Sewage Processing Plants – The particle size distribution and particle charge properties of solids in the final settling tanks

International Environmental TechnologyVol. 11 Issue 6 Nov/Dec 2001

Wolfgang Schubert, F. Wolfgang Gunthert, Renate Hessemann

…The theoretical sedimentation time of a 1-micron particle is around 210 days; for a 10-micron particle it is 50 hours; and for a 100-micron particle 30 minutes. Therefore in the final settling tanks, particles smaller than 100-micron that have sedimentation times of several hours may not settle-out completely…

Figures 1 and 2 show, as an example, the measured particle size distribution (from 6 to 3000-micron) in the final settling tanks of an activated sludge process and from a fixed bed plant respectively…

0

1

2

3

4

5

6

are

a d

istr

ibu

tio

n (

%)

size c l

a ss (mm)

Size class (m)

Activated Sludge Process

Drain Final Setting Tank

Fixed Bed Plant

0

5

10

15

20

25

size class (m)a

rea

dis

trib

uti

on

(%

)

Drain Final Settling Tank

* Area Distribution representative of total particle size spectrum

“Selective Separation”

Baleen – the “missing link”

Micron Scale

Stage

Process

1000 100 10 1.0 0.1 0.01 0.001

Coarse Screening

Micro filtration

Ultra filtration

NanoFiltration

ReverseOsmosis

PrimarySecondary

Tertiary

10,000

Fine Screening

Baleen Filtration

The Baleen filter…

Modular design…

Baleen-Model

Industry-Application

’05 ’10 ’20 ’40 ’80 ‘160

Raw sewage influent (post grit screens) 10 35 100 200 400 800

Secondary effluent (post clarification) 15 50 150 300 600 1200

Stormwater run-off (post GPT) 20 70 200 400 800 1600

Baleen’s flow handling capability (kL/hr) within Municipal applications…

*Subject to site survey

The above tabulated performance figures refer to separation of visible, settle-able matter*

Baleen (inline micro-screening) Vs Settling (clarifier retention)

Objective: Separation of visible constituents from storm water influent

Flowrate (kL/hr)

Baleen

Model

Baleen

Volume(<150-micron)

Clarifier

Volume(<1hr-retention)

200 ‘20 32 m3* 260 m3**

1600 ‘160 135 m3* 2080 m3**

* Includes minimum working clearance

**Includes minimum civil clearance (1.3x)

Outcome: Baleen offers “absolute” retention to a given micron-rating