Sewage Treatment in Campus for Recycling Purpose: A Review
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60% (Kimura et al. 2009). Other consequences due to the fouling are lower permeate
flux, higher transmembrane pressure (TMP), and frequent membrane cleaning and
replacement (Mahendran et al. 2011).
However, membrane fouling can be reduced by pretreatment of feed, membrane
material/surface modification, and operating parameters (Zahrim et al. 2011). It is
reported that feed pretreatment such as coagulation–flocculation is the most successful and straightforward method to alleviate membrane fouling (Hilal et al. 2005; Lau
and Ismail 2009).
Dual—Membrane Filtration
Filtration using membrane filtration is a surface filtration device but different in terms
of size of the pores and filter medium. The size of pores for membrane ranging from
0.0001 to 1.0 µm used dual membrane filtration where ultrafiltration (UF) is conducted as pretreatment followed by reverse osmosis (RO) (Metcalf and Eddy 2003;
Zhang et al. 2010). Ultrafiltration usually removed macromolecules colloids, most
bacteria, some viruses, and proteins. Meanwhile, reverse osmosis can remove very
small molecules, color hardness, sulfates, nitrate, sodium, and other ions (Metcalf
and Eddy 2003).
UF processes predominantly use organic membranes, with cellulose acetate (CA),
polysulfone (PS), polyethylene (PE), polyethersulfone (PES) and polyvinylidene
difluoride (PVDF) in wastewater treatment (del Pino and Durham 1999). Reportedly
by Zhang et al. (2010), the PVC-UF membrane efficiently removed turbidity, suspended solids, and color, with removal efficiencies of 96.41%, 88.33%, and 50.00%,
respectively. Furthermore, the UF pretreatment was found to enhance the RO average
permeate flux and recovery by 34% and 21%, respectively, compared to the simulated conventional pretreatment system. However, the high levels of particulates,
dissolved organic matter (DOM) and microorganisms in wastewater can easily foul
UF membranes (Zhang et al. 2010).
CW Combined with Photocatalytic Ozonation
CW can also be coupled with other type of treatment to treat campus sewage. This
has been done by Horn et al. (2014) where CW was combined with photocatalytic
ozonation reactor (POR). Photocatalytic ozonation (PO) is an advanced oxidation
treatment which is also a combination of ozonation and photocatalysis process that is
objected to produce more hydroxyl radicals (OH·) by using high oxidation property of
ozone. Oxygen atoms of ozone will be reduced in the conduction band to ozonide ion
radicals (O3 .− ) that rapidly can be converted to HO
· . High concentration of HO
· will
increase the contaminants oxidation rate and minimize the potential of undesirable
recombination reaction of electrons as well as positive holes in the valence band,
which can result inhibition of the oxidation rate. However, CW coupled with POR
has lower COD removal compared to CW with subsurface infiltration by 25.4%.
227
60% (Kimura et al. 2009). Other consequences due to the fouling are lower permeate
flux, higher transmembrane pressure (TMP), and frequent membrane cleaning and
replacement (Mahendran et al. 2011).
However, membrane fouling can be reduced by pretreatment of feed, membrane
material/surface modification, and operating parameters (Zahrim et al. 2011). It is
reported that feed pretreatment such as coagulation–flocculation is the most successful and straightforward method to alleviate membrane fouling (Hilal et al. 2005; Lau
and Ismail 2009).
Dual—Membrane Filtration
Filtration using membrane filtration is a surface filtration device but different in terms
of size of the pores and filter medium. The size of pores for membrane ranging from
0.0001 to 1.0 µm used dual membrane filtration where ultrafiltration (UF) is conducted as pretreatment followed by reverse osmosis (RO) (Metcalf and Eddy 2003;
Zhang et al. 2010). Ultrafiltration usually removed macromolecules colloids, most
bacteria, some viruses, and proteins. Meanwhile, reverse osmosis can remove very
small molecules, color hardness, sulfates, nitrate, sodium, and other ions (Metcalf
and Eddy 2003).
UF processes predominantly use organic membranes, with cellulose acetate (CA),
polysulfone (PS), polyethylene (PE), polyethersulfone (PES) and polyvinylidene
difluoride (PVDF) in wastewater treatment (del Pino and Durham 1999). Reportedly
by Zhang et al. (2010), the PVC-UF membrane efficiently removed turbidity, suspended solids, and color, with removal efficiencies of 96.41%, 88.33%, and 50.00%,
respectively. Furthermore, the UF pretreatment was found to enhance the RO average
permeate flux and recovery by 34% and 21%, respectively, compared to the simulated conventional pretreatment system. However, the high levels of particulates,
dissolved organic matter (DOM) and microorganisms in wastewater can easily foul
UF membranes (Zhang et al. 2010).
CW Combined with Photocatalytic Ozonation
CW can also be coupled with other type of treatment to treat campus sewage. This
has been done by Horn et al. (2014) where CW was combined with photocatalytic
ozonation reactor (POR). Photocatalytic ozonation (PO) is an advanced oxidation
treatment which is also a combination of ozonation and photocatalysis process that is
objected to produce more hydroxyl radicals (OH·) by using high oxidation property of
ozone. Oxygen atoms of ozone will be reduced in the conduction band to ozonide ion
radicals (O3 .− ) that rapidly can be converted to HO
· . High concentration of HO
· will
increase the contaminants oxidation rate and minimize the potential of undesirable
recombination reaction of electrons as well as positive holes in the valence band,
which can result inhibition of the oxidation rate. However, CW coupled with POR
has lower COD removal compared to CW with subsurface infiltration by 25.4%.