Electrochemical Process for
Sewage Treatment
CALVIN P.C. POON, Associate Professor
Department of Civil and Environmental Engineering
University of Rhode Island
Kingston, R. I. 02881
INTRODUCTION
Research on the control of undesirable aquatic growths has been influenced greatly be
Liebig's Law of the Minimum which can be described as "the variation in productivity of
land areas is most often determined by limitations imposed by the lack of some nutritional
element." Consequently, removing nutrients has been proposed by many to eliminate the
adverse effects of these contaminants. The need also arises from the fact that multiple reuse
of water in the United States will soon equal the recoverable stream flow and groundwater
supply. As the reuse of water becomes more prevalent, the problems of nutrient
overfertilization will continue to increase.
Since carbon is readily available in most waters as bicarbonates, nitrogen and
phosphorus have been chosen by most researchers as the nutrients to control. The
electrochemical process in the present study was used because of its high potential in
phosphorus and nitrogen removal. However findings in experiments have demonstrated its
equal effectiveness in BOD and suspended solids removal as well as its complete
disinfection of the treated wastewater.
The electrochemical process in this study is similar to that used by F6yn (I) to provide
an effective and inexpensive method for nitrogen and phosphorus removal from domestic
wastewater using sea water as the electrolyte. The purpose of the study is to investigate the
mechanism of nitrogen and phosphorus removal for developing a better understanding and
control of the process. Also the process is investigated as a means of total treatment of
wastewater including primary, secondary and tertiary treatment in one single step.
PROCESS DESCRIPTION
Early development of electrolyte sewage treatment has a primary interest in generating
chlorine for deodorizing and disinfecting wastewater. Eugene Hermite (2), as early as 1887,
has described a method of treating sewage by mixing it with a proportion of seawater and
electrolysing. He found, in addition to deodorizing and disinfecting effects, that Mg(OH)2
was produced as a powerful flocculent in the process which helped to bring down sewage
solids effectively. Not too long later, in 1890, a sewage treatment plant was installed in
London using what was known at that time as the Webster process (2). Iron went into
sewage from insulated iron plates comprising the electrodes to form ferric hydroxide which
caused rapid precipitation of sewage sludge and deodorization of wastewater. This same
principal was employed by General Electric in their electro-coagulation process as a part of
their shipboard waste treatment system (3).
Foyn intended to use a similar process to electrolyse a seawater-sewage mixture to
remove phosphates from sewage entering Oslo, Norway. His pilot plant study (1) showed 80
percent phosphates removal and 76-83 percent ammonia nitrogen removal. Significant
removal of BOD and decreases in turbidity were also reported. Mendia in Italy (2) modified
Foyn's process to treat a strong sewage. Clarifiers were used in conjunction with the
electrolytic cells for better sewage solid removal. An average of 58 percent BOD removal
was observed in the pilot study. Because the raw sewage contained very high BOD, much of
it remained in the effluent being discharged. The ability of the process in BOD removal
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