Bio-Adsorption Pretreatment of Post Hydrothermal Liquefaction Wastewater (Phww) for Methane Production

Abstract

There are currently several promising technologies for the removal of toxic compounds from effluents; most of them are expensive. In the present investigation, peanut shells ( Arachis hypogaea ) were used as novel low-cost bio adsorbent in native (PB) and chemically modified (APB) for COD and NH 4 + removal from post-hydrothermal liquefaction wastewater (PHWW), which was subsequently submitted to anaerobic digestion. NaOH and HCl were used for APB activation. For comparison, granular activated carbon (GAC) was chosen as standard. The adsorbate-PHWW was obtained when 20% of solids (w/v) was used in the hydrothermal liquefaction (HTL) process carried out at 260°C for 60 min. The effect of various biosorption parameters such as temperature, pH and adsorbent dosage was studied and optimized using the response surface methodology (RSM). PB was shown to be more efficient in removing NH 4 + (Y 1 ), and higher COD removal percentages (Y 2 ) were achieved when using APB and GAC. After AD, the results showed that maximum COD removal were obtained for APB and PB pretreatment, respectively. Compared to untreated PHWW, the methane production rate was increased when bio adsorbents were used as pretreatment. These results showed the applicability of peanut shells as bio-adsorbents for PHWW pretreatment, which subsequently affected the biogas/methane yield.

Keywords: Bioadsorbents, Spirulina, methane production, Anaerobic digestion, Central composite design.