Calculation of Anaerobic Filters For DWTS

Anaerobic Filters calculation depends of various parameters like void ratio of media and height ratio of different type of material. but there i have provided with some calculation steps. you can calculate the AF design if you have information about various parameters.

                                                     Anaerobic Filter

Standards
HRT = 8 hrs                                                                       (Decentralized waste water treatment systems )
OLR = 6 kg BOD/m3/d                         (Sasse, 1998)
OLR = 4 – 5 kg COD/m3/d
Filter Material = Cinder, PVC Pipe Pieces, Crushed Glass
Length of a chamber < Depth
Design
Depth allowed = 1.8 m                                    
Filter media depth = 1.2 m        (Cinder 0.3 m, PVC Pipe Pieces 0.6 m, Crushed Glass 0.3 m)
Bottom sludge zone = 0.3 m
Top water zone = 0.3 m
Free board = 0.5 m                   (Total Depth = 2.3 m)
HRT = 12 hrs
Wastewater Volume = 6.67 * 12 = 80 m3
Void Ratio of media = 0.5
Media Volume = 0.5 * 80 = 40 m3
Total wetted volume required = 120 m3
Wetted Width = Width of ABR = 8 m  (For both units)
Wetted Depth = 1.2 m (excluding top water zone and bottom sludge zone)
Wetted Length = Wetted Volume / (Depth * Width)
            = 120 / (1.2*8) = 12.5 m
Total units = 3
Length of each unit = 12.5/3 = 4.2 m ≈ 4 m
Upflow velocity: 3.335/(4 * 4) = 0.2 m/hr < 2 m/hr
Total Volume of each AF including Freeboard = Length of chamber x No. of Chambers x Width x Depth
                                                                    = 4 * 3 * 4 * 2.3
                                                                    = 110.4 m3 (Freeboard from top to facilitate inspection)
Use 2 AFs for two trains each having 3 compartments. Volume of each AF per train = 110.4 m3

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