4. Conclusions
Current microalgal biofuel production relying on suspended
algal culture has been limited by its high operating costs associated
with costs for substrate/nutrients, low productivity of algal biomass,
and high energy-consuming harvest of algal cells. Various
types of algal biofilm reactors integrated with wastewater treatment
were developed to overcome current limitation of algal biofuel
production. To date the horizontal, vertical, flow cell, and
rotating biofilm reactors have been studied to produce algal biomass
for biofuel and remove nutrients from wastewater. However,
the rotating biofilm reactor among various types of biofilm reactors
was found to be a promising option to provide high biomass
productivity and efficient utilization of nutrients in wastewater.
Although a variety of materials have been used as the supports
for algal biofilm, stainless steel, nylon and natural fibers were
found to be highly effective support materials for microalgal biofilm.
So far the integration of algal bioreactor and wastewater
has been limited to municipal wastewater while a few agricultural
wastewater have been used for algal bioreactors due to inhibition
of algal growth with high ammonium concentrations and poor
light delivery with high turbidity of animal manure. To enhance
the algal biomass production using animal wastewater, dilution
of the swine and dairy manure wastewater with municipal
wastewater or seawater was also studied. Overall, algal biofilm
reactors integrated with wastewater would have high potential
for high productivity of algal biomass for biofuel and efficient
wastewater treatment if various conditions are optimized.