Lawrence K. Wang

Identification and determination of ionic surface active agents.

A general colorimetric method has been developed to analyze either anionic or cationic surfactants in fresh water. An appropriate dye will react with ionic surfactant to form a chloroform-soluble, colored complex in the presence of chloroform. The color intensity of the vigorously rocked and subsequently settled chloroform layer is proportional to the concentration of the “dye-ionic surfactant complex”, and can then be measured by making spectrophotometric readings of the chloroform solution at the optimum wavelength of the instrument used. When cationic surfactants are to be analyzed, methyl orange shall be used as a dye; when anionic surfactants are to be analyzed, azure A or methylene blue shall be used as a dye. Other chemical reagents, apparatus and spectrophotometers, however, can be nearly identical for either cationic surfactant or anionic surfactant measurement. This new analytical method is stoichiometric, and can be easily performed by a laboratory technician within a very short period of time.

Fundamentals of Wastewater Flotation

The main focus of this chapter is the scientific analysis of flotation for wastewater treatment. The analysis includes a brief description of where and why flotation is used and with what intent. The physical and chemical theories of flotation as they pertain to wastewater flotation, such as characteristic bubble size and its modification, specific contact angles and their control, reactor flow-through pattern, etc. are discussed. Some more frequently encountered versions of flotation reactors are given, together with some illustrating data on the actual plant performance. Furthermore, a rational method to obtain optimum designs of flotation plants and to operate given plants under optimal conditions is described. Here, preparatory investigations and laboratory studies parallel with large-scale operation can be valuable. The design engineer will also be interested in a survey of data on process efficiency as found in the literature along with first estimates on the costs of this flotation process.

Gas Dissolution, Release, and Bubble Formation in Flotation Systems

The theories and principles of gas dissolution, release, and bubble formation in gas flotation systems are introduced in detail for process design, optimization, and operation. Also introduced is a new instrument for real-time measurement of bubble content and size distribution in a typical flotation system consisting of gas bubbles (gas phase) and bulk water (liquid phase). Specific engineering topics included in this chapter are: gas dispersion principles, gas dispersion tester, bubble tester operation, gas dispersion example, gas transfer principles, Henry’s Law constants, partial pressures, solubilities of various gases, gas dissolution and release, gas bubble formation and size distribution, bubble attachment, bubble rising and flotation, gas dissolution in water containing high dissolved solids or high salinity, and engineering design examples.

Remediation of Heavy Metals in the Environment

The feasibility of recycling filter backwash water and alum sludge generated from water purification plants has been investigated. Actual wastewater and alum sludge used in this study were collected from a water plant employing water treatment processes including chemical addition, mixing, flocculation, clarification, filtration, and chlorination. Wastewater and sludge are generated mainly from the clarifier and the filter backwash. The waste recycle system presented here consists of (a) recycling the filter backwash water to the intake system for the reproduction of potable water, (b) dividing the combined sludge into two fractions for alum solubilization, separately, in an acid reactor and an alkaline reactor, (c) removing the inert silts from alum solutions by two separate water–solids separators for ultimate disposal, and (d) returning the solubilized alums from the two separate water–solids separators in proper proportions for reuse as flocculants. CONTENTS Abstract ............................................................................................................................................ 49 3.

Principles and Kinetics of Biological Processes

Biological technologies can be used to treat a vast majority of organic wastewaters because all organics could be biologically degraded if the proper microbial communities are established, maintained, and controlled. Before environmental engineers design and operate biological treatment systems that create the environment necessary for the effective treatment of wastewater, a sound understanding of the fundamentals of microbial growth and substrate use kinetics is essential. This chapter covers the above including basic microbiology and kinetics, kinetics of activated sludge process, factors affecting the nitrification process, kinetics of the nitrification process, denitrification by suspended growth systems and design examples.

Emerging Suspended-Growth Biological Processes

Among the emerging suspended-growth biological treatment processes covered in this chapter are powdered activated carbon treatment (PACT) process, carrier-activated sludge process (CAPTOR and CAST systems), activated bio-filter (ABF), vertical loop reactor (VLR), and phostrip process. This chapter describes the above processes and explains their practice, limitations, design criteria, energy requirements, process equipment, performance, and costs.

Algae Removal by Flotation

The importance of algae is discussed. Algae are a significant source of oxygen on Earth due to its capability of photosynthesis. Further they are an efficient biological system for converting solar energy into plant life, a source of energy for higher life. However, at high concentrations, called blooms, they can contribute tastes and odors, and even toxins to the surrounding water. They are best removed before they reach a water treatment plant (WTP) where they may rupture and release their taste and odor oils. Algae at both low and high concentrations may be removed by dissolved air flotation (DAF). Even very high concentrations from wastewater treatment lagoons and algae culture ponds are efficiently removed. The recovered algae have many economical uses. When alum or iron salts are added to improve coagulation for algae removal, phosphorus is also removed, thereby lessening productivity in a lake or stream. The development of algae culture ponds heated by waste heat from a nearby power plant, combined with CO2 and NO X from fossil fueled power plants’ atmospheric discharges, could reduce atmospheric pollution and even global warming. The algae produced and removed can serve as an energy source. A case study is described for the application of a DAF system for upgrading a small drinking WTP. Examples are shown for the separation of algae from wastewater treatment plant lagoons. The use of DAF for separation of algae is an important factor in our lives.

Pure Oxygen Activated Sludge Process

The use of pure oxygen for activated sludge treatment has become competitive with the use of air owing to the development of efficient oxygen dissolution systems. The pure oxygen system may be used for aeration in activated sludge systems that operate in either the plug flow or complete mix hydraulic regimes. It is readily adaptable to new or existing complete mix systems and can be used to upgrade and extend the life of overloaded plug-flow systems. The amount of oxygen that can be injected into the liquid (for a specific set of conditions) is approximately four times the amount that could be injected with an air system. In addition to process description, this chapter discusses covered and uncovered units, design considerations, design parameters and design procedure.

Treatment of Paper Mill Whitewater, Recycling and Recovery of Raw Materials

The characteristics and application of titanium dioxide and other fillers in the paper industry are introduced, the filler retention is defined, and the resources in whitewater and conventional processes are presented. Topics covered include a description of the paper industry, paper mill discharges, whitewater treatment and reuse, raw material recovery, opacity and fillers, available treatment technologies, and a study of a dissolved air flotation (DAF) process for recovery of fiber and titanium dioxide. The opacifying power of titanium dioxide as usually recovered by DAF is diminished by the persistence of the flocs necessary for the flotation. A recovery simulation to overcome that deficiency is described in which a cationic starch is used as the flotation aid, and the recovered solids are deflocced with enzymes. Handsheets were formed incorporating titanium recovered in this fashion for comparison with ones made with virgin titanium dioxide. The handsheets formed from this process had optical properties similar to those of papers made with the same amount of virgin filler over a large range of titanium dioxide contents in the paper.

Flotation Biological Systems

Dissolved air flotation, air dissolving tube, friction valve, flotation chamber, spiral scoops, flotation system configurations, and flotation biological systems (FBS) for conventional activated sludge process with sludge recycle are considered in the chapter. The case studies of FBS treatment systems in petrochemical industry effluent treatment, municipal effluent treatment, and paper manufacturing effluent treatment, altogether with operational difficulties and their remedy are described in the chapter.