from 151 gallons per day to 335 gallons per day, and generally experienced an increase in customer numbers from 1999 to 2007. Farm customers had the highest averaged daily water demand at 456 gallons per day

Economic Impact of South Dakota’s Regional Water Systems

Regional water systems are a primary conduit of water supply for much of South Dakota’s rural and small community populations. As of 2006, greater than one-third of South Dakota’s population was served by water supplied from regional water systems, and when Lewis and Clark Rural Water delivers water to Sioux Falls, over one-half of South Dakota’s population will be served by regional water systems. Greater than 75% of incorporated communities with public water supplies are served by regional water systems, either as bulk communities or as individual customers. Many farms and agricultural industries use rural water for domestic use, livestock watering, and industrial processing. These users have connected to regional water systems to obtain a reliable, safe, and high quality water source. This report summarizes the results of a study of the economic impacts of regional water systems in South Dakota. The scope of this study was limited to soliciting financial information from South Dakota’s regional rural water systems using this information to quantify direct, indirect, and induced economic impacts of these systems as a result of their construction and annual operations

The role of suspension characteristics in continuous gravity thickening

Sludges resulting from water and wastewater treatment processes consist of agglomerated individual particles producing aggregates of various sizes and densities. Particle size, particle density, aggregate size and aggregate density are characteristics which determine the amenability of a suspension to continuous gravity thickening. To investigate the effects of these suspension characteristics on compression zone behavior, precipitation softening water treatment sludges and diatomaceous earth suspensions were gravity thickened in a pilot-scale continuous thickener. The effects of raking on thickening performance in the compression zone and the effects of suspension characteristics on channeling were also investigated;The behavior of the sludges in the compression zone of the continuous thickener was characterized using sludge concentration profiles and permeability and compressibility relationships. Suspension aggregate size and density were evaluated using a velocity-voidage correlation for hindered settling of the suspensions;When judged on the basis of the sludge concentration profiles and resulting underflow concentrations from the continuous thickener, the thickening performance of the sludges examined in this investigation was significantly affected by the sludge aggregate characteristics. Correlations between aggregate characteristics and permeability and compressibility explained the differences in thickening behavior;The occurrence of channeling in the compression zone was a function of aggregate characteristics for the diatomaceous earth suspensions, whereas compression zone channeling occurred for all softening sludges examined in this investigation, regardless of aggregate properties;Raking the compression zone obliterated channeling, causing poorer thickening performance of those suspensions which channeled in the compression zone.</p