Laboratory Treatability Studies

Most SBR systems for treatment of industrial wastewaters, especially those containing hazardous wastes, must be designed based on treatability studies. This section outlines the procedures and equipment needed to perform these studies. Figure 11.18.4 illustrates a laboratory SBR system.

The reactors are 1-L to 4-L reaction kettles, typically covered to control volatile organics. The small reactors require less influent wastewater and effluent disposal, and the larger reactors allow collection of larger sample volumes. A gas collection tube, containing activated carbon or other organic absorbent, prevents the escape of volatile organics and measures the extent of organic volatilization. Two gas collection tubes are connected in series to prevent volatile organics in laboratory air from contributing to those released from the reactor. The reactor can be mixed with or without aeration using a magnetic stirrer and a star-head stir bar. Air is supplied through a diffuser from a laboratory air supply. A gas collection tube containing an organic absorbent may be used to prevent or-ganics in the supply air from entering the SBR (not illustrated). To minimize evaporation during SBR aeration, a water humidifier is included in the air stream. Peristaltic tubing pumps add influent and remove effluent from the

Day 1 noon

Day 2 noon

Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D

6am mid

6am mid

Tank 1

S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R

Tank 2

R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs

FIG. 11.18.2 Design flow conditions (i.e., constant flow rate). Illustrations show static fill (Fs), aerated fill (Fa), react (R), settle (S), draw (D), and idle (I) for a three-tank system. Fill periods are shaded to demonstrate that inflow continuously occurs into one of the three tanks, and draw periods are cross-hatched to show the periodic nature of effluent flow.

Tank 3

Day 1 noon

Day 2 noon

Fs Fa R S D I Fs Fa R S D I Fs Fa R S D I Fs Fa R S D Fs Fa R

Fs Fa R

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