Hybrid Anaerobic Reactors

Simultaneous removal of trichlorfon, with glucose added as carbon source for degradation requirement of trichlorfon in a hybrid bioreactor was modeled (Chen et al., 1998). The hybrid bioreactor has both suspended biomass and magnetically immobilized biofim. Evaluation of the respective roles of these two types of biomass with a mathematical model was developed and the model also verified well with experimental results. It has been found that the suspended biomass plays a key role in removing both substances in the system. This was due to complete coexistence of both trichlorfon-degrading and glucose-removing bacteria completely in each type of the granules. Such a system is applicable to the treatment of complex industrial wastewaters that contain easily biodegradable organics as well as refractory pollutants.

The use of an upflow anaerobic hybrid blanket (UAHB) reactor, adding water absorbing polymer particles (WAP), to treat a fermentation process wastewater consisting of high sulfate and ammonia, is proven to have a better stability (Imai et al., 1998). The granules were developed in the UAHB process, in which a filter was installed in the upper part of reactor and WAP were also added into inoculum, for treating sulfide- and ammonia-rich wastewater.

Anaerobic thermophilic (55°C) treatment of thermomechanical pulping whitewater (TMP) in reactors based on biomass attachment and entrapment was studied (Jahren et al., 1999) using three different reactor configurations. Up to 70% COD removals were achieved in all the reactors. The anaerobic hybrid reactor, composing a UASB and a filter, exhibited degradation rates up to 10 kg COD/m3-d. The anaerobic multistage reactor, consisting of three compartments, each packed with granular sludge and carrier elements, showed degradation rates up to 9 kg COD/m3-d. Clogging and short-circuiting eventually became a problem in the multistage reactor, probably caused by too high packing of the carriers. The anaerobic moving bed biofilm reactor performed similar to the other reactors at loading rates below 1.4 kg COD/m3-d, which was the highest loading rate applied. The use of carriers in the anaerobic reactors allowed short HRT with good treatment efficiencies for TMP whitewater.

Pentachlorophenol (PCP) is remarkably and efficiently degraded in a hybrid reactor supplied with a mixture of fatty acids (propionic, butyric, acetic, and lactic) and methanol (Montenegro et al., 2001). The reduction of COD was around 97% and methane was found to be 86% in the biogas production. The efficiency of (VFA) breakdown was 93, 64, and 74% respectively for butyric, propionic, and acetic. PCP total removal of more than 99% was reached by granular sludge activities formed during 21 months of reactor operation. Methanogenic microorganisms predominance was noticed with 105 to 106 cells/mL during enumeration on methanol or lactate added to sulfate culture media. The removal rate was 1.07 mg PCP ■ g-1 Volatile solid (VS) ■ d-1 during the highest PCP concentration addition.

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