Methods of Sewage Waste disposal | |
Methods of sewage disposal are of two types:
Mathematically; HRT, tD = (Volume/Discharge) ------- days/hours/sec (units) | |
Flow Through Velocity or Horizontal Velocity and Settling Velocity Settling path of a solids particle in a tank Surface Loading Rate or Overflow Rate is the volume of water/wastewater applied per unit surface area of the treatment basin and is normally expressed in units of m3/m2-d or gal/ft2-d. Mathematically;
SLR = (Flow, Q/Area, As) {Numerically; SLR = HRT}
Weir Loading Rate or Weir Overflow Rate is the quantity of wastewater flowing over a unit weir length of the tank in a unit time. It is expressed in units of m3/m-d or gal/ft-d. Mathematically; WLR = (Flow, Q/Total Length of Weir, L) PROBLEM: A treatment unit is 1.5 ft wide, 20 ft long and has a depth of 2.0 ft. if the wastewater flow rate through the tank is 0.5 ft3/sec. Calculate; detention time, overflow rate and weir loading rate. Organic Loading is the total quantity of organic matter in terms of BOD or COD that is applied per day over the unit surface area of per unit volume of the treatment basin or tank. Mathematically; OLR = (applied kg of BOD per day)/(volume of the basin) It is expressed as kg-BOD/m3-d or kg-COD/m3-d PROBLEM: A treatment basin has a diameter of 20 ft and a depth of 2.5 ft. Calculate the organic loading rate for an effluent of 10.0 MGD having 220 mg/L of BOD. Food-Microorganisms (F/M) Ratio is the relationship between the available food (F) and the microorganism (M) present in a biological treatment system. F/M = [(Q*So)/(V*X)] ----------- it is expressed in unit of sec-1 or d-1 etc. Since, HRT tD = V/Q, therefore, F/M = [So/(tD*X)] PROBLEM: If the wastewater with BOD concentration of 200 mg/L is treated in a tank having 5 hours HRT and containing 4000 mg/L MLVSS, calculate its F/M ratio. Mean Cell Residence Time or Solid Retention Time or Sludge Age; is the average time in days for which biomass are retained in the biological reactors |
Determinacy, Indeterminacy and Stability of Frames : Structural engineers must be able to apply judgment rather than stated rules. The most important aspect of structural design is not the ability to apply formulas or manipulate mathematics. The most important skill for the structural engineer is to be able to stand back, look at a drawing or sketch and determine whether a structure is stable, and if it is stable, to be able to determine how it will carry the applied loads. For a very complicated structure this might be more difficult and a computer can provide some help, but ultimately it is the skill and concern of a good structural engineer which produces good structural designs which have integrity. Another important closely related skill is the ability to determine whether, and to what degree, a structure is statically indeterminate. There really aren’t many rules and rules may be difficult to apply in any case. For this reason, we need experience. A skilled structural...
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