Tracking the Movement of Biosolid Leachates Through Soils...
Throughout the state, we are applying biosolids (municipal wastewater treatment sludge) to the land. The movement of the organic compounds, metals, and nutrients from these amendments is mediated by their solubility, the properties of the soils where they are applied, and the precipitation (rainfall and irrigation). In some situations, the application of biosolids can have a significant impact on groundwater quality. In this session, speakers will describe some of the ways the amendments are applied in Maine, give examples of tools and techniques used to monitor the movement of the leachates in soils, and discuss their potential impacts on Maine's groundwater quality.

Session Chair:
Laurie Osher, University of Maine
Laurie is Assistant Professor of Soil and Water Quality at the University of Maine (Orono). Her research includes the study of ecosystem nutrient cycling, the movement of nutrients and contaminants from surface to groundwater, the impact of land use change on soil resources, and quantification of C stored in a range of soil ecosystems. She was educated at Cornell University (BS), North Carolina State University (MS), and the University of California at Berkeley (PhD). Dr. Osher worked with EPA's Natural Health and Environmental Effects Research Laboratory in Athens, GA prior to joining the faculty at the University of Maine.
 

Richard S. Behr, Maine Department of Environmental Protection
17 State House Station, Augusta, ME 04333

Can Residuals be Land Applied or Stockpiled without Causing Groundwater Impacts?
Every year Maine produces millions of gallons and several thousand tons of residuals, including: municipal sewage sludge, primary and secondary papermill sludge, woodash, wood wastes, lime mud and kiln dust. Many of these residuals represent a valuable resource as they contain agricultural nutrients, beneficial organic matter and other important elements and minerals. Maine has developed regulations to manage the stockpiling and agronomic use of the various residuals. Although these regulations are intended to protect groundwater quality, few projects currently have properly designed and implemented monitoring programs. This presentation includes groundwater quality data from five residual operations. Two sites used residuals to create a manufactured topsoil to augment existing soil. There are two ongoing land application projects: the first is a large tract of agricultural land used to apply secondary municipal sewage sludge; and the second is a municipally operated septage spreading operation. The final site was used to stockpile municipal sewage sludge before application.

The groundwater quality data reveals some level of groundwater impact at each site. Nitrate concentrations exceeded the drinking water standard at one or more wells at each site. A variety of elements leached directly from the residual were elevated in groundwater at each site. At three sites the leaching and subsequent biodegradation of organic carbon significantly decreased dissolved oxygen concentrations. And, the development of anaerobic conditions at one site has released iron, manganese and arsenic from the aquifer material.

Review of the data indicates some level of impact at all five sites. However, the extent and magnitude of the impacts are likely ephemeral when there is a single residual application. Groundwater quality impacts may be minimized at sites underlain by highly transmissive materials. This suggests altering current management practices could improve groundwater quality.
 

David Firmage, Jonathan Brooks, and Christian Mastrodonato
Colby College, 5730 Mayflower Hill, Waterville, ME 04901, 207/872-3319, dhfirmag@colby.edu

An Analysis of Material and Leachate From Composted Sewage Sludge and Ditching Soil
The Maine Department of Transportation (MDOT) has proposed using a 2:1 mixture of ditching material and composted sludge to stabilize roadside embankments. In order to determine if harmful levels of toxic substances could leach from the proposed material, plexiglass structures were built to simulate roadside embankments and leachate was evaluated from different soil mixes. Mixes included compost, ditching material and a 2:1 mix of ditching material and compost left fallow and planted with a clover and grass mixture. Each section of the simulated embankment was on a 1:2 slope, measuring 1.15 X 1.21 X 0.12 meters, and held soil at a depth of 12 cm. Rain events of varying intensities were simulated and ICP analysis was performed on the leachate to determine concentrations of potentially harmful substances. In addition, the compost, ditching material and grass were digested and analyzed. The concentrations of metals in the compost material were all below maximum levels allowed by the EPA for land application of soil amendments. The metals found in the compost material leached more readily than those in the ditching material. The leachate from the compost material initially showed several metal concentrations above EPA drinking water standards. These metals included arsenic, lead and chromium. The leachate from ditching material did not show significant levels of toxic heavy metals, but had elevated concentrations of sodium and iron. Most toxic metals were not detectable in leachate collected from the compost-ditching soil mixture. Lead was the only metal which leached from the mixture in concentrations at or above EPA drinking water standards. The results from the ICP analysis of the 2:1 mixture of ditching material and compost proposed for use by the Department of Transportation did not indicate concentrations of potentially harmful substances that could negatively impact ground water in the short term. The material does have potentially harmful levels of lead and phosphorus that could have long-term, detrimental effects in sensitive areas.
 

Mark A. King, Residuals Utilization Program, Maine Department of Environmental Protection
17 State House Station, Augusta, ME 04333, mark.a.king@maine.gov

Agronomic Utilization of Sludge in Maine, 'Trends in Sludge Management'
Maine has regulated the agronomic utilization of municipal sewage sludge since the late 1970's. The Industry trend in residual utilization has focused on diversion of sludge away from traditional practices such as landfilling and land application towards more complex technologies, including composting and alkaline-thermal stabilization. Possible contributing factors for this continuing trend include: decreasing landfill space, stricter regulations and organized public opposition to sludge landspreading practices, and finally, increasing public acceptance of "Class A" products.
 

Laurie Osher, Soil & Environmental Sciences, University of Maine
214A Deering Hall, Orono, ME 04469, 207/581-2957, laurie@maine.edu

Using Biosolids as Landscape Amendments: Potential Impacts to Groundwater
Composted municipal wastewater treatment sludge (biosolids) makes an excellent landscape amendment, especially for sites where lack of topsoil or shallow soils limit the site's ability to be vegetated or revegetated after disturbance. Most biosolids contain no coarse fragments, have high organic matter contents, are high in nitrogen, but may also contain a range of heavy metals. When applied in place of soil in constructed landscapes, biosolids are commonly irrigated. This raises the concern about leaching of N and metals into the groundwater or to adjacent lakes and streams.

We compared leachate from soil columns amended with biosolids, topsoil, and a 1:1 biosolid sand mix to leachate collected from unamended soil columns. To simulate landscaped conditions, columns were irrigated with groundwater from the site at a rate of one inch per week. The concentrations of ammonium nitrate and metals in the leachates from the columns were collected and analyzed monthly. Biosolid-amended columns had higher concentrations of NH4+ and NO3- in leachate than topsoil amended and unamended columns. Where biosolids were mixed with sand, nitrate in the leachate exceeded ammonium, indicating a well-aerated environment. Leachates from columns amended with the biosolid/sand mix also had higher metal concentrations than those amended with biosolids only. When these biosolids are added to soil surfaces in thicknesses of 30 cm or less, metal concentrations in leachates will be below current EPA drinking water standards. However, when a biosolid/sand mixture is applied in thicknesses of 30 cm or greater, concentrations of Ba and Cd in leachates will be above the current EPA drinking water standards. The development of Best Management Practices identifying maximum application depth of these materials is advised.
 

John M. Peckenham, Mitchell Center1, James Nadeau, University of Maine2, Aria Amirbahman, University of Maine2
1. 5710 Norman Smith Hall, University of Maine, Orono, ME 04469, 207/581-3254, jpeck@maine.edu
2. Dept. of Civil and Environmental Engineering, Boardman Hall, Orono, Maine 04469

Nitrogen Loss From The Controlled Field Stacking of Biosolids
Field stacking of biosolids prior to utilization is a common practice in Maine. The Maine Department of Environmental Protection (MDEP) has been concerned that nitrate-N leached from stockpiled biosolids may have adverse effects on groundwater quality. Current Maine regulations have strict siting standards for field stacking (since October 2002). This rule affects most of the 50 Publicly-Owned Treatment Works (POTW) that currently apply biosolids to land. The field experiment in our study was designed to measure the quantity and composition of leachate derived from biosolids due to de-watering and precipitation. Mass loading of nitrogen species (nitrate, nitrite, ammonium, and total nitrogen) leaving the stockpiles was determined by placing biosolids on a plastic sheet (area ~111 square meters) to collect liquid flowing through and over the pile. Biosolid stockpile geometry affects the type and amount of leachate generated. Leachate chemistry was dominated by total nitrate and ammonia in concentrations >1,000 mg/L and nitrate concentrations were found to be less than 1 mg/L. Cumulative mass loading under ambient field conditions was approximately 10% of the total nitrogen in the stockpile over a period of three months.
 

James Nadeau, University of Maine1, John M. Peckenham, Mitchell Center2, Aria Amirbahman, University of Maine1
1. Dept. of Civil & Environmental Engineering, Boardman Hall, Orono, ME 04469, 207/581-2185, james.a.nadeau@umit.maine.edu
2. 5710 Norman Smith Hall, University of Maine, Orono, ME 04469

Trace Metal Movement from Field Stacked Biosolids
We have recently completed a study to determine nitrogen speciation in and loss from the field stacked biosolids. Trace metal analysis on the leachate through the biosolids stockpile and in the shallow ground water affected by the stockpile were conducted in an effort to determine if further study of trace metal mobilization was warranted. The preliminary data show significant metal transport from the experimental lined bed. Samples collected from pan lysimeters from 1' to 3' below the surface also show significant metal mobility through the soil column. We propose that metal transport is enhanced via speciation with respect to the dissolved organic matter, and ion exchange due to high NH4+ concentrations.