LEACHABILITY AND SORPTIVITY OF INCINERATED BIOSOLID ASH

1 online resource (166 pages) : PDF

2017

University of North Carolina at Charlotte

The byproduct of incinerated biosolids (biosolid ash) was evaluated for land application through laboratory and field testing of leachability and sorption capacity. Field testing involved vacuum lysimeters that were installed to monitor the leachate composition. All constituents detected by these lysimeters were below regulatory limits with the exception of one sample with manganese and silver above the limit. Laboratory column leaching tests were performed using the biosolid ash. Six elements, manganese, nickel, selenium, arsenic, lead, and silver, leached out of the columns at concentrations above the regulatory limits. All but arsenic returned to safe limits after the first 0.2 L/S ratio. Arsenic remained above the limit from 0 – 4.5 L/S ratio. Leachability results derived from the laboratory were different from field measurements during the first 2 L/S ratios collected. There were several field conditions which were not replicated in the laboratory and may explain the variance. In the field, biosolid ash was land applied six months prior to the installation of instrumentation and data collection. Based on precipitation records, estimated thickness, porosity, and using 100% infiltration (evapotranspiration rates not known for time period) approximately 1.8 pore volumes of infiltration passed through the biosolid ash prior to lysimeter installation resulting in no data for the first flush of the system. This would have been equivalent to a first flush where the pore fluids may contain higher constituent concentrations. Compacted dry biosolid ash density in the field was estimated at 7.775 kN/m3 (49.5 pcf) while in the laboratory it was 9.897 kN/m3 (63 pcf). This difference affects leachability results through concomitant changes in the seepage velocity and contaminant retardation. Similarly, column experiments were conducted under saturated conditions while in the field this degree of saturation varied from approximately 13% to 61%. The leachate composition from field and laboratory leaching tests was compared with groundwater regulations to determine contaminants of concern. These contaminants (arsenic, manganese, phosphorus, and selenium) were then synthetically prepared by mixing with deionized (DI) water and used in laboratory column studies to evaluate the sorption capacity of site soils. The estimated Kd for selenium is between 2 and 4 mL/g. No Kd could be determined for the other constituents although their absence in the effluent suggests a value greater than this range. Several physical characteristics were determined including particle size analysis, moisture content, proctor test, loss of ignition, permeability, and specific gravity. The values were similar to the literature. A comparison between coal fly ash, municipal solid waste ash (MSW), and biosolid ash was conducted. The physical characteristics were all similar except particle size. Coal fly ash had significantly smaller particles passing a No. 200 sieve. The primary differences between the three ash categories was the elemental composition. Both coal fly ash and MSW ash had significantly higher concentrations of numerous constituents while biosolid ash was significantly higher only in phosphorus according to literature as well as these results.

masters theses

Civil engineering
Environmental geology

M.S.

Biosolid Ash
EPA Method 1314
Incineration
Leachability
Phosphorus
Vacuum Lysimeter

Civil Engineering

Daniels, John

Langley, William
Ogunro, Vincent
Rubin, Albert

Thesis (M.S.)--University of North Carolina at Charlotte, 2017.

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Boivin_uncc_0694N_11316

http://hdl.handle.net/20.500.13093/etd:364