69    COST-EFFECTIVE TREATMENT BY AERATED POND
CHEMICAL CLARIFICATION AND A WATER
COOLING SYSTEM RECYCLING EFFLUENT
AS MAKE-UP
Noah Galil, Senior Lecturer
Yael Levinsky, Research Engineer
Menahem Rebhun, Professor
Faculty of Civil Engineering
Technion-Israel Institute of Technology
Haifa 32000, Israel
INTRODUCTION
The study is based on the performance of a full scale industrial system, treating wastewater from a
petrochemical complex. The final effluent quality requirements were determined by the fact that the
effluent has to be recycled as make-up to the local water cooling system, replacing fresh water.
At the primary stages, the treatment includes separation of "free" oil by API type separators and
removal of emulsified oil by chemical flocculation and dissolved air flotation (DAF). After these
stages of treatment, the effluent contains up to 50 mg/L oil, 500 mg/L COD, 220 mg/L BOD, 11
mg/L phenols and 16 mg/L ammonia as nitrogen (Table I). For improving the effluent quality a
biological treatment process is necessary and for this purpose three alternatives have been studied and
discussed by the authors: activated sludge, RBC and aerated ponds.1"3
Experimental results, based on pilot plant studies showed that activated sludge and RBC could
provide efficient removals of biodegradable organic matter and nitrification; however, two major
disadvantages have been reported: (a) both processes and especially the activated sludge, were sensitive to external disturbances, such as uncontrollable loads of pollutants, causing unstable effluent
quality; (b) the capital investment was estimated as close to 6 million US dollars for each one of these
processes and this was considered as too high by the management of the industrial complex.
Table I.    Effluent Quality After Different Treatment Stages
Influent3
Combined Biotreatment
Constituent
Aerated
Ponds
Lime
Clarific.
WCS
Blow
Downb
Suspended Solids
Total
69
123
49
48
32
Ammonia as N
16
10
8.3
0.9
0.9
Hydrocarbons
48
26
3.6
4.8
2.5
COD
Total
Soluble
486
380
272
130
88
75
96
87
80
68
BOD
Total
Soluble
220
160
85
31
15
6
16
6
6
<5
Phenols
11
0.1
0.1
<0.1
<0.1
a After treatment
b After additional
by API and DAF.
treatment by lime clarification.
48th Purdue Industrial Waste Conference Proceedings, 1993 Lewis Publishers, Chelsea, Michigan 48118. Printed in
U.S.A.
691