(215f) An Integrated Solar Photocatalysis?Organic Membrane Separation and SBR Process for the Treatment of Pharmaceutical Wastewater

1.  Introduction

Due to strong oxidation
ability, no secondary pollution and mild reaction conditions ^[1], photocatalysis
treatment of pharmaceutical wastewater with refractory organic is becoming attractive
recently, and related research have been carried out widely. There is, however,
little information about the solar photocatalysis degradation of pharmaceutical
wastewater available, and the majority of published solar photocatalysis researches
are focused on the compound parabolic collector(CPC) reactor with immobilization
of TiO₂ on solid supports, which exists mass transfer limitation
compared with suspension photocatalytsis, to eliminate the
difficult separation and recycling of TiO₂.

Based on high separation
efficiency and easy operation for organic membrane separation, the paper
firstly introduced a novel type of three-phase fluidized bed equipment of solar photocatalysis-organic membrane separation (the equipment) which TiO₂can be recycled, then the combined
process of the equipment with SBR (Sequential Batch
Reactor) for pharmaceutical
wastewater treatment were investigated.

2.  Experimental

2.1  Introduction
of the equipment

The equipment
consists
of photocatalytic reaction zone (PRZ) and membrane separation zone (MSZ), which PRZ is comprised of bottom water-tank, casing tube reactor,
CPC, upper water-tank and PRZ aeration device, there also are wastewater inlet
and sludge outlet in bottom tank, UV lamp (main wavelength of 254 nm, power of 15 W)
which is set in the centre of tube reactor. MSZ is comprised of membrane separator shell, submerged
membrane module and MSZ aeration device. The water outlet is connected with membrane module. Membrane separator is connected
with upper and bottom water-tank by connecting pipe and circulating pipe with air rising jet, respectively. CPC and tube reactor were facing the equator with the certain angle to horizontal plane, which equals local
latitude.

Wastewater entering into bottom water-tank
rapidly mixes with TiO₂to form three phase fluidized bed under PRZ
aeration flow. When the wastewater,
containing air bubble and TiO₂, flows
through shell sides of tube
reactor, photocatalytic
degradation reaction happens under UV irradiation. Air bubbles escape out of the wastewater when degraded
wastewater flows into upper water-tank. Wastewater with only TiO₂ flow back bottom water-tank by circulating pipe again after they come into membrane
separator by connecting pipe. Obviously, the wastewater in the equipment is always in circulating flow state. TiO₂is intercepted when the wastewater in membrane separator
is passing through membrane module and the intercepted TiO₂flows back to
the bottom water-tank by circulating flow. Air rinsing makes deposited TiO₂ suspend again to keep TiO₂
suspension concentration invariable ^[2].

2.2  Experimental methods

The pharmaceutical wastewater was first pre-treated by flocculation with Poly Aluminium Chloride (PAC), and then the pre-treated wastewater obtained under the appropriate flocculation conditions was diluted 50 times and used to photocatalytic
degradation experiment. The photocatalyzed wastewater was also
treated by SBR under the aeration time
of 8 h, anaerobic stir of 5 h and hydraulicretention
time of 15 h.

3  Results
and Discussion

3.1  Pretreatment of pharmaceutical wastewater

After flocculation pre-treatment with PAC, the COD_Cr, chromaticity and turbidity of pharmaceutical wastewater decrease from
294500
mg/L, 4100, 95NTU to 266000
mg/L, 3150, 31NTU respectively, and the appropriate PAC dosage
is 400 mg/L. Although the photocatalytic degradation rate of the pre-treated wastewater always increases with its dilution ratio, the appropriate dilution ratio can be regarded
as 50 in the paper.

3.2 
Effect of solar UV intensity and UV light sources

The more the total UV
light intensity, whether under only solar or the double light sources of solar and UV lamp, the higher the photocatalytic degradation rate of the wastewater. Besides, there
is more obvious influence of UV lamp on the
increase of photocatalytic degradation rate under cloudy day than clear day, which indicates that
UV
lamp made the equipment still keep high degradation rate in cloudy day.

3.3  Effect of the wastewater
pH value

Generally, the photocatalytic degradation rate of the wastewater
increase with the decrease of the wastewater pH value. Nevertheless, the rate under
pH value of 3.0 is lower than that of 5.0. Therefore, the appropriate pH value
of the pharmaceutical wastewater is 5.0.

3.4  Photocatalytic processes comparison of
laden and commercial TiO₂

Air
rinsing makes TiO₂ deposited in recycle pipe suspend again to keep the suspension concentration of laden and commercial TiO₂ 0.715g/L, 0.710g/L respectively, which the concentrations of two kinds TiO₂ almost equal each other. However, the photocatalytic
degradation rate of laden TiO₂ for the wastewater
is obvious higher than that of commercial TiO₂.

3.5  Treatment by combined solar
photocatalysis and SBR process

After
single solar photocatalytic
degradation for 6 hours under cloud day, the B/C value of pharmaceutical
wastewater increases from 0.29 to 0.37, which indicates that biochemical degradability of the wastewater is improved evidently, and the COD_Cr, TOC, BOD₅ also decline greatly. In the SBR stage, the pollutants in the wastewater are removed further, and the SBR effluent
meets with the Second Chinese Effluent Standard. It is feasible to treat
pharmaceutical wastewater by combined solar photocatalysis - membrane
separation and SBR processes.

4
 Conclusion

Combined
process of solar photocatalysis-organic membrane separation and SBR can effectively treat pharmaceutical wastewater, and UV lamp in the equipment makes the combined
process still effectively work even in cloudy day.

Acknowledgements

This work was sponsored by Tianjin Research Program Key Projects of
Apply Base and Frontier technology (11JCZDJC24900) and Open Fund of State Key Laboratory of Hollow Fiber Membrane
Materials and Processes (201022).

Literature Cited

[1] Marcela
Boroski, Angela Claudia Rodrigues, Juliana Carla Garcia,Luiz Carlos Sampaio,
Jorge Nozaki1, Noboru Hioka. J
Hazardous Materials 162, 448 (2009)

[2] CHANG Qing, XIE Liping,
FEI Xuening, DAI Xiaohong, JIANG Yuanguang. J Sichuan
University(Engineering Science Edition) 44, 249 (2012)