Biochemical Potential Research Articles

Preparation and testing of low-cost bioadsorbents for improving the anaerobic digestion of post-hydrothermal liquefaction wastewater (PHWW)

There are currently several promising technologies for the removal of toxic compounds from wastewater; most of them are expensive or require sophisticated equipment. Thus, this study proposes that peanut shells be used as low-cost bioadsorbents for the removal of organic matter (COD) and ammoniacal nitrogen (NH4+-N) from Spirulina hydrothermal liquefaction wastewater (PHWW). Additionally, anaerobic digestion (AD) was used as a biological treatment for pretreated PHWW (by adsorption) to promote additional organic matter removal while recovering energy in the form of methane. In this way, native (PB) and modified (APB) forms of peanut shell bioadsorbents were investigated. APB was activated using NaOH and HCl. For comparison, granular activated carbon (GAC) was chosen as the standard. The adsorbate-PHWW was obtained by using 20% solids (w/v) in the hydrothermal liquefaction (HTL) of Spirulina at 260 °C for 60 min. Response surface methodology (RSM) was used to explore and optimize the effect of various adsorption parameters, such as temperature, pH, and adsorbent dosage. Biochemical potential (BMP) tests were conducted under mesophilic conditions. In adsorption assays, PB was found to be more efficient at removing NH4+-N, while APB and GAC achieve higher COD removal percentages. In comparison to untreated PHWW, bioadsorption promoted higher efficiency phenol removal and COD conversion to methane during BMP tests. The anaerobic processes that followed APB and PB adsorption significantly removed more COD than the process fed with GAC-pretreated PHWW. These results established the feasibility of using peanut shells as bioadsorbents in the pretreatment of PHWW, which resulted in an increase in biogas/methane yield.

Start-Up Strategy and Process Performance of Semi-Continuous Anaerobic Digestion of Raw Sugarcane Vinasse

The sugarcane distillery waste water is generated throughout the sugarcane molasses fermentation and distillation. In Reunion Island, a part of the vinasse production is treated by methanisation process. However, the remaining part is diluted then discharged into the sea. The aim of this work is to study the anaerobic treatment of sugar cane vinasse, with energy recovery. Nonetheless, vinasse pollutant load is difficult to treat. Regarding the experimentations, the biochemical potential (BMP) test is used for the determination of the methanogen potential. The BMP is then modelled with the modified Gompertz and the first order kinetic models. Furthermore, a laboratory study is carried out for studying the methane production of vinasse in semi-industrial scale over a period of 130 days. The start-up strategy of the 16 L pilot is proposed, in particular the gradual increase of organic load. The physico-chemical analysis of the medium is needed to prevent and explain the failure of the process. Indeed, the biogas production and physico-chemical measurements during the digestion are presented and discussed. The maximum methane yield of the BMP is 185 $${\text{NL}}_{{{\text{CH}}_{4} }} \,{\text{kg}}_{{{\text{COD}}}}^{ - 1} ,$$ obtained with I/S ratio in terms of volatile solids of 0.7. The outcomes showed that the first-order kinetic and modified Gompertz models fit well with the BMP test curves. Concerning the pilot, the start-up period lasted 45 days the maximum specific production was 151.00 $${\text{NL}}_{{{\text{CH}}_{4} }} \,{\text{kg}}_{{{\text{COD}}}}^{ - 1}$$ (232.31 $${\text{NL}}_{{{\text{biogas}}}} \,{\text{kg}}_{{{\text{COD}}}}^{ - 1}$$ ). In further studies, different mixing strategies will be studied.

Improvement of anaerobic digestion of swine slurry by steam explosion and chemical pretreatment application. Assessment based on kinetic analysis

Swine slurry is generated in large quantities and anaerobic digestion may represent an appropriate process to both treat and revalue this waste as an energy source. Pretreatment processes aim to increase the anaerobic biodegradability of a specific waste. In this study, steam explosion and weak thermal-alkali pretreatments are evaluated. The first series of Biochemical potential (BMP) test is set to establish the best substrate/inoculum ratio conditions, and then other tests are carried out to assess the impact of these pretreatments on the methane potential and maximum production rate by using the modified Gompertz equation. The S/I ratio exerts an influence on the BMP results and the optimum ratio was found to be between 0.1–0.25gVSsgVSI−1. Steam explosion leads to an improvement of both the methane potential and the maximum production rate at the highest severity conditions. Weak alkali thermal pretreatment improved the maximum production rate but affected negatively the methane potential of the substrate.