Cultivation of Green Algae Chlorella sp. in Different Wastewaters from Municipal Wastewater

Abstract The objective of this study was to evaluate the growth of green algae Chlorella sp. on wastewaters sampled from four different points of the treatment process flow of a local municipal wastewater treatment plant (MWTP) and how well the algal growth removed nitrogen, phosphorus, chemical oxygen demand (COD), and metal ions from the wastewaters. The four wastewaters were wastewater before primary settling (#1 wastewater), wastewater after primary settling (#2 wastewater), wastewater after activated sludge tank (#3 wastewater), and centrate (#4 wastewater), which is the wastewater generated in sludge centrifuge. The average specific growth rates in the exponential period were 0.412, 0.429, 0.343, and 0.948 day−1 for wastewaters #1, #2, #3, and #4, respectively. The removal rates of NH4–N were 82.4%, 74.7%, and 78.3 % for wastewaters #1, #2, and #4, respectively. For #3 wastewater, 62.5 % of NO3–N, the major inorganic nitrogen form, was removed with 6.3-fold of NO2–N generated. From wastewaters #1, #2, and #4, 83.2%, 90.6%, and 85.6 % phosphorus and 50.9%, 56.5%, and 83.0 % COD were removed, respectively. Only 4.7 % was removed in #3 wastewater and the COD in #3 wastewater increased slightly after algal growth, probably due to the excretion of smal