Solids, suspended

Suspended solids are typically measured using turbidity. Turbidity measures the light-scattering ability of particles in water. The water quality guidelines call for an influent turbidity of less than 1 Nephelometric Turbidity Units (NTU), which also happens to be a warranty requirement of membrane manufacturers. Exceed 1 NTU and the membrane warranty is voided. The 

Another measure of suspended solids is particle size distribution. However, there are no recommendations on particle size distribution in RO feed water that have been established. In general, particle size distributions have a lower limit of 0.5 im, while the particles of importance with respect to membrane following may be much smaller in size. 

Produced water and oil contain very small particulate solid matter held in suspension in the liquid phase by surface tension and electrostatic forces. This solid matter is referred to as a suspended solid and may consist of small particles of sand, clay, precipitated salts and flakes of scale, and products of corrosion such as iron oxide and iron carbonate. When suspended solids are measured by weight or volume, the composite measurement is referred to as the total suspended solids (TSS) content. Chapter 3 provides a detailed discussion on suspended solids. 

Under certain conditions, the dissolved solids precipitate or crystallize from the produced water to form solid deposits in pipe and equipment. These solid deposits are referred to as scale. The most common scales include calcium carbonate, calcium sulphate, barium sulphate, strontium sulphate, and iron sulfide. Scale is discussed further in Chapter 3. 

An emulsion is an oil and water mixture that has been subjected to shearing resulting in the division of oil and water phases into small droplets. Most emulsions encountered in the oil field are water droplets in an oil continuous phase and are referred to as normal emulsions. Oil droplets in a water continuous phase are referred to as reverse emulsions. Emulsions are discussed further in Chapter 2. 

Clarification may also alter the nutritional status of the must. For instance, Ayestaran et al. (1995) observed that total nitrogen levels in unclarified musts were higher than those clarified by either gravity or vacuum filtration. By comparison, amino nitrogen levels were higher in clarified musts. Ferrando et al. (1998) found no effect of clarification by 

Clarification can be used to reduce populations of non-Saccharomyces yeasts (Mora and Mulet, 1991). Although populations are initially reduced, growth of these yeasts may continue during cold-clarification and actually lead to denser populations than expected. Many of these yeasts may also be active during the course of fermentations conducted at lower temperatures (Section 6.2.2). The presence of insoluble solids in musts also influences subsequent malolactic fermentations (Liu and Gallander, 1982). Here, the authors reported that MLF was most rapid in wines fermented with the highest amount of solids. 

During cold clarification, some microorganism may continue to evolve and grow, leading to denser populations than expected (Mora and Mulet, 1991). Native species such as Pichia membranaefaciens, Candida stellata, and Kloeckera apiculata have been reported to acclimate rapidly during low-temperature clarification conditions (see 4.5). Splittstoesser (1978) re- 

Effects of Pollutants on the Chemistry of the Atmosphere, Hydrosphere, and Lithosphere 

The term settleable solids applies to suspended solids that settle under quiescent conditions because of the influence of gravity. Their measurement is important in engineering practice to determine the need for sedimentation units and the physical behavior of waste streams entering natural water bodies. Colloidal particles do not settle readily and cause the turbidity found in many surface waters. 

In turbid waters, most of the harmful organisms are exposed to the action of a disinfectant. However, in cases in which turbidity is caused by municipal wastewater solids, many of the pathogenic organisms may be encased in the particles and protected from the disinfectant. For this and for aesthetic reasons, the U.S. Environmental Protection Agency has placed a maximum contaminant level of 0.5 to 1.0 units of turbidity in public water supplies, depending on the treatment process. 

Turbidity is a measure of the light-transmitting properties of water. The measurement of turbidity is based on comparison of the intensity of light scattered by a sample to the light scattered by a reference suspension under the same conditions. The most widely used standards are prepared with hydrazine sulfate and hexamethylenetetramine in water, and give rise to the Formazin Turbidity Units (FTU). 

The amount of suspended matter in wastewater increases with the degree of pollution. Sludges 

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Filtration. In filtration, suspended solid particles in a liquid or gas are removed by passing the mixture through a porous medium that retains the particles and passes the fluid. The solid can be retained on the surface of the filter medium, which is cake, filtration, or captured within the filter medium, which is depth filtration. The filter medium can be arranged in many ways. 

In situations where a low concentration of suspended solids needs to be separated from a liquid, then cross-flow filtration can be used. The most common design uses a porous tube. The suspension is passed through the tube at high velocity and is concentrated as the liquid flows through the porous medium. The turbulent flow prevents the formation of a filter cake, and the solids are removed as a more concentrated slurry. 

Ultrafiltration. Ultrafiltration was described under pretreatment methods. It is used to remove finely divided suspended solids, and when used as a tertiary treatment, it can remove virtually all the BOD remaining after secondary treatment. 

Ccasionally the reaction mixture does not become completely black nor free from suspended solid here the acetylide is in an insoluble (or sparingly soluble) form, but it gives satisfactory results in the preparation of hex-l-yne. The saturated solution of the soluble form of mono-sodium acetylide in liquid ammonia at — 34° is about i- M. 

Particulate interferents can be separated from dissolved analytes by filtration, using a filter whose pore size retains the interferent. This separation technique is important in the analysis of many natural waters, for which the presence of suspended solids may interfere in the analysis. Filtration also can be used to isolate analytes present as solid particulates from dissolved ions in the sample matrix. For example, this is a necessary step in gravimetry, in which the analyte is isolated as a precipitate. A more detailed description of the types of available filters is found in the discussion of precipitation gravimetry and particulate gravimetry in Chapter 8. 

Finally, in particulate gravimetry the analyte is determined following its removal from the sample matrix by filtration or extraction. The determination of suspended solids is one example of particulate gravimetry. 

Removing the analyte from its matrix by filtration or extraction must be complete. When true, the analyte s mass can always be found from the analytical signal thus, for the determination of suspended solids we know that... 

Filter s final mass - filter s initial mass = g suspended solid... 

Particulate gravimetry is commonly encountered in the environmental analysis of water, air, and soil samples. The analysis for suspended solids in water samples, for example, is accomplished by filtering an appropriate volume of a well-mixed sample through a glass fiber filter and drying the filter to constant weight at 103-105 °C. 

A 200.0-mL sample of water was filtered through a preweighed glass fiber filter. After drying to constant weight at 105 °C, the filter was found to have increased in mass by 48.2 mg. Determine the total suspended solids for the sample in parts per million. 

Parts per million is the same as milligrams of analyte per liter of solution thus, the total suspended solids for the sample is... 

EPA Process Design Manualfor Suspended Solids Removal, U.S. Environmental Protection Agency Technology Transfer, Washington, D.C., 1975, pp. 5-6. 

In the presence of fine coUoids or suspended solids, the membrane pores may also become plugged. 

Low concentrations of oil can be removed by dissolved air flotation (DAF). In this process, an effluent recycle is pressurized in the presence of excess air, causing additional air to go into solution, in accordance with Henry s Law. When this water is discharged to the inlet chamber of the flotation unit at close to atmospheric pressure, the dissolved air comes out of solution in the form of tiny air bubbles which attach themselves to and become enmeshed in suspended solids and oil globules. The primary design criteria is the air/solids ratio, which is defined as the mass of air released divided by the mass of solids fed. Sufficient air must be released to capture the solids in the influent wastewater. The performance of DAF for the treatment of several... 

Suspended Solids Removal. Depending on the concentration and characteristics of the suspended soflds, they can be removed by filtration, flotation, or sedimentation. Coarse soflds are removed by screening. Settleable suspended soflds are removed in a clarifier, which may be circular or rectangular. The efficiency of soflds removal is a function of the overflow rate (m /-d (gal/ft -d) as shown in Figure 5. 

Suspended Solids. Suspended soflds are determined by filtering a known volume of water through a glass-fiber filter and weighing the filter before and after filtration. The filter is dried at 105—110°C, and the weight difference is equal to the suspended soflds. 

Most surface waters contain varying amounts of suspended solids, including silt, clay, bacteria, and vimses and it is necessary to remove these before to distribution to the domestic or industrial consumer. Suspended soHds not only affect the acceptabiUty of the water but also interfere with disinfection. The principal treatment processes are sedimentation (qv) and filtration (qv). Sedimentation alone is rarely adequate for the clarification of turbid waters and is of htde or no value for the removal of such very fine particles as clay, bacteria, etc. Table 1 shows the effect of particle size on the sedimentation rate of a soHd having a specific gravity of 2.65 in water at 20°C. 

Refs. 22, 23. BOD = Biological oxygen demand. COD = Chemical oxygen demand. TSS liihle 1. (Continued) Total suspended solids. O and G = oil and grease. ... 

In many cases, the quality of a stream or another water source can be adequately improved by removing more BOD or suspended solids. In other iastances, the effluent is prepared for groundwater recharge which may require only the removal of nutrient. A classification of wastewater treatment processes is given ia Table 3. Table 4 summarizes water quality criteria for various iadustrial uses (10). 

From ref. 10 units are mg/L unless otherwise specified. Abbreviations IDS, total dissolved solids SS, suspended solids. 

Presence of Solids When a pump is required to pump a hquid containing suspended solids, there are unique requirements which must be considered. Adequate clear-liquid hydraiilic performance and the use of carefully selected materials of construction may not be all that is required for satisfacdoiy pump selection. Dimensions of all internal passages are critical. Pockets and dead spots, areas where solids can accumulate, must be avoided. Close internal clearances are undesirable because of abrasion. Flushing connections for continuous or intermittent use should be provided. 

Pnettmatically Actuated Diaphragm Pumps (Fig. 10-53) These pumps require no power source other than plant compressed air. They must have a flooded suction, and the pressure is, of course, limited to the available air pressure. Because of their slow speed and large valves, they are well suited to the gentle handling of liquids for which degradation of suspended solids should be avoided. 

Valve Trim Various alloys are available for valve parts such as seats, disks, and stems which must retain smooth finish For successful operation. The problem in seat materials is fivefold (1) resistance to corrosion by the fluid handled and to oxidation at high temperatures, (2) resistance to erosion by suspended solids in the fluid, (3) prevention of galling (seizure at point of contact) by differences in material or hardness or Both, (4) maintenance of high strength at high temperature, and (5) avoidance of distortion. 

Foam Production This is important in froth-flotation separations in the manufac ture of cellular elastomers, plastics, and glass and in certain special apphcations (e.g., food products, fire extinguishers). Unwanted foam can occur in process columns, in agitated vessels, and in reactors in which a gaseous product is formed it must be avoided, destroyed, or controlled. Berkman and Egloff (Emulsions and Foams, Reinhold, New York, 1941, pp. 112-152) have mentioned that foam is produced only in systems possessing the proper combination of interfacial tension, viscosity, volatihty, and concentration of solute or suspended solids. From the standpoint of gas comminution, foam production requires the creation of small biibbles in a hquid capable of sustaining foam. 

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