Wastewater Byproducts Thermal Integration

Biosolids, biogas and hydrogen sulfide (H₂S) are byproducts of wastewater plants constantly increasing with growing population. Traditional disposal of biosolids by landfilling, biogas flaring and H₂S treatment is not integrated. This treatment approach leads to substantial greenhouse gas emissions, up to 54% of total waste industry emissions. It also represents high operating costs for wastewater plants. Only biosolids handling represents between 45% and 65% of wastewater treatment plants operating expenses. The feasibility of obtaining porous media from biosolids for hydrogen sulfide treatment using biogas energy was studied. Literature regarding wastewater byproducts integrated treatment is scarce, and the required data to evaluate the feasibility of byproducts integration is site specific, and is not yet available for treatment plants in Abu Dhabi. Biosolids samples and biogas composition data were obtained from a municipal wastewater treatment plant in Abu Dhabi. Biosolids chemical and physical properties to assess the potential for H₂S treatment were measured. Literature was reviewed to select biosolids pyrolysis conditions to obtain high porous-surface-areas chars. Experimental pyrolysis was conducted on a Differential Scanning Calorimeter (DSC) measuring the thermal process energy consumption. Biogas energy was estimated from thermodynamic analysis and compared with the biosolids pyrolysis process energy consumption. It was found that biosolids chars surface area (108m²/g) is comparable with commercial activated carbons for H₂S treatment and have an estimate of 11% CaCO₃ which can potentially react with H₂S. Energy consumption of the biosolids pyrolysis process is only 4% of the available biogas energy in the plant.