Wastewater byproducts thermal integration

Abstract

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 are 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. It is also one of the goals of Abu Dhabi Vision 2030 to divert 85% of waste out of landfills, however, disposal of biosolids on landfills is still dominant on the Emirate and at a worldwide scale biosolids beneficial use is low in most regions. Literature on integrated byproducts treatment methodologies combining, biogas, biosolids and hydrogen sulfide is scarce. On the other hand, the feasibility of such methodologies strongly depends on the composition of each byproduct, which is sitespecific. Biosolids samples and biogas composition data were obtained from a municipal wastewater treatment plant 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 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 char 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. However, constraints set by legal emissions regulations on heavy metals were identified, limiting the conversion capacity from full processing of 32 ton biosolids/day. to 1.15 ton biosolids/day.

Date of Award	May 2017
Original language	American English