FLOW DISTRIBUTION BOX

JOSEPH SCHUECK, P.E, P.G.

AGRI DRAIN MANUFACTURERS REPRESENTATIVE

Passive treatment sizingBased on loading:

Expressed in terms of gm/sq m/day

flow x chemistry

Based on detention time: Expressed in terms of volume

flow x time

Regardless of whether the system is a VFP, a bioreactor or a

limestone pond, flow is a critical factor!

During pre-design monitoring, the chemistry of the discharge is

fairly easy to define

Flow is much more difficult to define.

RZW and Z1 Daily Discharge

0

25

50

75

100

125

150

175

200

225

Oct

-97

No

v-97

Dec

-97

Jan

-98

Feb

-98

Mar

-98

Ap

r-98

May

-98

Jun

-98

Jul-

98

Dis

char

ge

gp

m

RZW

Z1

Flow monitoring can be quite deceptive~!!!

 Z1

% of days Z1

% of days RZW

% of days RZW

% of days

 monthly exceeded daily

exceeded monthly exceeded daily exceeded

average 103 63% 107.6 62% 25 37% 33.6 23%

90th%tile 139 16% 146 9% 36 22% 88 10%

During construction it is not uncommon to encounter

additional flows.

Some sites are simply limited in available space and the designer

simply builds as large as possible. Such a system is under

designed from the getgo.

Rarely are any controls put in place to limit or meter the flow

going into a passive system.

Dr. Art Rose investigated system performancePoor performance reasons included:

Too much flow for the systemLoading too high for the system

Decreasing flow would likely have improved performance