Biosolids Compost Research Articles

Managing the value of composts as organic amendments and fertilizers in sandy soils

Nutrient rich composts are employed at low rates to minimize risks of N and P losses; this limits their value as soil improvers through C addition and the build up of soil organic matter. Blending with nutrient-poor composts such as those from the organic fraction of municipal solid waste could reduce the risks of nutrient losses while maintaining the positive effects on soil organic matter. We conducted a 2-yr experiment with composts of diverse origin: organic fraction of municipal solid waste (MC), cattle feedlot manure (FC), poultry litter (PC) and biosolids (BC), alone or blended (FC-MC, PC-MC) in a sandy soil under the humid warm climatic conditions of NE Argentina. We studied the effects of a single application (40 Mg ha−1) on the surface soil (0–10cm) properties of a permanent subtropical pasture through annual chemical and biological analyses. On five dates, available N and P were also determined at 0–10cm and 55–65cm. Soil total C and N increased over time while potential N mineralization and CO2 emission decreased. All amendments resulted in similar increments of soil C and N despite marked differences in quantity and quality of organic matter inputs. Because MC had substantial amounts of Ca carbonates, it contributed to a reduction of available P from manure composts through dilution and precipitation. The release of available P from biosolids composts (where P is bound to Fe and Al) was lower than from manure composts (where P is bound by Ca phosphates). The highest environmental risk from compost application would likely be the leaching of soluble N produced during the composting process and released immediately after field application. Blending with N-poor MC would contribute to nitrate dilution.

Influence of nutrients on oxidation of low level methane by mixed methanotrophic consortia.

Low-level methane emissions from coal mine ventilation air (CMV-CH4; i.e., 1 % CH4) can significantly contribute to global climate change, and therefore, treatment is important to reduce impacts. To investigate CMV-CH4 abatement potential, five different mixed methanotrohic consortia (MMCs) were established from soil/sediment sources, i.e., landfill top cover soil, bio-solid compost, vegetated humus soil, estuarine and marine sediments. Enrichment conditions for MMCs were as follows: nitrate mineral salt (NMS) medium, pH ~ 6.8; 25 °C; 20-25 % CH4; agitation 200 rpm; and culture period 20 days, in mini-bench-top bioreactors. The enriched cultures were supplemented with extra carbon (methanol 0.5-1.5 %, formate 5-15 mM, and acetate 5-15 mM), nitrogen (nitrate 0.5-1.5 g L(-1), ammonium 0.1-0.5 g L(-1), or urea: 0.1-0.5 g L(-1)), and trace elements (copper 1-5 μM, iron 1-5 μM, and zinc 1-5 μM) in different batch experiments to improve low-level CH4 abatement. Average CH4 oxidation capacities (MOCs) of MMCs varied between 1.712 ± 0.032 and 1.963 ± 0.057 mg g(-1)DWbiomass h(-1). Addition of formate improved the MOCs of MMCs, but the dose-response varied for different MMCs. Acetate, nitrate and copper had no significant effect on MOCs, while addition of methanol, ammonium, urea, iron and zinc impacted negatively. Overall, MMCs enriched from marine sediments and landfill top cover soil showed high MOCs which were largely resilient to nutrient supplementation, suggesting a strong potential for biofilter development for industrial low-level CH4 abatement, such as those present in CMV.

The effect of green manure and organic amendments on potato yield, nitrogen uptake and soil mineral nitrogen

Fertility management is challenging for organic crops with intensive nutrient demands such as potatoes (Solanum tuberosum L.). Four crop sequences varying in pre-potato green manures as main plots and four fertility treatments applied in the potato phase only [control, inorganic fertilizer (FERT), municipal solid food waste compost (MSW) and paper mill biosolid compost (PMB)] as subplots were compared in five-year organic potato rotations in Eastern Canada. Potato yields did not differ significantly between crop rotations; however, soil amendments had significant impacts on potato yields. Averaged across years, total tuber yields were in the order; FERT (34.2 Mg ha−1) > MSW (29.6 Mg ha−1) > control (26.5 Mg ha−1). Total potato N uptake (TNU) levels were 89, 115, 107 and 147 kg N ha−1, respectively, for control, MSW, PMB and FERT, and were greater when potato followed red clover (119–124 kg N ha−1) compared with oat/pea/vetch mixture (107–108 kg N ha−1). Plant N use efficiency (NUE) was 299, 263, 263 and 235, respectively, for control, MSW, PMB and FERT. Pre-plant soil mineral N (SMN) ranged between 39 and 112 kg N ha−1 among different crop rotations. During the tuber initiation stage, SMN ranged between 40 and 66 kg N ha−1 while during tuber bulking it ranged between 10 and 14 kg N ha−1 among different crop rotations and soil amendments. Post-harvest SMN ranged between 8 and 30 kg N ha−1 for all rotations and amendment treatments.

Carbon Sequestration in Restored Soils by Applying Organic Amendments

AbstractThe study of different natural carbon sinks has become especially important because of climate change effects. The restoration of contaminated areas can be an ideal strategy for carbon sequestration. The studied area was affected by toxic Aznalcóllar mine spill in 1998. Restoration process of the contaminated area was based, mainly, on the use of two organic amendments: leonardite (LE) and biosolid compost (BC). The objective of this study was to verify whether the application of these amendments promotes the long‐term carbon sequestration in this soil. Five treatments were established: untreated control, biosolid compost (doses 4 and 2) and leonardite (doses 4 and 2). The addition of amendments implied an improvement in soil quality that was directly related to the amendment dose: decrease in bulk density, increase in pH, higher respiration rates and an improvement in the stratification ratio. Dose‐dependent changes in the molecular composition of soil organic matter were shown by nuclear magnetic resonance analysis. Both amendments promoted carbon retention, although because of the low mineralization rates of soil organic matter in LE treatments, the carbon storage was higher. The dosage effect on the carbon balance was more important in LE treatments, whereas in the BC treatments, the balance was similar for both doses. Our findings suggest that LE4 significantly increased the total organic carbon and it was the most suitable treatment for long‐term carbon storage, because of its molecular composition rich in relatively stable aromatic and lignin‐derived compounds. Copyright © 2015 John Wiley & Sons, Ltd.

Three-year study of fast-growing trees in degraded soils amended with composts: Effects on soil fertility and productivity

Currently, worries about the effects of intensive plantations on long-term nutrient supply and a loss of productivity have risen. In this study two composts were added to degraded soils where this type of intensive crops were growing, to avoid the soil fertility decrease and try to increase biomass production. For the experiment, two degraded soils in terms of low organic carbon content and low pH were selected in South-West Spain: La Rábida (RA) and Villablanca (VI) sites. Both study sites were divided into 24 plots. In RA, half of the plots were planted with Populus x canadensis “I-214”; the other half was planted with Eucalyptus globulus. At the VI site, half of the plots were planted with Paulownia fortunei, and the other plots were planted with Eucalyptus globulus. For each tree and site, three treatments were established (two organic composts and a control without compost), with four replications per treatment. The organic amendments were “alperujo” compost, AC, a solid by-product from the extraction of olive oil, and BC, biosolid compost. During the three years of experimentation, samples of soils and plants were analyzed for studying chemical and biochemical properties of soil, plant growth and plant nutritional status and biomass production. The composts increased total organic carbon, water-soluble carbon, nutrients and pH of soil only in the most acidic soil. Soil biochemical quality was calculated with the geometric mean of the enzymatic activities (Dehydrogenase, β-glucosidase, Phosphatase and Urease activities) determined in soils. The results showed a beneficial improvement in comparison with soils without compost. However, the best results were found in the growth and biomass production of the studied trees, especially in Eucalyptus. Nutritional levels of leaves of the trees were, in general, in the normal established range for each species, although no clear effect of the composts was observed. The results of this study justify the addition of compost to guarantee good biomass production and maintain or improve soil management in degraded soils, especially in acid soils.

Organic amendments for risk mitigation of organochlorine pesticide residues in old orchard soils

Performance of compost and biochar amendments for in situ risk mitigation of aged DDT, DDE and dieldrin residues in an old orchard soil was examined. The change in bioavailability of pesticide residues to Lumbricus terrestris L. relative to the unamended control soil was assessed using 4-L soil microcosms with and without plant cover in a 48-day experiment. The use of aged dairy manure compost and biosolids compost was found to be effective, especially in the planted treatments, at lowering the bioavailability factor (BAF) by 18–39%; however, BAF results for DDT in the unplanted soil treatments were unaffected or increased. The pine chip biochar utilized in this experiment was ineffective at lower the BAF of pesticides in the soil. The US EPA Soil Screening Level approach was used with our measured values. Addition of 10% of the aged dairy manure compost reduced the average hazard quotient values to below 1.0 for DDT + DDE and dieldrin. Results indicate this sustainable approach is appropriate to minimize risks to wildlife in areas of marginal organochlorine pesticide contamination. Application of this remediation approach has potential for use internationally in areas where historical pesticide contamination of soils remains a threat to wildlife populations.

Getting to the root of urban tree health

Getting to the root of urban tree health

Assessment of trace element phytoavailability in compost amended soils using different methodologies

This study evaluates the effects of two soil amendments and the growth of two plant species on labile trace element (TE) fractions in two different contaminated soils. We studied the effects of two organic amendments (biosolid compost and alperujo compost) and two plant species (Medicago polymorpha and Poa annua) on pH, total organic carbon (TOC), and TE availability, by three extraction methods (CaCl2 aqueous solution, soil pore water (SPW), and diffusive gradient in thin film (DGT)), in two contaminated soils with contrasting pH values (Aznalcazar, 6.53, and Vicario, 3.48) in a 118-day pot experiment. The effects of the composts on labile TE fractions were compared with element concentrations in plants. No relevant effects of amendments and plants were found on the physical and chemical characteristics of the Aznalcazar soil. However, the addition of amendments was essential for plant species growing in the acid Vicario soil. In this soil, amendments and plant growth increased pH and TOC and reduced substantially TE bioavailability. Although absolute values of bioavailable TE contents obtained by the three methods were very different and followed the trend CaCl2 extraction > SPW > DGT, these values follow a similar behavior in the two studied soils and for the two species. The results demonstrate that the application of organic amendments are suitable for remediating acid TE-contaminated soils, for the establishment of a vegetation cover on previously bare soils for reducing wind and water erosion and for reducing labile TE fractions to prevent leaching of pollutants into subsoil or groundwater layers. Moreover, the results obtained in this study pointed out that under microcosm conditions, the three methods tested (CaCl2 extraction, SPW, and DGT) to predict TE bioavailability were highly correlated.

Evaluation of phytostabilizer ability of three ruderal plants in mining soils restored by application of organic amendments

Abstract Abandoned mines involve a serious environmental problem because these soils contain high levels of trace elements. The aim of the study was selecting the most adequate autochthonous plant species to stabilize contamination and improve soil quality of a contaminated soil from an abandoned mine. For this purpose three plant species were studied: Poa annua , Medicago polymorpha and Malva sylvestris , in combination with two organic amendments (biosolid compost (BC) and “alperujo” compost (AC)) and a soil without amendments (CO). Soil pH increased due to the effect of amendments under all studied plants, which promotes the immobilization of trace elements in soil. Water soluble C (WSC) increased with the addition of both amendments and the highest concentration was found in soils under M. polymorpha . The evolution of trace element availability in soil depended on the amendment, plant species and characteristics of the element. The best treatment to stimulate biomass production was AC. The highest concentration of As and Pb was found in P. annua whereas the highest concentration of Mn and Zn was found in M. sylvestris . Considering chemical and biochemical properties, and concentrations in shoots M. polymorpha would be the most suitable plant to stabilize trace elements and improve soil quality. Nevertheless, the best results were obtained with the plant-amendment combination.

Use of alum water treatment sludge to stabilize C and immobilize P and metals in composts.

Alum water treatment sludge is composed of amorphous hydroxyl-Al, which has variable charge surfaces with a large Brunauer-Emmett-Teller (BET) surface area (103 m(-2) g(-1)) capable of specific adsorption of organic matter molecules, phosphate, and heavy metals. The effects of adding dried, ground, alum water treatment sludge (10% w/w) to the feedstock for composting municipal green waste alone, green waste plus poultry manure, or green waste plus biosolids were determined. Addition of water treatment sludge reduced water soluble C, microbial biomass C, CO2 evolution, extractable P, and extractable heavy metals during composting. The decrease in CO2 evolution (i.e., C sequestration) was greatest for poultry manure and least for biosolid composts. The effects of addition of water treatment sludge to mature green waste-based poultry manure and biosolid composts were also determined in a 24-week incubation experiment. The composts were either incubated alone or after addition to a soil. Extractable P and heavy metal concentrations were decreased by additions of water treatment sludge in all treatments, and CO2 evolution was also reduced from the poultry manure compost over the first 16-18 weeks. However, for biosolid compost, addition of water treatment sludge increased microbial biomass C and CO2 evolution rate over the entire 24-week incubation period. This was attributed to the greatly reduced extractable heavy metal concentrations (As, Cr, Cu, Pb, and Zn) present following addition of water treatment sludge, and thus increased microbial activity. It was concluded that addition of water treatment sludge reduces concentrations of extractable P and heavy metals in composts and that its effect on organic matter stabilization is much greater during the composting process than for mature compost because levels of easily decomposable organic matter are initially much higher in the feedstock than those in matured composts.

Assisted Natural Remediation of a Trace Element-Contaminated Acid Soil: An Eight-Year Field Study

There are many remediation techniques for organic contaminated soils, but relatively few of them are applicable to trace element-contaminated soils. A field experiment was carried out to investigate assisted natural remediation (ANR) of an acid soil contaminated by As, Cd, Cu, Zn and Pb using one inorganic amendment, sugar beet lime (SL), and two organic amendments, biosolid compost (BC) and leonardeite (LE). The experiment was arranged in a completely randomized block design with four treatments in three replicates: 1) a non-amended control (NA); 2) SL amended at 30 Mg ha−1 year−1; 3) BC amended at 30 Mg ha−1 year−1 and 4) LE amended at 20 Mg ha−1 year−1 plus SL amended at 10 Mg ha−1 year−1 (LESL). The amended plots received two doses of each amendment (DO2): one in October 2002 and another in October 2003. The plots were then divided in half into two subpolts and one subplot received another two doses of the same amendments (DO4) in October 2005 and October 2006. In 2011, the pH values of the amended soils were greater than that of the NA soil, with the SL-amended soil showing the highest pH. Total organic carbon (TOC) was also greater in the amended soil, and greater with DO4 than with DO2. Amendments reduced the concentrations of 0.01 mol L−1 CaCl2-extractable Cd, Cu and Zn, especially in the SL-amended soil. Plant cover of colonizing vegetation was enhanced by amendments, but was independent of amendment doses. Changes in soil properties from 2003 to 2011 showed that the first amendment application of DO2 caused a high differentiation between all the amendment treatments and the NA treatment. After the second application of DO2, soil pH and TOC continued increasing slowly. Further two applications of amendments (DO4) caused differences only in the organic treatments. Plant cover increased over time in all the treatments including NA. It could be concluded that the slow and steady natural remediation of this soil could be enhanced by amendment application (ANR).

Antibiotic Degradation During Thermophilic Composting

Residual antibiotics in land-applied manure and biosolids present a potential threat to public and ecological health. It remains important to determine antibiotic degradation efficiencies for manure and biosolids waste management practices and to identify conditions that enhance antibiotic degradation. The fates of the antibiotics florfenicol, sulfadimethoxine, sulfamethazine, and tylosin were studied during pilot-scale static pile thermophilic composting, and the effects of temperature and feedstock particles on antibiotic degradation rates were tested. The antibiotics were spiked into dairy manure solids and wastewater biosolids, and treatments included aerated and non-aerated manure and biosolids/wood-product (1:3 v/v) composting. Results showed no significant differences between aerated and non-aerated treatments; on average, ≥85, ≥93, and ≥95 % antibiotic degradation was observed after 7, 14, and 21 days of composting. Greater antibiotic degradation was observed in manure compost compared to biosolids compost for florfenicol (7, 14, 21, 28 days) and tylosin (14, 28 days); however, there was no significant difference for sulfadimethoxine and sulfamethazine. Peak temperatures were 66–73, and ≥55 °C was maintained for 6–7 days in the biosolids compost and 17–20 days in the manure compost. Bench-scale experiments conducted at 25, 55, and 60 °C showed that lower temperature decreased degradation of the sulfonamides and tylosin in both feedstocks and florfenicol in the biosolids. The presence of compost particles increased antibiotic degradation, with time to 50 % degradation ≤2 days in the presence of solids (60 °C) compared to no degradation in their absence. These results indicate that thermophilic composting effectively degrades parent antibiotic compounds in manure and biosolids.

Comparison of composted biosolid substrate for containerized turfgrass production

Composts produced from composting municipal sewage sludge with bulking agent, namely hazelnut husk (HH), pine litter (PL), corn straw (CS) and sawdust (SW), were seeded with turfgrass mix and cultivated in a container to compare the suitability of composted substrates to produce turfgrass in greenhouse conditions. The performance of substrate was determined by both substrate properties compared to standard peat and by measuring plant growth parameters on each substrate during turfgrass sod establishment. In general, the physico-chemical properties of all substrates were satisfactory for container substrates, but HH and PL substrates performed better in plant growth parameters than in SW and CS composts. The comprehensive growth index values obtained for plants growing in peat, HH and PL were 0.94, 0.87 and 0.84, respectively, which were higher than those in the CS and SW. Plant growth showed linear above-ground dry matter accumulation in all substrates, but was slower in SW and CS. HH and PL substrates appeared to be suitable for containerized sod production for natural soil and peat substitution. Biosolid proved to be an efficient component as a nutrient source ingredient of composted substrates for turfgrass.

Soil residuals and plant uptake of Cu and Zn from biosolids applied to a clay loam soil under field conditions in Victoria, Australia

A field experiment was conducted to investigate the effects of incorporating anaerobically digested dewatered biosolids (DWB) and composted biosolids (CB) on the availability of the heavy metals Cu and Zn to canola (Brassica napus cv. Beacon) and oats (Avena sativa cv. Echidna) grown in a clay loam soil. DWB at rates of 0, 5, 25, 45 and 65 t dry solids (ds) ha–1 and CB at rates of 0, 10 30, 50 and 70 t ds ha–1 were incorporated into the soil to a depth of approximately 15 cm. The plots were arranged in triplicate, in a randomised complete block design. Canola and oat seeds were sown at a seeding rate of 5 and 100 kg ha–1, respectively. After the crop harvest, total and diethylenetriamine penta-acetic acid (DTPA)-extractable heavy metals in biosolids-amended soil were determined using X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Total metals in plant leaves were analysed using ICP-MS. In these biosolids, only Cu and Zn were high enough to significantly increase their concentration in the soil and plant tissue. The results showed that application of biosolids significantly (P < 0.001) increased DTPA-extractable and total concentrations of Cu and Zn in the amended soil. The ratio of DTPA-extractable to total (XRF) Cu and Zn also changed with increasing application rates of DWB and CB. The change in the ratio was more pronounced in soils receiving DWB, probably associated with the significant (P < 0.001) decrease in soil pHw with their loading rate. Positive correlations were also noted between the application rate of biosolids and the Cu and Zn levels in the canola and oat leaves.

Seasonal Dynamics of N, P, and K in an Organic and Inorganic Fertilized Willow Biomass System

The seasonal variations in soil nutrient supply and bioavailability were assessed in a willow biomass crop (Salix miyabeana, SX64) treated with 150 and 200 kg available N ha−1of commercial fertilizer (CF), biosolid compost (BC), dairy manure (DM), and control (CT0) at Delhi, NY. Plant root simulator probes were used to measure nutrient supply (inside) and bioavailability (outside) of root exclusion cylinders. Measurements were made in September 2008 and May, August, and October of 2009. Soil moisture content (θd)and foliar nutrient concentrations were also determined. The BC treatments increased soil P supply more than CF and CT0. The supply ofNH4+and K in the soil increased in August but their bioavailability increased in May and October. SoilNO3-and P supply and bioavailability were both high in May. Foliar N and K concentrations were significantly high in May and low in August which could be due to dilution effect caused by increased soil moisture foliar dry weight. Foliar P concentrations increased in September and October. The observed higher soilNO3-mineralization and plant uptake in May suggest that in high soilNO3-conditions willow biomass crops can level and minimize leaching out of the root zone into groundwater.

Effect of Composts Combined with Chemical N Fertilizer on Nitrogen Uptake by Italian Ryegrass and N Transformation in Soil

Combining compost with sufficient chemical N fertilizer (CF) in agricultural lands is a popular practice to reduce the amount of inorganic nitrogen and accumulation of non-nutrient constituents in soils. A pot culture experiment was conducted to study the effects of 130 mg N of either solids waste compost (Scomp) or biosolids waste compost (Bcomp) complemented with 130 mg (CF, 1N) and 260 mg·N·pot-1 (CF, 2N) as 15N labeled (NH4)2SO4 (13.172 atom %) on growth and N uptake by Italian ryegrass. A separate soil incubation without plants was set up by only blends of Scomp and CF. The results from pot culture experiment show that total plant biomass and N uptake from Bcomp were significantly higher than Scomp alone. Scomp combined with CF improved yield and N uptake over those of Scomp alone. For Scomp + 1N treatment, plant nitrogen uptake derived from compost and CF accounted for 29% and 56% of added N from Scomp and CF, respectively. The incubation study indicates that 16.08 - 29.62 mg·N·kg-1·soil·day-1 from inorganic-N were immobilized into organic pools, while only 0.40 - 0.66 mg·N·kg-1·soil·day-1 from organic-N were mineralized to inorganic pools. Because a part of additional N could be tied up in organic form, combining solids compost with chemical N fertilizer therefore need to consider the effective use of compost-N.

Striking Black Gold: Challenges and Triumphs of Designing, Constructing, Permitting, and Marketing a Biosolids Compost Program

Striking Black Gold: Challenges and Triumphs of Designing, Constructing, Permitting, and Marketing a Biosolids Compost Program

Persistent effect of organic matter pulse on a sandy soil of semiarid Patagonia

Studies of degraded semiarid regions have shown that organic residue addition is a sound restoration alternative. We examined the effects of a single dose (40 Mg ha−1) of biosolids compost (BC) and compost of the organic fraction of municipal solid waste (MC) 6 years after they were applied to a sandy soil of NW Patagonia. Results were compared with those of inorganic fertilization (IF, 100 kg N + 35 kg P ha−1) treatment and of unamended control. We measured plant cover, biomass, and diversity and chemical, biological, and biochemical soil properties. We did not find any significant effect of treatments on plant attributes. However, effects on soil properties were significant and more persistent with composts than with IF, especially with BC, which had higher organic C and nutrients than MC. Total soil C and N were twice as high in the BC-amended soil as in the control and IF soils. Soil extractable P was 4-fold and 2-fold higher in BC- and MC-treated soils, respectively, than in the control soil, and even higher than in the IF treatment in response to BC. The highest β-glucosidase and acid phosphomonoesterase activities were found in the BC-treated soil, related to higher C and P in the soil and to higher activities of both enzymes in the biosolids compost. The highest phenol oxidase activity was found in MC and in the MC-treated soil. Potential respiration and K2SO4-extractable C were higher in the compost-treated soil, but there was no difference in microbial biomass C between the compost-treated and the control soils. Despite the fact that the soil was coarse textured and a single moderate dose of compost was applied, recovery of soil chemical, microbiological, and biochemical properties was long-lasting, indicating that application of urban compost is a feasible restoration practice in this semiarid region.

Biosolids Composting Technology: Where it Has come from and where it is Going

Biosolids Composting Technology: Where it Has come from and where it is Going

Ciprofloxacin Residues in Municipal Biosolid Compost Do Not Selectively Enrich Populations of Resistant Bacteria

Biosolids and livestock manure are valuable high-carbon soil amendments, but they commonly contain antibiotic residues that might persist after land application. While composting reduces the concentration of extractable antibiotics in these materials, if the starting concentration is sufficiently high then remaining residues could impact microbial communities in the compost and soil to which these materials are applied. To examine this issue, ciprofloxacin was added to biosolid compost feedstock to achieve a total concentration of 19 ppm, approximately 5-fold higher than that normally detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) (1 to 3.5 ppm). This feedstock was placed into mesh bags that were buried in aerated compost bays. Once a week, a set of bags was removed and analyzed (treated and untreated, three replicates of each; 4 weeks). Addition of ciprofloxacin had no effect on the recovery of resistant bacteria at any time point (P = 0.86), and a separate bioassay showed that aqueous extractions from materials with an estimated 59 ppm ciprofloxacin had no effect on the growth of a susceptible strain of Escherichia coli (P = 0.28). Regression analysis showed that growth of the susceptible strain of E. coli can be reduced given a sufficiently high concentration of ciprofloxacin (P < 0.007), a result that is consistent with adsorption being the primary mechanism of sequestration. While analytical methods detected biologically significant concentrations of ciprofloxacin in the materials tested here, the culture-based methods were consistent with the materials having sufficient adsorptive capacity to prevent typical concentrations of ciprofloxacin residues from selectively enriching populations of resistant bacteria.