ASSESSING THE EFFICIENCY OF BAMBOO-BASED ACTIVATED CARBON AS A LOW-COST WASTEWATER TREATMENT OPTION

Abstract

Wastewater treatment has become a global phenomenon because of the numerous benefits associated with its reuse due to burgeoning global population that is putting huge pressure on freshwater supplies. Several of the known treatment procedures and materials are labourious, expensive, sophisticated and sometimes realistically unachievable. It is in the light of the above that an assessment was made of activated carbon produced from bamboo as a viable low-cost treatment option. The activated carbon was produced from freshly harvested matured bamboo stalks (bambusa vulgaris) through carbonization and activation processes using trioxonitrate (V) acid (HNO3) and potassium hydroxide (KOH) as activating agents. The produced activated carbon was characterized using fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) technologies and later introduced to treat aquaculture wastewater obtained from one of the fish ponds at Teaching and Research farm (T &R) of the Federal University of Technology, Akure. Initial and final characterization of the wastewater samples were performed with seventeen physico-chemicals, seven heavy metals, and two microbiological parameters. The physico-chemical parameters are pH, electrical conductivity (EC), chloride, total hardness, Calcium hardness, Magnesium hardness, Alkalinity and Acidity. Others are Total Dissolved Solid (TDS), nitrate, nitrite, sulphate, dissolved oxygen (DO) and biological oxygen demand (BOD5). The rest are total suspended solid (TSS), total solid (TS) and turbidity. For the heavy metals, chromium (Cr), copper (Cu), iron (Fe), cadmium (Cd), lead (Pb), zinc (Zn) and nickel (Ni) while the two microbial analysis are total coliform and total viable counts of Bacteria, Yeast and Fungi. These analyses were performed in accordance with the America Public Health Association (APHA) procedure while the treatment was carried out using a fixed bed adsorption column at the Chemistry laboratory of the University and the experimental design comprised of three treatments 3 and three replicates. The results obtained were subjected to statistical analyses using tools such as Least Square Significant Difference (LSD) and Duncan Multiple range test at 95% level of significance. Removal efficiencies among all treatments were also determined while model adsorption best fit using Adam-Bohart, Yoon-Nelson and Thomas models were performed on nitrate, nitrite and turbidity. From the SEM imagery, of all the activated carbon produced, KOH activated carbon at 1500x magnification had largest and most well-developed pore spaces that has maximum capacity to absorb contaminants from wastewater when compared with both HNO3 activated carbon and carbonated charcoal. Similar results was recorded at the FTIR analysis showing highest amount of functional groups on its surface when compared with carbonated charcoal and HNO3 activated carbon. The removal efficiency between initial and final characterization of the physico-chemical parameters with the adsorbents were marginal with the exception of calcium hardness and acidity having 61 % and 62 % respectively in carbonated charcoal. Acidity, nitrate and sulphate have 62 %, 58 % and 57 % respectively in HNO3 activated carbon and with KOH activated carbon, acidity and nitrite have 60 % and 75 % respectively. As for the heavy metals, only Cd and Pb had 79 % and 77 % removal efficiencies using carbonated charcoal, Pb (100 %), Zn (87 %) and Ni (67 %) in HNO3 activated carbon while all the heavy metals experienced considerable removal efficiency ranging from 71-100 % in KOH activated carbon. Correlation coefficients ranging from 79 % through 99 % were recorded in all the treatment for Nitrate, Nitrite and Turbidity using Adam-Bohart, Yoon-Nelson and Thomas adsorption models except for turbidity with carbonated charcoal treatment having correlation coefficient less than 50 %. This study therefore highlights the efficacy of HNO3 and KOH activated carbon when compared with carbonated charcoal in treating aquaculture wastewater effectively. However, KOH activated carbon is established to be more effective in heavy metal removal from the wastewater due to its widespread pore spaces and deeper cavities depicting very good surface for adsorption capacity.