A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item EFFECTS OF FULL-SCALE THERMAL HYDROLYSIS-ANAEROBIC DIGESTION ON THE TEMPORAL TRENDS OF POLYBROMINATED DIPHENYL ETHERS IN BIOSOLIDS AND THEIR PHYSICAL AND BIOLOGICAL DEGRADATION DURING WASTEWATER TREATMENT(2020) Motley, Taylor Ann; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids produced at wastewater treatment plants (WWTPs) are rich in recovered nutrients and are often recycled through soil amendment on agricultural land. Advanced solids treatment strategies, including thermal hydrolysis pretreatment (THP) and anaerobic digestion (AnD), are utilized to produce cleaner, safer biosolids based on EPA classifications. Despite the phase-out of the flame retardant polybrominated diphenyl ethers (PBDEs) from commercial use in the U.S., they are still present in biosolids and can be degraded to toxic byproducts during solids treatment. Their transformation during solids treatment is not well understood. This work shows that while phase-outs of PBDEs did not affect their concentrations in biosolids from the target WWTP, the implementation of THP-AnD treatment in 2014 led to increased PBDE degradation during solids treatment. This significantly lowered PBDE concentrations and shifted congener distribution to favor smaller, more toxic congeners in final biosolids compared to lime-stabilized biosolids historically produced at the target WWTP. Comparisons between the target WWTP and other AnD facilities without THP revealed that more efficient PBDE degradation occurred during THP-AnD treatment despite lower abundances of debrominating bacteria in digesters. Future work will examine if PBDE degradation during THP-AnD treatment is due to physical or biological processes.Item ENHANCED PRODUCTION OF BIOSOLIDS BY IMPROVED ACTIVATED SLUDGE CLARIFICATION AND STRUCTURED WATER ANALYSIS(2017) Liu, Xiaocen; Kjellerup, Birthe Veno; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids contain high contents of soil-required nutrients, so that have been widely applied in land application. The production of the biosolids depends on the clarification performance and dewaterability of the sludge, which are influenced by bioflocculation and structured water content, respectively. Therefore, research on sludge bioflocculation improvement and structured water content determination were proposed in this study. The result indicated that different activated sludge exhibited various bioflocculation limitations. Influence of the sludge characteristics such as the extracellular polymeric substances (EPS) composition, viscosity and floc size on the structured water content were also investigated. The results indicated that no significant correlation was observed between the EPS composition and the structured water content, however, the sludge floc size was positively correlated with it. The bioflocculation limitations were pinpointed, and how floc size influenced the structured water content needed further studies to improve sludge dewaterability, therefore, enhance the biosolids production quantitatively and qualitatively.Item FULL SCALE STUDY OF PATHOGEN, METAL POLLUTANTS, NUTRIENTS, AND POLYBROMINATED DIPHENYL ETHERS IN CLASS A BIOSOLIDS STABILIZED BY THERMAL HYDROLYSIS AND ANAEROBIC DIGESTION PROCESSES(2017) Wang, Xuanzhao; Torrents, Alba; Andrade, Natasha Almeida; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Class A biosolids are solid by-product of wastewater treatment which meet Environmental Protection Agency requirements to be used as fertilizer in farms, vegetable gardens, and can be sold directly to consumers. In 2014, this study’s target nutrient recovery facility adopted thermal hydrolysis pretreatment and anaerobic digestion to upgrade biosolids quality from Class B (previously lime-stabilized) to Class A. In order to certify if this newly produced material met all regulatory requirements, we performed laboratory analysis to characterize fecal coliforms, volatile solids, and metals content. In addition, we showed a baseline for nutrient management of total nitrogen, phosphorus, and the change in levels of polybrominated diphenyl ethers (PBDEs). Samples were collected for over a year since the start of THP-AD operation. Results were compared with the Class B biosolids produced at the same facility. Based on EPA standards, Class A biosolids were produced with stable quality after March, 2015, 16 weeks after process initiation. This work suggests that THP-AD is effective in producing Class A biosolids. In general, PBDEs in biosolids decreased from 1790 ± 528 (Class B) to 720 ± 110 µg/kg d.w. Our results suggest that the total levels of PBDEs decrease, however, the impact of the THP-AD on specific congeners are complex.Item ENVIRONMENTAL FATE OF POLYBROMINATED DIPHENYL ETHERS IN AGRICULTURAL SOILS WHICH HAVE RECEIVED BIOSOLIDS APPLICATION(2008) Andrade, Natasha Almeida; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Polybrominated diphenyl ethers (PBDEs) are used as additives in consumer products for their fire-retardant properties. While scientists observe PBDEs in various environmental media, little is known of their fate in soils. This study examines the potential fate of PBDEs in soils treated with biosolids. Surface soil samples were collected from commercial farms in the Mid-Atlantic region. Biosolids samples from the source wastewater treatment plant were collected to evaluate PBDE levels and trends. Results show that mean concentration of PBDEs in biosolids from this plant is 1496±158µg/kgd.w., mean concentration in soil from fields that had not received biosolids was 6.8µg/kgd.w., fields with a single application had a mean of 18µg/kgd.w., and fields with multiple applications had a mean of 52µg/kgd.w. Statistical analysis revealed that concentrations in the multiple application group were significantly higher than those in the single application group. This work suggests that PBDEs are relatively persistent in agricultural soils.Item GIS-Based Odor Dispersion Modeling for Measuring the Effect of DCWASA Biosolids in Reuse Fields(2006-05-04) Intarakosit, Eakalak; Baecher, Gregory B.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biosolids distributed to reuse fields for recycling and beneficial purposes can potentially create nuisance condition to surrounding community and possibly lead to odor complaints. Consequently, the public's lack of understanding of biosolids can limit the implementation of a worthwhile beneficial reuse program. This study developed a GIS-Based odor dispersion model as an alternative method for biosolids manager to measure the impact of biosolids odorants in the reuse fields by using the DCWASA biosolids fields as the case study. The results show the prediction maps expressed as concentration contours of predicted odorant area so-called sensation area or the area that concentration above the detection threshold (DT) or 1 . The results show that the sensation area usually occurs at low wind speed condition especially in early morning and night. The sensation area, moreover, is also sensitive to topographic features particularly elevated terrain.