NUTRIENTS AND CHEMICAL OXYGEN DEMAND (COD) REMOVALS BY MICROALGAE-BACTERIA CO-CULTURE SYSTEM IN PALM OIL MILL EFFLUENT (POME)

Abstract

In Malaysia, large amounts of waste known as palm oil mill effluent (POME) are generated during the production process of crude palm oil. Conventionally, POME is treated using biological treatment that involves two processes; aerobic and anaerobic. These processes however, require long hydraulic retention time and produce methane and carbon dioxide (CO₂) that can cause environmental problems. Alternatively, POME can be treated by a combination of microalgae and bacterial co-culture that requires a shorter treatment time and is environmentally friendly. In this study, a microalgae strain, Chlorella vulgaris was co-cultured with a bacteria strain Azospirillum brasilense in POME with an initial concentration of 1.9´10⁶ cells/mL and 10⁴ CFU/mL, respectively. The removal of chemical oxygen demand (COD) and nutrients (phosphorus and ammonium) were analyzed using Standard Methods, APHA 1999. The effectiveness of the co-culture system in POME treatment under agitation and aeration conditions for nutrients and COD removals were studied. Results show that the removal of ammonium by microalgae was much higher under the aeration condition (73.5%) compared to that of the agitation condition (34.4%) in POME. Moreover, co-culture system exhibits better removal of ammonium, phosphorus, and COD (84%, 87.3% and 51.8%, respectively) compared to that in an axenic microalgae system (67%, 84.2% and 41.1%, respectively). The kinetic studies on the co-culture system and the nutrients removal were also conducted. The kinetic coefficients of maximum specific growth rate (µ_max) and half-saturation coefficient (k_s) obtained from Lineweaver-Burk plot were 0.192 d^?1 and 27.32 mg/L, respectively. Based on the findings obtained, the co-culture system could be implemented as an efficient and inexpensive alternative method for POME treatment.

ABSTRACT: Di Malaysia, banyak bahan buangan kilang minyak kelapa sawit yang dikenali sebagai (POME) telah terhasil ketika proses penghasilan minyak kelapa sawit mentah. Dahulu, POME dirawat menggunakan rawatan biologi yang terdiri daripada dua proses; erob dan anaerob. Walau bagaimanapun, proses-proses ini memerlukan masa yang panjang bagi pengekalan hidraulik dan gas metana dan karbon dioksida (CO₂) telah terhasil yang menyebabkan masalah alam. Sebagai alternatif, POME dapat dirawat dengan kombinasi mikroalga dan sistem bakteria ko-kultur melalui masa rawatan yang lebih pendek dan mesra alam. Kajian ini, strain mikroalga, Chlorella vulgaris telah di ko-kultur dengan strain bakteria Azospirillum brasilense dalam POME dengan ketumpatan awal 1.9´10⁶ sel/mL dan 10⁴ CFU/mL masing-masing. Penyingkiran kehendak oksigen secara kimia (COD) dan nutrisi (fosferus dan ammonium) telah dikaji menggunakan Kaedah Biasa, APHA 1999. Keberkesanan system ko-kultur dalam rawatan POME di bawah keadaan kisaran dan pengudaraan bagi nutrisi dan penyingkiran COD telah diselidiki. Dapatan kajian menunjukkan penyingkiran ammonium menggunakan mikroalga lebih banyak melalui keadaan pengudaraan (73.5%) berbanding keadaan kisaran (34.4%) dalam POME. Tambahan, system ko-kultur menunjukkan lebih bagus dalam penyingkiran ammonium, fosferus dan COD (84%, 87.3% dan 51.8%, masing-masing) dibandingkan dengan sistem mikroalga aksenik (67%, 84.2% dan 41.1%, masing-masing). Kajian kinetik pada sistem ko-kultur dan penyingkiran nutrisi turut dijalankan. Pekali kinetik kadar maksimum pertumbuhan sebenar (µ_max) dan pekali separuh-penepuan (k_s) telah diperolehi melalui plot Lineweaver-Burk iaitu 0.192 d^?1 dan 27.32 mg/L, masing-masing. Berdasarkan penemuan ini, sistem ko-kultur boleh dijalankan dengan cekap dan murah sebagai pilihan alternatif kepada rawatan POME.