Environmental Engineering Reference
In-Depth Information
containing a number of cassettes immersed in a membrane tank. Multiple process trains
form a ZeeWeed treatment plant.
39.2.3 Treatment Process
Feed water lows into the membrane tanks and treated water is drawn through the mem-
branes during production by applying a vacuum to the inside of the membrane ibers. The
water removed by permeation is replaced with feed water to maintain a constant level in
the tank.
The particles that are rejected by the membrane pores remain in the process tank and
are periodically removed by a process called a backwash. During a backwash, iltered
water is reversed through the membrane iber to dislodge any particles that may be physi-
cally lodged in the membrane iber. Simultaneously, aeration scours any solids that are
attached on the surface of the ibers.
39.2.4 Coupling ZeeWeed to Upstream Processes
ZeeWeed membrane systems can remove particles that are larger than the pores on the
membrane iber. Contaminants that exist in dissolved form, or are smaller than the pore
size, can also be removed by the membranes if they are irst transformed into insoluble
species or larger particles. Treatment processes commonly coupled to ZeeWeed to accom-
plish such conversions include enhanced coagulation and oxidation. Typical examples you
can achieve via this treatment process are found in Table 39.1.
TABLE 39.1
Treatment Results
Potable/Process Water
Turbidity
<0.05 NTU
Bacteria
>4 log removal
Giardia
cysts
>4 log removal
Cryptosporidium
oocysts
>4 log removal
Virus rejection
>2.5 log
Total suspended solids
<1 mg/L
Total organic carbon
50%-90% removal
a
Color
<5 PCU
Iron
<0.05 mg/L
Manganese
<0.02 mg/L
SDI
<1
Wastewater Effluent (as Part of an MBR Process)
BOD
<2 mg/L
TSS
<2 mg/L
NH
3
-N
<0.5 mg/L
TN
<3 mg/L
b
TP
<0.05 mg/L
b
Turbidity
<0.2 NTU
Fecal coliform
<10 CFU/100 mL
Transmissivity
>75%
a
With coagulant addition.
b
With appropriate design and/or chemical addition.
