Biological activities in the activated sludge system are
sensitive to environmental factors such as temperature, pH,
dissolved oxygen and feed conductivity. The effect of salt on
nitrification/denitrification process is a major concern in
recent years. Saline wastewater are usually treated through
physico-chemical means, as conventional biological
treatment is known to be strongly inhibited by salt (mainly
NaCl). However, physicochemical techniques are
energy-consuming and their startup and running costs are high.
Nowadays, alternative systems for the removal of organic
matter are studied, most of them involving anaerobic or
aerobic biological treatment [1]. Previous studies indicated
that high salinity adversely effects the reduction of chemical
oxygen demand (COD) in normal wastewater plants of
activated sludge [2], [3]. However, the adaptation of biomass
to saline wastewater improved COD reduction [4], [5].
Another study indicated that nitrogen reduction is
insignificantly effected up to a salt level of 4000 mg/l just
little above 10% of salt concentration in normal seawater.
Even at this low level of salt however, phosphorus reduction
dropped from normal reduction of 82% to only 25% showing
severe interference of salt [6]. Concerning nitrogen, a similar
study reported that in low salt concentration, ammonia
reduction can be achieved within the range of 20 to 50% [7].
Past records of studies with highly saline wastewater from
seafood industry and RO or other membrane processes
treating wastewater effluent are inadequate to draw any
conclusive inference on the treat-ability of saline wastewater.
In such water, high levels of nutrients (nitrogen ranging of
50-60 mg/L and phosphorus ranging10-12 mg/L) are common
features. A recent sequential batch reactor (SBR) study
concentrated on nutrient reduction from saline wastewater
(artificial seafood processing wastewater). The wastewater
was prepared to have the approximate concentrations of total
COD 1000 mg/L, soluble COD 500 mg/L, TKN 120 mg/L,
PO-P 20 mg/l [8]. In this study 80-92% organics and nitrogen
reduction was reported and also found that after the influent
was modified with acetate addition, satisfactory phosphorus
reduction was also achieved within 2-3 d [8]. The author
reported nutrient reduction efficiency in sequential
bio-reactors with variable hydraulic retention time. Best
removal rate was recorded at 24 h hydraulic retention and 12
days sludge age. The author reported that better result is
accomplished from the acclimatization of bacteria at higher
salinity as reported by others [4], [5].