Domestic Wastewater Treatment Mobilization Construction - AskTOP

EM 1110-3-17211 May 84filter are dampened . Filter sloughings are recycled to the filter inflow diagram A, but little, if any, dampening of variations in organicloading is provided . Flow diagram E may include a low-rate filter forthe second-stage unit . Intermediate settling tanks will always beprovided between first and second stage filters . Flow diagrams G and Hattempt to improve treatment by developing greater biological activityon the second stage filter, but are not acceptable for Armyinstallations because there are no intermediate clarifiers . Flowdiagrams E, F, G, and H require inclusion of the recirculated flow inthe forward flow used for design of any tanks through which it passes .Table 10-2 .Design Recirculation Rates for High-Rate FiltersRaw Sewage BOD,mg/l_ Recircula tionlSingle Stne Two StakeUp to 150 1 .0 0 .5150 to 300 2 .0 1 .0300 to 450 3 .0 1 .5450 to 600 4 .0 2 .01 Ratio of recirculated flow to raw wastewater flow2Ratio for each stage ; one half of the single-stage ratec . Hydraulic and organic loadings . Loading rate is the key designfactor, whether the surface application is continuous, intermittent, aconstant rate, or a varying rate . The BOD removal efficienciesobtainable for specific wastewater organic and hydraulic loading fromtrickling filter installations can be compared when the loadings arewithin the ranges presented in table 10-1 and the trickling filterperformance formula described in paragraph 10-2 .f .(1) is utilized .d . Ventilation . Ventilation provides aerobic conditions requiredfor effective treatment . Design for ventilation will provide thefollowing :(1) Underdrains and collecting channels designed to flow halffull at maximum design flow .(2) Ventilating manholes with open grate covers installed atboth ends of the central collecting channel .(3) Branch collecting channels with ventilating manholes orstacks installed at the filter periphery for units over 50 feet indiameter .vent(4) Open area of slots in the top of the underdrain blocks notless than 15 percent of the area of the filter .