Science of Water : Concepts and Applications

More documents

Recommendations

Info

Water Treatment 313 effi ciency with highly turbid waters. On the downside, operation and maintenance costs of rapid sand fi lters are much higher because of the increased complexity of the fi lter controls and backwashing system. In backwashing a rapid sand fi lter, cleaning the fi lter is accomplished by passing treated water backward (upward) through the fi lter media and agitating the top of the media. The need for backwashing is determined by a combination of fi lter run time (i.e., the length of time since the last backwashing), effl uent turbidity, and head loss through the fi lter. Depending on the raw water quality, the run time varies from one fi ltration plant to another (and may even vary from one fi lter to another in the same plant). √ Note: Backwashing usually requires 3–7% of the water produced by the plant. Pressure Filter Systems When raw water is pumped or piped from the source to a gravity fi lter, the head (pressure) is lost as the water enters the fl oc basin. When this occurs, pumping the water from the plant clear well to the reservoir is usually necessary. One way to reduce pumping is to place the plant components into pressure vessels, thus maintaining the head. This type of arrangement is called a pressure fi lter system. Pressure fi lters are also quite popular for iron and manganese removal and for fi ltration of water from wells. They may be placed directly in the pipeline from the well or pump with little head loss. Most pressure fi lters operate at a rate of about 3 gpm/ft2 . Operationally the same, and consisting of components similar to those of a rapid sand fi lter, the main difference between a rapid sand fi ltration system and a pressure fi ltration system is that the entire pressure fi lter is contained within a pressure vessel. These units are often highly automated and are usually purchased as self-contained units with all necessary piping, controls, and equipment contained in a single unit. They are backwashed in much the same manner as the rapid sand fi lter. The major advantage of the pressure fi lter is its low initial cost. They are usually prefabricated, with standardized designs. A major disadvantage is that the operator is unable to observe the fi lter in the pressure fi lter and so is unable to determine the condition of the media. Unless the unit has an automatic shutdown feature on high effl uent turbidity, driving fi ltered material through the fi lter is possible. Diatomaceous Earth Filters Diatomaceous earth is a white material made from the skeletal remains of diatoms. The skeletons are microscopic, and in most cases, porous. There are different grades of diatomaceous earth, and the grade is selected based on fi ltration requirements. These diatoms are mixed in water slurry and fed onto a fi ne screen called a septum, usually of stainless steel, nylon, or plastic. The slurry is fed at a rate of 0.2 lb/ft 2 of fi lter area. The diatoms collect in a precoat over the septum, forming an extremely fi ne screen. Diatoms are fed continuously with the raw water, causing the buildup of a fi lter cake approximately 1/8–1/5 in. thick. The openings are so small that the fi ne particles that cause turbidity are trapped on the screen. Coating the septum with diatoms gives it the ability to fi lter out very small microscopic material. The fi ne screen and the buildup of fi ltered particles cause a high head loss through the fi lter. When the head loss reaches a maximum level (30 psi on a pressure-type fi lter or 15 in. or mercury on a vacuum-type fi lter), the fi lter cake must be removed by backwashing. Slurry of diatoms is fed with raw water during fi ltration in a process called body feed. The body feed prevents premature clogging of the septum cake. These diatoms are caught on the septum, increasing the head loss and preventing the cake from clogging too rapidly by fi ltering of the particles. While the body feed increases head loss, head loss increases are more gradual than if body feed were not used.
314 The Science of Water: Concepts and Applications Although diatomaceous earth fi lters are relatively low in cost to construct, they have high operating costs and can give frequent operating problems if not properly operated and maintained. They can be used to fi lter raw surface waters or surface-infl uenced groundwaters, with low turbidity (
Page 2:
Second Edition THE SCIENCE OF WATER
Page 5 and 6:
Cover Image: Falling Spring at Fall
Page 8 and 9:
Contents Preface ..................
Page 10 and 11:
Contents ix Velocity Head .........
Page 12 and 13:
Contents xi Specifi c Conductance .
Page 14 and 15:
Contents xiii (5) Beetles (Order: C
Page 16 and 17:
Contents xv Chlorine Residual Testi
Page 18:
Contents xvii Water Filtration Calc
Page 22:
To the Reader In reading this text,
Page 26 and 27:
1 Introduction When color photograp
Page 28 and 29:
Introduction 3 On second look, we s
Page 30 and 31:
Introduction 5 As mentioned earlier
Page 32 and 33:
Introduction 7 This scream of lost
Page 34:
Introduction 9 Metcalf & Eddy, Inc.
Page 37 and 38:
12 The Science of Water: Concepts a
Page 39 and 40:
Page 41 and 42:
Page 43 and 44:
Page 45 and 46:
Page 47 and 48:
Page 49 and 50:
Page 51 and 52:
Page 53 and 54:
Page 55 and 56:
Page 57 and 58:
Page 59 and 60:
Page 61 and 62:
Page 63 and 64:
Page 65 and 66:
Page 67 and 68:
Page 70 and 71:
3 Water Hydraulics Anyone who has t
Page 72 and 73:
Water Hydraulics 47 Another relatio
Page 74 and 75:
Water Hydraulics 49 • • 1 ft 3
Page 76 and 77:
Water Hydraulics 51 √ Important P
Page 78 and 79:
Water Hydraulics 53 FIGURE 3.4 Thru
Page 80 and 81:
Water Hydraulics 55 Example 3.8 Pro
Page 82 and 83:
Water Hydraulics 57 FIGURE 3.6 Lami
Page 84 and 85:
Water Hydraulics 59 With regard to
Page 86 and 87:
Water Hydraulics 61 or hydraulic gr
Page 88 and 89:
Water Hydraulics 63 E 1 smaller fl
Page 90 and 91:
Water Hydraulics 65 √ Note: In de
Page 92 and 93:
Water Hydraulics 67 • Cone of dep
Page 94 and 95:
Water Hydraulics 69 • • • •
Page 96 and 97:
Water Hydraulics 71 The Darcy-Weisb
Page 98 and 99:
Water Hydraulics 73 Of course, pipe
Page 100 and 101:
Water Hydraulics 75 In this section
Page 102 and 103:
Water Hydraulics 77 Slope (S) The s
Page 104 and 105:
Water Hydraulics 79 and important c
Page 106 and 107:
Water Hydraulics 81 and the depth o
Page 108 and 109:
Water Hydraulics 83 TYPES OF DIFFER
Page 110 and 111:
Water Hydraulics 85 √ Important P
Page 112 and 113:
Water Hydraulics 87 Meter backpress
Page 114 and 115:
Water Hydraulics 89 VELOCITY FLOWME
Page 116 and 117:
Water Hydraulics 91 The positive-di
Page 118 and 119:
Water Hydraulics 93 Solution: 1200g
Page 120:
Water Hydraulics 95 Water and Waste
Page 123 and 124:
Page 125 and 126:
100 The Science of Water: Concepts
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
Page 143 and 144:
Page 145 and 146:
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 180 and 181:
6 Water Ecology The subject of man
Page 182 and 183:
Water Ecology 157 The environment i
Page 184 and 185:
Water Ecology 159 FIGURE 6.2 Notone
Page 186 and 187:
Water Ecology 161 H 2 O O 2 FIGURE
Page 188 and 189:
Water Ecology 163 FeS FIGURE 6.6 Th
Page 190 and 191:
Water Ecology 165 Algae FIGURE 6.8
Page 192 and 193:
Water Ecology 167 2. Likewise, biom
Page 194 and 195:
Water Ecology 169 Population densit
Page 196 and 197:
Water Ecology 171 succession can be
Page 198 and 199:
Water Ecology 173 dark winter month
Page 200 and 201:
Water Ecology 175 In rain events wh
Page 202 and 203:
Water Ecology 177 long profi le, cr
Page 204 and 205:
Water Ecology 179 THE FLOODPLAIN A
Page 206 and 207:
Water Ecology 181 It is important t
Page 208 and 209:
Water Ecology 183 Specifi c Adaptat
Page 210 and 211:
Water Ecology 185 serve to indicate
Page 212 and 213:
Water Ecology 187 UNITS OF ORGANIZA
Page 214 and 215:
Water Ecology 189 FIGURE 6.20 Stone
Page 216 and 217:
Water Ecology 191 FIGURE 6.22 Midge
Page 218 and 219:
Water Ecology 193 FIGURE 6.25 Riffl
Page 220 and 221:
Water Ecology 195 They push their m
Page 222 and 223:
Water Ecology 197 FIGURE 6.32 Damse
Page 224:
Water Ecology 199 Darwin, C., 1998.
Page 227 and 228:
Page 229 and 230:
Page 231 and 232:
Page 233 and 234:
Page 235 and 236:
Page 237 and 238:
Page 239 and 240:
Page 241 and 242:
Page 243 and 244:
Page 245 and 246:
Page 247 and 248:
Page 249 and 250:
Page 251 and 252:
Page 253 and 254:
Page 255 and 256:
Page 257 and 258:
Page 259 and 260:
Page 261 and 262:
Page 263 and 264:
Page 265 and 266:
Page 267 and 268:
Page 269 and 270:
Page 271 and 272:
Page 273 and 274:
Page 275 and 276:
Page 277 and 278:
Page 279 and 280:
Page 281 and 282:
Page 283 and 284:
Page 285 and 286:
Page 287 and 288: 262 The Science of Water: Concepts
Page 337: 312 The Science of Water: Concepts
Page 350 and 351: 10 Water Treatment Calculations Gup
Page 352 and 353: Water Treatment Calculations 327 We
Page 354 and 355: Water Treatment Calculations 329 Th
Page 358 and 359: Water Treatment Calculations 333 Ex
Page 360 and 361: Water Treatment Calculations 335 me
Page 362 and 363: Water Treatment Calculations 337 Fo
Page 366 and 367: Water Treatment Calculations 341 So
Page 368 and 369: Water Treatment Calculations 343 No
Page 374 and 375: Water Treatment Calculations 349 In
Page 388 and 389:
Water Treatment Calculations 363 St
Page 390 and 391:
Water Treatment Calculations 365 WA
Page 392 and 393:
Water Treatment Calculations 367 St
Page 394 and 395:
Water Treatment Calculations 369 Th
Page 396 and 397:
Water Treatment Calculations 371 So
Page 398 and 399:
Page 400 and 401:
Water Treatment Calculations 375 Ex
Page 402 and 403:
Page 404 and 405:
Water Treatment Calculations 379 Se
Page 406 and 407:
Water Treatment Calculations 381 µ
Page 408 and 409:
Water Treatment Calculations 383 g
Page 410 and 411:
Page 412 and 413:
Water Treatment Calculations 387 No
Page 414 and 415:
Page 416 and 417:
Page 418 and 419:
Page 420 and 421:
Water Treatment Calculations 395 Ca
Page 422 and 423:
Page 424:
Water Treatment Calculations 399 Mo
Page 427 and 428:
Page 429 and 430:
Page 431 and 432:
Page 433 and 434:
Page 435 and 436:
Page 437 and 438:
Page 439 and 440:
Page 441 and 442:
Page 443 and 444:
Page 445 and 446:
Page 447:
show all

Science of Water : Concepts and Applications

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?