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15 Photobiological Reactors for the Degradation of Harmful Compounds in Wastewaters

the degradation in bioreactor. This study demonstrates the useful photo-Fenton

pretreatment of an aromatic p-NTS prior to the biotreatment with a tandem reactor

concept. The main parameters affecting the performance of the photo-assisted

reactor have been reported in this study. In the first stage, the reactor was affected

by the amount of substrate, oxidant, and the flow rate. This study concentrated on

Fenton treatment under illumination since dark reactions using the Fenton reagent

were shown to be slow and inefficient. The fixed biomass in the bioreactor resisted

the variations of substrate concentrations and flow rate over long periods (up to

two months). The reactor could be operated within this period from a low concen-

tration (40 ppm) to a high concentration (1000 ppm) of substrate without altering

the overall performance of the system. Biolite was a cheap support and allowed an

adequate contact during the recirculation in the bioreactor. No appreciable increase

in the biomass volume was observed during operation within a period of a week.

Toxic intermediate products did not develop during degradation in the solution as

revealed by toxicity test. In spite of the initial photoreactor treatment and beneficial

reduction of C in the biological second stage, no full mineralization was observed.

It seems that one part of the C intermediates degrades easily, but another part that

even lacking aromatic character does not undergo easy biodegradation in the second

stage. Fixed biomass bioreactors take less space (up to 10 times) than more conven-

tional reactors using suspended biomass [20].

Anaerobic Sludge Reactor (Photocatalytic Treatment) Hostile retting-pond wastewater

was treated by anaerobic and photocatalytic process for phenol removal. In recent

study, upflow anaerobic sludge blanket reactor was used over a period of 164 days

at pH 3, 5, 7, and 9 with HRT from 35 to 20 hours. Anaerobic reactor showed COD

and phenol removal of 85% and 75% respectively at pH of 7.0 and HRT of 25 hours.

Research surface methodology (RSM) and regression quadratic model were used for

COD removal. Photocatalytic process was industrialized by one-way analysis of vari-

ance (ANOVA). The joint anaerobic and photocatalytic treatment showed 95% and

93% COD and phenol removal respectively. The anaerobic treatment was performed

in upflow anaerobic sludge blanket reactor (UASBR) at 25 hours HRT and 3, 5, 7,

or 9 pH, which shows 41%, 55%, 85%, and 80% of COD removal and 56%, 60%, 77%,

and 64% of phenol removal respectively. Photocatalytic process was used to treat

further primary treated wastewater at pH of 7.0. Through RSM, the best treatment

conditions have been found to be 3 g/l Fenton and 20 ml H2O2 with 30 minutes reac-

tion time. The UASBR with photocatalytic treatment led to total COD and phenol

elimination efficiencies of 95% and 93% respectively [21].

Hybrid Reactor (Dark Photo-Fermentative Hydrogen Production) The study inspected the

potential of consecutive dark and photo-fermentation for wastewater treatment and

concurrent bio-hydrogen production. To this end, a new shape, namely dark-photo

circular puzzled reactor (DP-CBR) was obtainable, which works at ambient temper-

ature (21 ± 10 ^∘C). The reactor was comprised of four identical compartments, where

fluorescent tubes were connected to the last two compartments, i.e. C1–C2 (dark)