On-Site Wastewater Treatment and Disposal Systems - Forced ...

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can slough off the sidewall. These factors tend to make the sidewall clogging less severe than the bottom surface. However, the hydraulic gradient across the sidewall mat is also less. At the bottom surface, gravity, the hydrostatic pressure of the ponded water above, and the matric potential of the soil below the mat contribute to the total hydraulic gradient. At the .sidewall, the gravity potential is zero, and the hydrostatic potential diminshes to zero at the liquid surface. Be- cause the matric potential varies with changing soil moisture condi- tions, it is difficult to predict which infiltrative surface will be more effective. In humid regions where percolating rainwater reduces the matric potential along the sidewall, shallow trench systems are suggested (41. The bottom area is the principal infiltrative surface in these systems. Shallow trenches often are best because the upper soil horizons are usually more permeable and greater evapotranspiration can occur. In dry climates, the sidewall area may be used to a greater extent. The bottom area may be reduced as the sidewall area is increased. Common practice is not to give credit to the first 6 in. (15 cm) of sidewall area mea- sured from the trench bottom, but any exposed sidewall above 6 in. (15 cm1 may be used to reduce the bottom area (3)(11). The infiltration rates given in Table 7-2 may be used for sidewall areas. Trench versus Bed Design: Because beds usually require less total land area and are less costly to construct, they are often installed instead of trenches. However, trenches are generally more desirable than beds (4)(11)(12)(13)(14). Trenches can provide up to five times more sidewall area than do beds for identical bottom areas. Less damage is likely to occur to the soil during construction because the excavation equipment can straddle the trenches so it is not necessary to drive on the infiltrative surface. On sloping sites, trenches can follow the contours to maintain the infiltrative surfaces in the same soil horizon and keep excavation to a minimum. Beds may be acceptable where the site is relatively level and the soils are sands and loamy sands. Shallow versus Deep Absorption Systems: Shallow soil absorption systems offer several advantages over deep systems. Because of greater plant and animal activity and less clay due to eluviation, the upper soil horizons are usually more permeable than the deeper subsoil. Also, the plant activity helps reduce the loading on the system during the growing season by transpiring significant amounts of liquid and removing some nitrogen and phosphorus from the waterwater. Construction delays due to wet soils are also reduced because the upper horizons dry more quickly. On the other hand, deep systems have advantages. Increased depths permit increased sidewall area exposure for the same amount of bottom area. They also permit a greater depth of liquid ponding which increases the 216
hydraulic gradient across the infiltrative surface. In some instances deep systems can be used to reach more permeable soil horizons when thi proximity of groundwater tables do not preclude their use. Freezing of shallow absorption systems is not a problem if kept in continuous operation (4)(11). Carefully constructed systems with 6 to 12 in. (15 to 30 cm) of soil cover, which are in continuous operation, will not freeze even in areas where frost penetration may be as great as 5 ft (1.5 m) if the distribution pipe is gravel packed and header pipes insu- lated where it is necessary for them to pass under driveways or other areas usually cleared of snow. Alternating Systems: Dividing the soil absorption system into more than one field to allow alternate use of the individual fields over extended periods of time can extend the life of the absorption system. Alterna- ting operation of the fields permits part of the system to "rest" peri- odically so that the infiltrative surface can be rejuvenated naturally through biodegradation of the clogging mat (4)(11)(12)(13)(15)(16). The "resting" field also acts as a standby unit that can be put into immedi- ate service if a failure occurs in the other part of the system, This provides a period of time during which the failed field can be rehabili- tated or rebuilt without an unwanted discharge. Alternating systems commonly consist of two fields. Each field contains 50 to 100% of the total required area for a single field. Common practice is to switch fields on a semiannual or annual schedule by means of a diversion valve (see Figure 7-3 and Chapter 8). Though it has not yet been proven, such operation may permit a reduction in the total system size. In sandy soils with a shallow water table, the use of alternating beds may increase the chance of groundwater contamination because of the loss of treatment efficiency when the clogging mat is decomposed after resting. c. Layout of the System Location: Locating the area for the soil absorption system should be done with care. On undeveloped lots, the site should be located prior to locating the house, well, drives, etc., to ensure the best area is reserved. The following recommendations should be considered when locating the soil absorption system: 1. Locate the system where the surface drainage is good. Avoid depressions and bases of slopes and areas in the path of runoff from roofs, patios, driveways, or other paved areas unless surface drainage is provided. 217
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DE SIGN MANUAL WASTEWATER TREATMENT
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FOREWORD Rural and suburban communi
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Chapter CONTENTS Page FOREWORD ACKN
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Number FIGURES Wastewater Managemen
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FIGURES Number Page ne Saturator Sa
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FIGURES Number Page Use of Metal Ho
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Number TABLES Selection of Disposal
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Number TABLES (continued) Operati o
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TABLES (continued) Number Page of D
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In many areas, onsite systems have
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2.1 Introduction CHAPTER 2 STRATEGY
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subsurface soil absorption is the p
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features of the site (See 3.3.1 and
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2.2.2 System Selection With the pot
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2.2.4 Onsite System Management Past
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determined largely by the physical
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16 - I ,
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Step Client Contact Preliminary Eva
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FIGURE 3-2 EXAMPLE OF A PORTION OF
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Property USDA Texture Flooding Dept
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TABLE 3-3 SOIL SURVEY REPORT INFORM
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found for a subsurface soil absorpt
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Instrument Supported - Abney Level:
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FIGURE 3-8 PREPARATION OF SOIL SAMP
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Sandy Loam + _. ,i . L Silt Loam Cl
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Depth (Ft.) 0 2 4 6 8 10 12 14 Text
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Grade Structureless Weak Moderate S
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Excavated Soil Material (Tamped in
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If test results agree with this tab
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Percolation test FIGURE 3-15 PERCOL
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mm..--- - --- FIGURE 3-16 COMPILATI
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FIGURE 3-16 (continued) 0 Texture S
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13. Winneberger, J. T. Correlation
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is the overall socioeconomic status
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FIGURE 4-l FREQUENCY DISTRIBUTION F
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extreme, however, minimum and maxim
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4i2.2.2 Individual Activity Contrib
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and the resultant wastewater charac
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TABLE 4-7 TYPICAL WASTEWATER FLOWS
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TABLE 4-9 FIXTURE-UNITS PER FIXTURE
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4.3.2 Wastewater Quality The qualit
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* FIGURE 4-3 STRATEGY FOR PREDICTIN
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12. Witt, M. Water Use in Rural Hom
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5.2 Water Conservation and Wastewat
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5.2.2 Water-Saving Devices, Fixture
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TABLE 5-2 (continued) Total Flo Red
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Generic Typea Description Pit Privy
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TABLE 5-4 WASTEWATER FLOW REDUCTION
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5.2.2.3 Clotheswashing Devices and
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Generic Typea Description Mixing Va
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TABLE 5-6 WASTEWATER FLOW REDUCTION
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TABLE 5-7 EXAMPLE POLLUTANT MASS RE
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FIGURE 5-l EXAMPLE STRATEGIES FOR M
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In most situations, projections of
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FIGURE 5-3 FLOW REDUCTION EFFECTS O
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5.7 References 1. 2. 3. 4. 5. 6. 7.
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6.1 Introduction CHAPTER 6 ONSITE T
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l SauJUOdtUo3 lesodsip pue JuJmeJJa
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318QaQEi33aNON 01-9 3msu simaotld N
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SNOIlQ~tl9I~N03 1NQld 39QI3Qd NOIlQ
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El-9 31av1 S3ItX-US 01313 1INt-l 31
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d. Method of Aeration Oxygen is tra
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contain electrical components, they
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control that results in power savin
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TABLE 6-16 OPERATIONAL PROBLEMS--EX
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I TRICKLING FILTFR FIGURE 6-12 EXAM
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presents suggested design ranges fo
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Item Media Tank Aeration System RBC
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Observation Filter Ponding Filter F
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TABLE.6-21 HALOGEN PROPERTIES (27)
Page 184 and 185: The use of chlorine as a disinfecta
Page 186 and 187: HOC1 , would predominate. It is cle
Page 188 and 189: 6.5.2.5 Construction Features a. Fe
Page 190 and 191: e Wastewater FIGURE 6-14 IODINE SAT
Page 192 and 193: (experience with some units indicat
Page 194 and 195: directing flow through and around t
Page 196 and 197: FIGURE 6-17 TYPICAL UV STERILIZING
Page 198 and 199: Shigella TABLE 6-25 UV DOSAGE FOR S
Page 200 and 201: Cleaning of quartz glass enclosures
Page 202 and 203: the bubble diffuser units to lo-30
Page 204 and 205: TABLE 6-26 POTENTIAL ONSITE NITROGE
Page 206 and 207: Nitrification of septic tank efflue
Page 208 and 209: Influe? Effluent 0 Tank Denitrifica
Page 210 and 211: solution. It can be used to remove
Page 212 and 213: TABLE 6-27 POTENTIAL ONSITE PHOSPHO
Page 214 and 215: Anionic polyelectrolytes can be use
Page 216 and 217: component of the onsite treatment s
Page 218 and 219: 7. 8. 9. 10. 11. 12. 13. 14. 15. 16
Page 220 and 221: 30. 31. 32. 33. 34. 35. 36. 37. 38.
Page 222 and 223: 58. 59. 60. 61. 62. 63. 64. 65. 66.
Page 224 and 225: 7.1 Introduction CHAPTER 7 DISPOSAL
Page 226 and 227: 7.2.1.2 System Selection The type o
Page 228 and 229: Distribution FIGURE 7-2 TYPICAL BED
Page 230 and 231: TABLE 7-l SITE CRITERIA FOR TRENCH
Page 232 and 233: TABLE 7-2 RECOMMENDED RATES OF WAST
Page 236 and 237: FIGURE 7-3 ALTERNATING TRENCH SYSTE
Page 238 and 239: FIGURE 7-4 PROVISION OF A RESERVE A
Page 240 and 241: FIGURE 7-5 TRENCH SYSTEM INSTALLED
Page 242 and 243: TABLE 7-4 DOSING FREQUENCIES FOR VA
Page 244 and 245: The depth of the porous media may v
Page 246 and 247: Distr Pipe, FIGURE 7-6 TYPICAL INSP
Page 248 and 249: against freezing and to stabilize .
Page 250 and 251: Pertodic Deternvne Cause u O&loadin
Page 252 and 253: oils, and greases, can cause failur
Page 254 and 255: 4" Inspection Pip FIGURE 7-9 SEEPAG
Page 256 and 257: The same guidelines used in locatin
Page 258 and 259: Straw, Hay or Fabric? FIGURE 7-10 T
Page 260 and 261: I tern Landscape Position Slope Typ
Page 262 and 263: The acceptable depth to an impermea
Page 264 and 265: FIGURE 7-12 PROPER ORIENTATION OF A
Page 266 and 267: Mound Height TABLE 7-9 DIMENSIONS F
Page 268 and 269: Example 7.1: Calculation of Mound D
Page 270 and 271: 1.0 + 1.4 = - t 0.75 + 1.5 1 [ = (3
Page 272 and 273: . Fill Placement Step 1: Place the
Page 274 and 275: 7.2.4.6 Considerations for Multi-Ho
Page 276 and 277: 7.2.5.2 Application a. Site Conside
Page 278 and 279: 7.2.6 Artificially Drained Systems
Page 280 and 281: ---- FIGURE 7-17 UNDERDRAINS USED T
Page 282 and 283: periods, particularly on level site
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TABLE 7-11 DRAINAGE METHODS FOR VAR
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high water table elevation. To prev
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FIGURE 7-18 TYPICAL ELECTRO-OSMOSIS
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7.2.8.1 Design a. Single Line . Sin
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Inlet From Pretreatment or Previous
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watertight Pipe & Joints1 FIGURE 7-
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ox networks (see Figure 7-23). Howe
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280 s P 4
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FIGURE 7-26 LATERAL DETAIL - TEE TO
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To simplify the design of small pre
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FIGURE 7-29 RECOMMENDED MANIFOLD DI
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Step 3: Select lateral diameter. Fo
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Step 8: Select proper pump or sipho
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Friction loss in 25 ft 2. Velocity
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FIGURE 7-32 DISTRIBUTION NETWORK FO
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In summary, the final network desig
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7.2.8.3 Construction FIGURE 7-33 SC
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Since the network is pressurized, s
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FIGURE 7-35 CROSS SECTION OF TYPICA
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The capillary rise characteristic o
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The hydraulic loading rate is deter
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during the critical months of the y
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7.3.3 Evaporation and Evaporation/I
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FIGURE 7-37 TYPICAL EVAPORATION/INF
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October November December January F
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7.3.3.7 Seasonal, Multifamily, and
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13. 14. 15. 16. 17. 18. 19. 20. 21.
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38. 39. 40. 41. 42. 43. 44. 45. 46.
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The grease traps discussed here are
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Type of Fixture Restaurant kitchen
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Removable Slab Inlet --CL Tee with
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- 8.3.3 Factors Affecting Performan
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The pumping head is calculated by a
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liquid level drops, the weights los
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8.3.5 Construction The tank must be
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Hori FIGURE 8-6 TOP VIEW OF DIVERSI
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9.1 Introduction CHAPTER 9 RESIDUAL
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Parameter TABLE 9-2 CHARACTERISTICS
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Parameter Total Coliform Fecal Coli
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9.4.1 Land Disposal Four methods ca
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TABLE 9-4 (continued) Alternative D
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W z Process Lagooning (1)(13)(14) (
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Process Description Liouid Stream S
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11. 12. 13. 14. 15. 16. 17. 18. 19.
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Some of the techniques discussed ma
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10.3.1 State Agencies Except for th
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10.3.4.1 Private Nonprofit Institut
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10.4.1.1 Standards for Site Suitabi
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Scope of Activities Perform inspect
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Scope of Activities Perform necessa
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10.4.4.1 Inspections Inspections co
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SYSTEM 1. U.S. Bureau of Reclam$t~o
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FIGURE A-2 TEXTURAL TRIANGLE DEFINI
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Class Platelike. with one dimension
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saturation may be necessary to conf
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the porosity of soils containing mo
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FIGURE A-5 SOIL MOISTURE RETENTION
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A.3.3 Flow of Water Through Layered
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GLOSSARY A horizon: The horizon for
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following chemical flocculation; wi
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floodway: A channel built to carry
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ped: A unit of soil structure such
Page 408 and 409:
solids: Material in the solid state
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TECHNICAL REPORT DATA (Please read
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