Disinfection By-Product Formation during Long-Term Water Storage in Alaska

In many areas of Northern and Western Alaska, small streams and shallow lakes serve as community raw water supplies. These water supplies freeze completely during winter. In order to supply drinking water during the 6–9 month winter, communities store water that was treated during summer. A chlorine residual is maintained in the stored water. Raw water sources derived from surface water may be heavily laden with dissolved organic matter. At utilities where organic matter escapes treatment, the potential for accumulation of disinfection by-products (DBPs) during storage is a significant health concern. The following study was performed to evaluate this potential threat. Water was collected from five operating utilities, four that normally store water for 6–9 months and one that produces drinking water year-round. Raw, filtered (i.e., unchlorinated) and “finished” (i.e., filtered and chlorinated) water samples were collected during the summer pumping season and stored in the laboratory for 8 months. In order to mimic practice in the field, the chlorine residual was maintained in the finished water for the full storage period. While the concentration of DBPs in the finished water varied over the study period, there was not a statistically significant trend from the third to the eighth month of storage. The observed DBP values were strongly a function of the type of treatment system used. Those systems passing more organic matter had higher DBP values throughout the storage period. The ultraviolet absorbance at 254 nanometers ?start(UV254)end? decreased continuously in the finished water coincident with chlorine consumption. ?startUV254end?, often used as a surrogate for DBPs, remained constant during the entire storage periodin raw and filtered water samples. Filtered water that was stored prior to chlorination accumulated fewer DBPs than finished water that was continuously chlorinated during the storage period. This result suggests that storing filtered water instead of finished water for long periods would limit DBP exposure to consumers. This conclusion was based on a comparison of DBP formation potentials (i.e., raw and filtered water) to DBPs (i.e., finished water). It is important to note that DBP formation potentials are based on a ?start24?hend?chlorine contact time. If long term storage were provided for filtered water, a smaller volume of secondary storage would still be needed to provide contact time for disinfection.     

Iron Oxide Enhanced Chlorine Decay and Disinfection By-Product Formation

This study investigates the interaction of natural organic matter with iron oxide (goethite) on chlorine decay, disinfection by-product (DBP) formation, and DBP compound speciation [total trihalomethanes (TTHM4) and haloacetic acids (HAA5)]. Batch experiments were conducted with goethite, multiple finished drinking waters, variable chlorine dose, and fixed pH 8. The overall objective was to assess natural organic matter (NOM) adsorption onto goethite and its effect on chlorine decay and DBP formation. Chlorine consumption always increased in the presence of goethite and is attributed to an increase in the reactivity and/or modification of adsorbed NOM. Adsorbed NOM also led to an overall increase in TTHM4, however, HAA5 formation was suppressed during the first 2?h. Chloroform was identified as the increasing species and dichloracetic acid was identified as the suppressed species. This study clearly shows that goethite, which is the predominant iron oxide of pipe deposits, alters both chlorine decay and DBP formation and should be considered when assessing water treatment plant operations and DBP monitoring site selection.     

Lime-Soda Softening Process Modifications for Enhanced NOM Removal

In this research, a number of process modifications to the lime-soda softening process were examined, including utilization of high Mg-content lime, addition of MgCl2, and the recycling of softening sludge, in order to improve the removal of natural organic matter (NOM) and reduce the formation of disinfection byproducts (DBPs). Jar test results showed that dissolved organic carbon (DOC) removal increased and trihalomethane (THM) formation was reduced as the magnesium in hydrated lime increased, and was directly correlated with the amount of magnesium removed from the system. However, a dolomitic quick lime hydrated under atmospheric conditions resulted in less effective DOC removal due to a lack of available Mg, and subsequently, less co-precipitation of Mg(OH)2-NOM complexes. The addition of MgCl2 to the raw water also increased DOC removal and reduced THM formation in both the presence and absence of softening sludge, with DOC removal increasing as softening sludge and magnesium dosages increased. As high as 43% removal of DOC was achieved at the stoichoimetric lime-soda ash dose in the presence of 457 mg/L sludge and 7.5 mg/L MgCl2, as compared to only 13% removal in the absence of sludge and MgCl2. The recycling of softening sludge had little or no effect on the hardness and the level of inorganic elements in treated water. The results presented here provide new approaches for improving DBP precursor removal during lime-soda softening without significantly increasing lime and soda ash dosage or the generation of waste sludge.     

Effects of Bromide Ion and Natural Organic Matter Fractions on the Formation and Speciation of Chlorination By-Products

The impacts of bromide concentration and natural organic matter (NOM) characteristics on the formation and speciation of disinfection by-products (DBPs) in chlorinated NOM fractions were investigated. A total of 20 bulk water NOM fractions with a wide range of specific ultraviolet (UV) absorbance (SUVA254) values were obtained from a source water employing XAD-8 or XAD-4 resin adsorption in completely mixed batch reactors. SUVA was not a good predictor of DBP [trihalomethanes (THMs), haloacetic acids (HAAs), and adsorbable organic halogens (AOX)] formation and speciation. The destruction in the UV254 absorbance from chlorination did not correlate with DBP formation at any bromide level. NOM moieties which do not absorb UV light at 254?nm significantly contributed to DBP formation. Mass balance calculations on halogens using THMs, HAAs, and AOX data indicated that significant amounts of DBPs (>54% of AOX) other than THMs and HAAs were formed in NOM fractions with 60–110?μg/L bromide concentration. The relative occurrence of such other halogenated by-products decreased with increasing bromide concentrations up to 500?μg/L level. NOM in the studied water was more susceptible to the formation of brominated THM species as opposed to brominated HAAs. At constant dissolved organic carbon concentration, chlorine dose and pH, increasing bromide concentrations in NOM fractions increased the total concentrations of DBPs and resulted in a shift toward the formation of brominated species. Further, increasing bromide concentrations increased the spectrum of detected species (i.e., occurrence of all nine HAAs) and provided a competitive advantage to THM and HAA precursors in NOM over precursors of other DBPs.     

Predicting the Formation of Chlorinated and Brominated By-Products

Although disinfection was one of the major public health advances in the last century and continues to be so in the twenty-first century, the disinfectants themselves may react with naturally occurring materials in treated water to form unintended by-products, which may themselves pose risks. This is of particular concern with regard to the use of chlorine. Generation of disinfection by-products (DBPs) has been shown to be a function of various factors including total organic carbon concentration, type of organic precursor, chlorination level, pH, temperature, reaction time, and UV-254 absorbance. Another factor affecting DBP formation is the presence and concentration of the bromide ion in the raw or finished water. Bromine substitutes for chlorine to produce bromine-containing homologues of the more familiar chlorine species. The current list of by-products targeted for regulation contains brominated and mixed bromine-chlorine species of total trihalomethanes and haloacetic acids. These are known to form in bromide-containing waters when chlorinated. To control chlorination DBPs therefore requires an understanding of the factors that influence their formation. This paper presents a model that can be used to predict the formation of chlorinated, brominated, and mixed species compounds based on initial chlorine concentration, chlorine consumption, bromide ion concentration, and pH. The model clearly shows that higher levels of bromide in the water favor the formation of brominated compounds. Brominated compounds also form faster than chlorinated compounds.     

Trihalomethane and Haloacetic Acid Disinfection By-Products in Full-Scale Drinking Water Systems

Trihalomethane (THM), haloacetic acid (HAA5), and total organic carbon (TOC) data provided by the Missouri Dept. of Natural Resources for drinking water treatment systems in the State of Missouri was analyzed for the years 1997–2001. These data indicated that a significant portion of systems exceeded the current regulatory limits of 80 and 60?μg/L for THM and HAA5 in these years. The vast majority of the treatment plants exceeding the regulatory limits were small plants with service populations less than 10,000 people. No significant temporal trend in either THM or HAA5 was noted for the years 1997–2001. This work suggests that the proposed use of a locational running annual average may have a significant effect on compliance. The use of chloramines (combined chlorine) versus free chlorine (HOCl/OCl?) as a residual disinfectant was shown to significantly reduce both THM and HAA5 in systems that treat their own water (primary systems), but did not have a significant effect in systems which purchase their water from primary systems (secondary systems). Comparison of finished water at the treatment plant versus in the distribution system suggested that a majority of THM and HAA5 may be produced within the plant as opposed to the distribution system. Hence, reducing these chlorinated disinfection byproducts within the treatment plant itself should be a key focus for achieving compliance, and supports Environmental Protection Agency disinfection byproducts compliance guidelines using enhanced coagulation.     

Particulate and THM Precursor Removal with Ferric Chloride

Pilot-scale experiments were performed to investigate the effectiveness of enhanced coagulation in removing particles and trihalomethane (THM) precursors from two surface source waters: California State Project water and Colorado River water. The removal of suspended particles and natural organic matter at various ferric chloride doses and coagulation pHs was assessed through source water and filter effluent measurements of turbidity, particle count, UV254, TOC, and THM formation potential. Overall, it was found that optimal removal of particles and THM precursors by enhanced coagulation with ferric chloride is obtained at high coagulant doses (>16 mg∕L) and low pH conditions. Generally, turbidity removal is more efficient and head loss is more moderate at ambient pH compared with pH 5.5. Additionally, filter effluent particle counts were found to be consistent with residual turbidity data. The removal of THM precursors by enhanced coagulation is significantly enhanced at pH 5.5 compared with ambient pH. The reduction in THM formation potential is consistent with the trends observed for the THM precursor removal data (i.e., UV254 and TOC data). Furthermore, specific UV absorbance was used to estimate the proportion of humic substances in the raw waters. Enhanced coagulation was found to be less effective for the source water with the lower specific UV absorbance.     

Impact of Booster Chlorination on Chlorine Decay and THM Production: Simulated Analysis

The effect of conventional and booster chlorination on chlorine residuals and trihalomethane (THM) formation in drinking water distribution systems was modeled using the EPANET hydraulic modeling software. The model results suggest that booster chlorination may allow utilities to meet disinfection goals better by carrying chlorine residuals to remote points in the distribution system while lowering the total mass of chlorine applied to the system. The model results suggest that booster chlorination may provide the greatest advantages to points in the distribution system located near storage tanks by providing a more consistent chlorine residual and possibly reducing THM formation. A new version of the EPANET model, the EPANET Multispecies model, was also used to compare chlorine decay due to reactions in the bulk fluid and reactions occurring at the pipe wall. The results suggest that chlorine decay due to wall reactions can be very significant at remote points in the distribution system. Additionally, if THMs are assumed to form primarily through reactions in the bulk fluid, use of the new EPANET Multispecies software allows for calculation of THM formation based solely on chlorine reactions in the bulk fluid rather than on overall chlorine decay.     

Infiltration Considerations for Ground-Water Recharge with Waste Effluent

Water reuse and ground-water recharge can be used to meet the growing demands for water, particularly in arid regions. Ground-water recharge using fresh water or treated wastewater is most often accomplished by infiltration from surface basins. The water percolates through the unsaturated soil region to an underlying aquifer for storage and future use. In the case of wastewater, additional treatment occurs as the effluent flows through the soil. The system hydraulics of recharge basins have been examined through a combination of field and laboratory investigations. These studies indicate that infiltration rates and soil aquifer treatment of wastewater are influenced by soil type and soil profile characteristics, surface clogging material, pond depth, and wetting∕drying cycle times. The surface-clogging layer was found to be susceptible to consolidation and to associated reduction in hydraulic conductivity under seepage forces.     

Exposure estimates to disinfection by-products of chlorinated drinking water

Exposure to disinfection by-products (DBPs) of drinking water is multiroute and occurs in households serviced by municipal water treatment facilities that disinfect the water as a necessary step to halt the spread of waterborne infectious diseases. Biomarkers of the two most abundant groups of DBPs of chlorination, exhaled breath levels of trihalomethanes (THMs) and urinary levels of two haloacetic acids, were compared to exposure estimates calculated from in-home tap water concentrations and responses to a questionnaire related to water usage. Background THM breath concentrations were uniformly low. Strong relationships were identified between the THM breath concentrations collected after a shower and both the THM water concentration and the THM exposure from a shower, after adjusting for the postshower delay time in collecting the breath sample. Urinary haloacetic acid excretion rates were not correlated to water concentrations. Urinary trichloroacetic acid excretion rates were correlated with ingestion exposure, and that correlation was stronger in a subset of individuals who consumed beverages primarily within their home where the concentration measurements were made. No correlation was observed between an average 48-hr exposure estimate and the urinary dichloroacetic acid excretion rate, presumably because of its short biological half-life. Valid biomarkers were identified for DBP exposures, but the time between the exposure and sample collection should be considered to account for different metabolic rates among the DBPs. Further, using water concentration as an exposure estimate can introduce misclassification of exposure for DBPs whose primary route is ingestion due to the great variability in the amount of water ingested across a population.     

Hydrophobicity and Molecular Size Distribution of Unknown TOX in Drinking Water

The analysis of total organic halogen (TOX) in drinking water indicates that a substantial amount of the halogenated compounds cannot be accounted for by known specific disinfection by-products (DBPs). The primary aim of this research was to characterize the hydrophobicity and molecular size distribution of the unknown halogenated DBPs using XAD resins and ultrafiltration membranes. The impact of membrane rejection on the size analysis of unknown TOX was also investigated using chlorinated fulvic acid. Six finished waters from different locations and treatment processes were collected and fractionated into various hydrophobicity and molecular size groups. The results showed that most unknown TOX was in the size range between 0.5?kDa and 10?kDa, but it could have a wide spectrum of hydrophobicities. Simple ultrafiltration was not always reliable as a characterization tool, as it was shown to reject a significant fraction of DBPs with molecular weight (MW) lower than the membrane cutoffs. Flushing with deionized water was effective in removing these low MW compounds from the ultrafiltration cell. A significant reduction in the apparent size of unknown TOX resulted when low MW DBPs were flushed out of the cell (comparing with classic parallel ultrafiltration). Coagulation of fulvic acid also significantly reduced the apparent size of unknown TOX formed by chlorine.     

Filariasis in northern Ghana: some cultural beliefs and practices and their implications for disease control

All four possible trihalomethanes (THMs) containing bromine and chlorine, as well as perchloroethylene (PCE), were evaluated for their ability to produce DNA strand breaks, alpha 2u-globulin rich renal deposits, and testosterone changes in male F-344 rats. Rats received daily equimolar doses (0.75 or 1.5 mmol/kg) of THMs or PCE (1000 mg/kg) in 4% Emulphor vehicle by oral gavage for 7 days. No significant DNA strand breaks were produced by any THM or PCE treatment. PCE treatment produced increased hyaline droplet formation in renal tubules. However, all THM treatments reduced or eliminated the appearance of renal hyaline droplets. All four THM treatments also produced a decrease in serum testosterone concentrations on day 7, which might account for decreased hyaline droplet formation. No significant increase in cell proliferation, measured by [3H]thymidine incorporation in vivo, appeared in this 1-week study.     

Acid-Gas Storage in a Deep Saline Aquifer: Numerical Sensitivity Study to Evaluate Parameter and Model Uncertainty

A modeling study is conducted to evaluate the sensitivity of acid gas evolution in a deep saline aquifer to expected variations of multiple geologic and engineering variables. Relative permeability hysteresis, aquifer heterogeneity variance, formation water salinity, permeability of caprock and leakage wells, injection rate, regional hydraulic gradient, and formation depth are evaluated as uncertain input parameters to a three-dimensional synthetic aquifer model with fully heterogeneous permeability. To understand the effect of conceptual model uncertainty on predicting gas flow and storage, permeability of the heterogeneous model is upscaled to equivalent permeability for three increasingly homogenized stratigraphic models: an eight-unit facies model, a three-unit depositional model, and a one-unit formation model. Two upscaling methods are used: a flow-based numerical method and an analytical averaging method. Over 120?years (20?years of injection and 100?years of monitoring), multiphase compositional simulation is conducted to model gas migration and trapping in the aquifer and its dissolution in the formation brine. Results suggest that among the variables evaluated, gas-relative permeability hysteresis, heterogeneity variance, and injection rate have the most significant impact predicting the total mobile gas in the storage system, whereas caprock permeability is the most important factor influencing the prediction of total gas leakage and thus the storage security. Over the simulation time scale, for the fixed amount of gas injected, regional hydraulic gradient, salinity, and formation depth have lesser impact on gas flow and storage predictions. Further, leakage through abandoned wells can occur when permeability of the wellbore is as low as 1?mdarcy (md), while caprock permeability becomes critical to storage security when it is more than 1×10-4??md, in which case significant leakage occurs during the monitoring phase. Compared to the predictions of the heterogeneous model, the greater the number of stratigraphic units in the upscaled models, the better its accuracy in predicting gas storage and plume sweep. However, the accuracy of the stratigraphic models depends on aquifer variance, upscaling method, and type of prediction outcome that is being evaluated.     

Incorporating Reservoir Transfer into Treatment Optimization Decisions

The Massachusetts Water Resources Authority (MWRA) supplies unfiltered water from two large surface water reservoirs to the metropolitan Boston area, as well as to three smaller communities in central Massachusetts [the Chicopee Valley Aqueduct (CVA) communities]. Quabbin Reservoir is larger than Wachusett Reservoir, and has traditionally been used to supplement the Wachusett during the summer period. Quabbin water is also of better quality, with lower reactive natural organic matter (NOM). The MWRA began to add chlorine at Wachusett in 1997, and a new facility for adding chlorine at Quabbin for the CVA was also started up in 2000 to meet primary disinfection regulations to meet pathogen inactivation. The reaction of chlorine with NOM produces undesirable disinfection by-products (DBPs). The absorption of ultraviolet light at a wavelength of 254 nm was identified in chlorine decay studies to be the most important raw water quality parameter for predicting chlorine decay and DBP formation. This technical note summarizes the chlorine decay model for Wachusett and Quabbin water. The model is extended to ozonation of Wachusett water for the future Walnut Hill treatment plant. The models allowed the development of a trigger using UV-254 to time the Quabbin transfer to optimize treatment results. It is believed that the model for disinfectant decay and the use of UV-254 as a trigger for water treatment decisions are generalized and applicable to other water utilities.     

Soil Salinity Modeling over Shallow Water Tables. II: Application of LEACHC

Root zone salinity is one of the major factors adversely affecting crop production. A saline shallow water table can contribute significantly to salinity increases in the root zone. A soil salinity model (LEACHC) was used to simulate the effects of various management alternatives and initial conditions on root zone salinity, given a consistently high water table. The impact of water table salinity levels, irrigation management strategies, soil types, and crop types on the accumulation of salts in the root zone and on crop yields was evaluated. There were clear differences in soil salinity accumulations depending upon the depth and salinity of the water table. In general, increasing water table depth reduced average soil profile salinity, as did having lower salinity in the water table. Among the four irrigation strategies that were compared, the 14-day irrigation interval with replenishment of 75% of evapotranspiration (ET) resulted in the lowest soil salinity. With a 4-day interval and 50% ET replenishment, a wheat yield reduction of nearly 40% was predicted after three years of salt accumulation. Soil type and crop type had minimal or no impact on soil salinity accumulation. Under all conditions, soil water average electrical conductivity increased during the 3-year simulation period. This trend continued when the simulation period was extended to 6 years. Under the conditions shown to develop the highest average soil salinity (high water table, low irrigation), an annual presowing irrigation of 125 mm caused a nearly 50% reduction in soil salinity at the end of the 6-year simulation period, as compared with the soil salinity given no presowing irrigation.     

A study of losartan, alone or with hydrochlorothiazide vs nifedipine GITS in elderly patients with diastolic hypertension

We conducted a randomised, double-blind, parallel design study comparing the efficacy and tolerability of the angiotensin II receptor antagonist, losartan, alone or with low-dose hydrochlorothiazide (HCTZ) to the dihydropyridine calcium channel blocker, nifedipine GITS (gastro-intestinal therapeutic system), in elderly patients (> or =65 years old) with a diastolic blood pressure (DBP) between 95 and 115 mm Hg. After a placebo wash out period, 140 patients were randomly assigned to receive either losartan 50 mg or nifedipine GITS 30 mg. Patients were evaluated at 4-week intervals during a 12-week treatment period. Patients receiving losartan had HCTZ 12.5 mg added and increased to 25 mg to reduce DBP <90 mm Hg. Patients receiving nifedipine GITS had their dose increased to 60 mg and 90 mg to reduce DBP <90 mm Hg. Efficacy, tolerability and quality of life were assessed during the 12 weeks on each regimen. Patients treated with the losartan regimen (n = 73) had reductions in trough sitting DBP of -10, -13, and -13 mm Hg after 4, 8, and 12 weeks of therapy, respectively. Patients receiving the nifedipine GITS regimen (n = 67) had DBP reductions of -14, -15, and -15 mm Hg, respectively. There were no significant differences in the DBP response between the treatment groups except at week 4 (P < 0.05). Similar reductions in systolic BP (SBP) between the two treatment groups were observed at all time points. The percentages of patients in the two treatment groups reaching goal DBP (<90 mm Hg or DBP > or =90 mm Hg with a reduction from a baseline of > or =10 mm Hg) were comparable (81% on the losartan regimen and 90% on the nifedipine GITS regimen). There were significantly more adverse events reported in patients receiving nifedipine GITS when compared to the losartan regimen (54% vs 36%, P < 0.05). A patient-reported symptom inventory also showed that swollen ankles was bothersome in significantly more patients treated with the nifedipine GITS regimen when compared to the losartan regimen (24% vs 5%, P = 0.001). Thus, in elderly patients with diastolic hypertension, a regimen of losartan alone or with HCTZ has similar efficacy to a regimen of nifedipine GITS with greater tolerability and less symptom bother due to swollen ankles.     

Porous Reactive Walls for the Prevention of Acid Mine Drainage: A Review

Abstract

Laboratory tests and field-scale demonstrations indicate that permeable reactive walls, designed to induce bacterially mediated sulfate reduction within aquifers, have the potential to prevent the discharge of acidic, metal-rich waters. Laboratory batch studies were conducted to determine optimal mixtures of organic materials. Column studies were conducted to evaluate the potential for sulfate reduction and metal sulfide precipitation under dynamic flow conditions at groundwater velocities similar to those observed in the field. These laboratory studies established that sulfate reduction and metal sulfide precipitation mechanisms result in decreases in the concentrations of sulfate and iron and other metals. In the column experiments, sulfate and Fe were removed from synthetic mine drainage water at rates of 500-800 mmol/day/m³. In a pilot-scale field study, test cells installed into an aquifer containing a plume of mine waste-impacted groundwater, induced sulfate reduction and metal-sulfide precipitation. Within a flow path of less than one metre sulfate reduction and metal sulfide precipitation reactions resulted in the removal of iron, and production of alkalinity to the extent that the acid generating potential of the plume water was removed. A full-scale porous reactive wall was installed at the same site in August 1995. Comparing water entering the wall to treated water exiting the wall; sulfate concentrations decrease from 2,400-4,500 mg/L to 200-3,600 mg/L and Fe concentrations decrease from 250- 1,300 mg/L to 1.0 - 40 mg/L. After passing through the reactive wall, groundwater is transformed from acid producing to acid consuming.     

Stress-management training for essential hypertension: a controlled study

Forty three patients with essential hypertension participated in a study on the effectiveness of stress-management training for essential hypertension. After 6-9 clinic and 48 self-measured readings of systolic and diastolic blood pressures (SBP and DBP), 22 patients were treated with a program based on education, relaxation, and problem-solving training; and another 21 patients were assigned to a waiting list control group. At post-treatment, mean reductions of clinic BP (17/13 mm Hg vs. 6.9/4.7 mm Hg for SBP/DBP), percentages of subjects who achieved at least a 5 mm Hg reduction (86/86% vs. 48/48% for SBP/DBP) and percentages of subjects who in addition achieved a normotensive level (59/68% vs. 29/14% for SBP/DBP) were significantly higher in the treated group than in the control group. Concerning self-measured BP, the effectiveness of the stress-management training was not so considerable (mean reductions of 3.6/2.4 mm Hg and percentages of subjects who achieved a 5 mm Hg reduction of 52/38% for SBP/DBP), but it was significant and maintained in a 4-month follow-up assessment (mean reductions of 4/2 mm Hg and percentages of subjects who achieved a 5 mm Hg reduction of 48/33% for SBP/DBP). It is suggested that stress-management training can be beneficial for treatment of essential hypertension.     

Effect of fluxing agents on reduction degradation behaviour of hematite pellets

During induration at a high temperature, a considerable amount of slag/melt phase forms inside the iron ore pellets, comprising SiO₂, Al₂O₃, CaO, MgO and FeO. After cooling, the slag phase solidifies and acts as an important bonding phase in the finished pellets and influences their room temperature as well as high temperature properties, especially reduction degradation. Fluxing agents play an important role in forming these bonding phases depending on the type and amount of flux. In the present study, the effect of different fluxing agents, namely, limestone, dolomite, magnesite and pyroxenite, on melt formation and microstructure during induration and on reduction degradation behaviour during reduction was examined. From the results, it was understood that to reduce the disintegration during reduction it is essential to increase the amount and distribution of bonding phases like silicates, which are more stable as compared to oxide phases like hematite. Acid pellets exhibited highest reduction degradation due to the presence of more hematite bonds and less silicate bonds. In limestone fluxed pellets, reduction degradation index dropped considerably with increasing CaO content due to the formation of more amount of bonding phase. Dolomite–pyroxenite pellets, on the other hand, showed lower reduction degradation index up to 0.4 basicity, and beyond that, higher degradation was observed due to the increased pore size, which resulted in poor strength of the reduced pellet matrix and hence more degradation. Low reduction degradation observed in pyroxenite and magnesite fluxed pellets could be due to the formation of magnesioferrite and silicate melt, which are more stable phases compared to hematite.