The Removal of Heavy Metals from the Leachate of Aged Landfill: The Application of the Fenton Process and Nanosilica Absorbent

Since leachate is typically composed of numerous constituents, its management requires special attention. After the raw leachate of Saravan in Rasht (Guilan Province, Iran) was transferred to a laboratory and its specifications were determined, it was subjected to experiments by the bench-scale method. The analyses of pH and heavy metals were performed in the main and control anaerobic reactors at time zero, before precipitation, and two hours after precipitation. After the anaerobic process was over and the optimal retention time was identified in the anaerobic reactor, the removal of heavy metals was analyzed by the Fenton process and nanosilica absorbent in leachate treatment. In the primary anaerobic reactor, the highest and lowest removal rates were 59 and 39% for Ni and Cu, respectively. In the Fenton process with optimal H2O2/Fe+2 ratio, Cu and Hg showed the lowest and highest removal rates of 22.4 and 54.54%, respectively. At the optimal rate of nanosilica absorbent and the retention time of 15 min, As was removed maximally with an efficiency of 38% and Cu was removed minimally. The results revealed that the integration of the anaerobic process with the Fenton process and nanosilica absorbent was very effective in removing heavy metals from the aged landfill leachate.

Anaerobic Mesophilic Co-Digestion of Swine Slurry and Hidrolyzate in Batch Reactors: A Case Study

The management of residual flows from swine farms, such as slurry and hydrolyzate, is a serious environmental problem in Portugal, so the search for new solutions is important, especially if they can be implemented in production sites, avoiding the transport of waste. Anaerobic co-digestion can configure a sustainable method of management and valorization of these flows in swine farms, resulting in biogas to produce energy and a digestate with agronomic value. The swine hydrolyzate is the product from the elimination of swine carcasses on the farms, through a hydrolysis process. Its use in the anaerobic process wasn’t found in the literature, identifying the need to evaluate its potential. Thus, anaerobic co-digestion of swine slurry and hydrolyzate was carried out and the main purpose of this research was to find the best feeding ratio between the two substrates in batch test, focusing on biogas production. The study was developed in two phases, both under mesophilic conditions. In the first one, using 100 ml syringes, the effect of the relative proportion of substrates on the anaerobic co-digestion potential was investigated and the effect of pressure sterilization of the substrates on biogas production was verified. In the second phase, a larger scale study was carried out in a 4,500 ml digestor, ran under the conditions identified as the most favorable in the preliminary tests. The results obtained allowed us to conclude that the largest volume of accumulated biogas was obtained with the proportion of 90.9% swine slurry: 9.1% swine hydrolyzate (v/v); and that the sterilization of the substrates doesn’t constitute an effective thermal pre-treatment. The larger scale test revealed an inefficient anaerobic process due to the inhibitory effect caused by the accumulation of ammonia and volatile organic acids. However, the production yield was 606.8 LBiogas/kgVS and 431.6 LMethane/kgVS, indicating that process allowed a production of biogas and methane higher than the values cited in literature for anaerobic digestion of swine slurry. This result showed that the use of swine hydrolyzate as a co-substrate results in a better balance of nutrients, promoting a better development of microorganisms.

Reduksi Bahan Organik Kulit Kopi dan Eceng Gondok Terhidrolisis Menggunakan Proses Anaerbik

Coffee pulp and water hyacinth are a biomass source that can be used to feeding material for biogas production as energy an anaerobic digester. But coffee pulp and water hyacinth contain lignin. The Alkaline or base hydrolysis is a method of the solving chemical structure of lignin compounds using a strong acid and base. The focus of research investigated the base hydrolysis with NaOH in coffee pulp and water hyacinth an anaerobic process for organic material reduction. The research design in laboratory conduct of organic materials reduction on coffee pulp and water hyacinth used Completely Random Design (CRD). Anaerobic treatments were without hydrolysis (H1), only the coffee pulp with hydrolysis (H2), only water hyacinth with hydrolysis (H3) and all with hydrolysis (H4). The highest NaOH concentration for lignin reduction on the base hydrolysis was 60 ppm. The analysis of variants with significantly (p<0.05) showed all treated differently. Anerobic treatment of the coffee pulp and water hyacinth (H4) had the highest value organic material reduction. The efficiency of organic material reduction i.e. C/N, BOD and COD was in sequence namely 64.22 ± 0.02; 75.23 ± 0.02 dan 52.55 ± 0.04.

Anaerobic Degradation of Individual Components from 5-Hydroxymethylfurfural Process-Wastewater in Continuously Operated Fixed Bed Reactors

Production of bio-based materials in biorefineries is coupled with the generation of organic-rich process-wastewater that requires further management. Anaerobic technologies can be employed as a tool for the rectification of such hazardous by-products. Therefore, 5-hydroxymethylfurfural process-wastewater and its components were investigated for their biodegradability in a continuous anaerobic process. The test components included 5-hydroxymethylfurfural, furfural, levulinic acid, and the full process-wastewater. Each component was injected individually into a continuously operating anaerobic filter at a concentration of 0.5 gCOD. On the basis of large discrepancies within the replicates for each component, we classified their degradation into the categories of “delayed”, “retarded”, and “inhibitory”. Inhibitory represented the replicates for all the test components that hampered the process. For the retarded degradation, their mean methane yield per 0.5 gCOD was between 21.31 ± 13.04 mL and 28.98 ± 25.38 mL. Delayed digestion was considered adequate for further assessments in which the order of conversion to methane according to specific methane yield for each component from highest to lowest was as follows: levulinic acid > furfural > 5-hydroxymethylfurfural > process-wastewater. Disparities and inconsistencies in the degradation of process-wastewater and its components can compromise process stability as a whole. Hence, the provision of energy with such feedstock is questionable.