Electronic Particle Size Counting. In electronic particle size counting, particles in wastewater are counted by diluting a sample and then passing the diluted sample through a calibrated orifice or past laser presence of the particle. The conductivity is correlated to the size of an equivalent sphere. In a sIml beams. As the particles pass through the orifice, the conductivity of the fluid changes, owing to th fashion, as a particle passes by a laser beam, it reduces the intensity of the laser because of light scattering The reduced intensity is correlated to the diameter of the particle. The particles that are counted are grouped into particle size ranges(e.g,, 0.5 to 2, 2 to 5, 5 to 20 um, etc). In turn, the volume fraction corresponding to each particle size range can be computed Typical effluent volume fraction data from two activated treatment plant are reported on Fig. 2-5. As shown, the particl data for small particles are the same for both treatment However, the particle size data for the large particles are quite different owing primarily to the design and operation of the secondary clarification. Particle size information such as that shown on Fig. 2-5, is useful in assessing the performance of condary sedimentation facilities, effluent filtration, and the potential for chlorine and ultraviolet radiation disinfection Fig. 2-4 Imhoff cone used to determine settleable solids in wastewater Solids that accumulate in the bottom of the cone after 60 min are reported as mL/L Microscopic Observation. Particles in wastewater can also be enumerated microscopically by placing a small sample in a particle counting chamber and counting the individual particles. To aid in differentiating different types of particles, various types of stains can be used. In general, microscopic counting of particles is impractical on a routine basis. Nevertheless, this method can be used to qualitatively assess the nature and size of the particles in wastewater. A quantitative assessment of wastewater particles can be obtained with a microscope by means of a process called optical imaging A small sample of wastewater is placed on a microscope slide. The images of the o Plant 1-3.4 m(11 ft)side water depth Plant 2-5.5 m(18 ft) side water depth wastewater particles are collected with a video camera attached to a microscope and transmitted to a computer where various measurements of the wastewater particles 5 Volume fraction of particle found in the effluent from two activated-sludge plants with clarifiers having diferent side water depths Log of particle diameter The types of measurements that can be obtained are dependent on the computer software but typically include the mean, minimum, and maximum diameter, the aspect ratio(length to width ratio), the circumference, the surface area, the volume, and the centroid of various particles. Particle imaging greatly reduces the time required to measure various characteristics of wastewater particles, but the cost of the software and equipment is often prohibitive for many small laboratories Turbidity Turbidity a measure of the light-transmitting properties of water. is another test used to indicat quality of waste discharges and natural waters with respect to colloidal and residual suspended matter. measurement of turbidity is based on comparison of the intensity of light scattered by a sample to the light 2-72-7 Electronic Particle Size Counting. In electronic particle size counting, particles in wastewater are counted by diluting a sample and then passing the diluted sample through a calibrated orifice or past laser beams. As the particles pass through the orifice, the conductivity of the fluid changes, owing to the presence of the particle. The conductivity is correlated to the size of an equivalent sphere. In a similar fashion, as a particle passes by a laser beam, it reduces the intensity of the laser because of light scattering . The reduced intensity is correlated to the diameter of the particle. The particles that are counted are grouped into particle size ranges (e.g., 0.5 to 2, 2 to 5, 5 to 20 μm, etc). In turn, the volume fraction corresponding to each particle size range can be computed. Typical effluent volume fraction data from two activated sludge treatment plant are reported on Fig. 2-5. As shown, the particle size data for small particles are the same for both treatment plants. However, the particle size data for the large particles are quite different, owing primarily to the design and operation of the secondary clarification . Particle size information, such as that shown on Fig. 2-5 , is useful in assessing the performance of secondary sedimentation facilities, effluent filtration, and the potential for chlorine and ultraviolet radiation disinfection. Fig. 2-4 Imhoff cone used to determine settleable solids in wastewater.Solids that accumulate in the bottom of the cone after 60 min are reported as mL/L Microscopic Observation. Particles in wastewater can also be enumerated microscopically by placing a small sample in a particle counting chamber and counting the individual particles. To aid in differentiating different types of particles, various types of stains can be used. In general, microscopic counting of particles is impractical on a routine basis. Nevertheless, this method can be used to qualitatively assess the nature and size of the particles in wastewater. A quantitative assessment of wastewater particles can be obtained with a microscope by means of a process called optical imaging. A small sample of wastewater is placed on a microscope slide. The images of the wastewater particles are collected with a video camera attached to a microscope and transmitted to a computer where various measurements of the wastewater particles can be assessed. Fig. 2-5 Volume fraction of particle sizes found in the effluent from two activated-sludge plants with clarifiers having different side water depths The types of measurements that can be obtained are dependent on the computer software but typically include the mean, minimum, and maximum diameter, the aspect ratio (length to width ratio), the circumference, the surface area, the volume, and the centroid of various particles. Particle imaging greatly reduces the time required to measure various characteristics of wastewater particles, but the cost of the software and equipment is often prohibitive for many small laboratories. Turbidity Turbidity, a measure of the light-transmitting properties of water, is another test used to indicate the quality of waste discharges and natural waters with respect to colloidal and residual suspended matter. The measurement of turbidity is based on comparison of the intensity of light scattered by a sample to the light