Masoud Kayhanian

Pilot-scale high solids thermophilic anaerobic digestion of municipal solid waste with an emphasis on nutrient requirements

Abstract A pilot study was conducted to assess the biodegradable organic fraction of municipal solid waste (BOF/MSW) as a substrate in a high-solids anaerobic digestion process. Results obtained indicate that a typical BOF/MSW in the United States is deficient in most macro and micro-nutrients required for robust and stable digestion. The BOF/MSW was supplemented with nutrient-rich organic wastes such as wastewater treatment plant sludges, dairy manure, and synthetic chemical solutions to correct nutritional deficiencies. The combined addition of wastewater treatment plant sludge and dairy manure to a typical BOF/MSW significantly elevated the gas production rate and enhanced the process stability. Microbial nutrient requirements are identified and nutrient concentrations for stable operation are quantified.

Review of highway runoff characteristics: comparative analysis and universal implications.

This review interprets highway runoff characterization studies performed on different continents. The results are synthesized to discuss the historical trends, first flush effects of pollutants, pollutant form as dissolved vs. particulate, and to identify surrogate water quality parameters. The information presented in this review showed that: (1) variability has been observed in all quality parameters from each continent and among continents; (2) with a few exceptions the variability seems to be within the expected range; (3) inconsistent monitoring data as well as inconsistent quality assurance and quality control measures were reported among studies, which may be partially responsible for variability of water quality results; (4) compared with historic data, the concentration of total Pb decreased exponentially, which can mostly be credited to leaded gasoline phase-out regulation; (5) first flush effects of pollutants based on concentration have been reported consistently (however, mass first flush effects for pollutants have been reported inconsistently compared with concentration first flush effect); (6) most metal pollutants and phosphorus are present in both the particulate and dissolved forms; and (7) strong correlations were observed between TSS, TDS, TOC and iron (Fe) and 13 other constituents and water quality parameters (turbidity, O&G, TPH, DOC, TKN, EC, Cl, Cd, Cr, Cu, Ni, Pb, Zn).

The Use of Reflective and Permeable Pavements as a Potential Practice for Heat Island Mitigation and Stormwater Management

To help address the built environmental issues of both heat island and stormwater runoff, strategies that make pavements cooler and permeable have been investigated through measurements and modeling of a set of pavement test sections. The investigation included the hydraulic and thermal performance of the pavements. The permeability results showed that permeable interlocking concrete pavers have the highest permeability (or infiltration rate, ~0.5 cm s -1 ). The two permeable asphalt pavements showed the lowest permeability, but still had an infiltration rate of ~0.1 cm s -1 , which is adequate to drain rainwater without generating surface runoff during most typical rain events in central California. An increase in albedo can significantly reduce the daytime high surface temperature in summer. Permeable pavements under wet conditions could give lower surface temperatures than impermeable pavements. The cooling effect highly depends on the availability of moisture near the surface layer and the evaporation rate. The peak cooling effect of watering for the test sections was approximately 15–35?°C on the pavement surface temperature in the early afternoon during summer in central California. The evaporative cooling effect on the pavement surface temperature at 4:00 pm on the third day (25 h after watering) was still 2–7?°C lower compared to that on the second day, without considering the higher air temperature on the third day. A separate and related simulation study performed by the University of California Pavement Research Center (UCPRC) showed that full depth permeable pavements, if designed properly, can carry both light-duty traffic and certain heavy-duty vehicles while retaining the runoff volume captured from an average California storm event. These preliminarily results indicated the technical feasibility of combined reflective and permeable pavements for addressing the built environment issues related to both heat island mitigation and stormwater runoff management.

Permeability measurement and scan imaging to assess clogging of pervious concrete pavements in parking lots.

This paper describes a study that used permeability measurement along with physical and hydrological characteristics of 20 pervious concrete pavements in parking lots throughout California. The permeability was measured at five locations: the main entrance, an area with no traffic, and three separate measurements within a parking space at each parking lot. Hydrological and physical site characteristics such as traffic flow, erosion, vegetation cover, sediments accumulation, maintenance practice, presence of cracking, rainfall, and temperature data were also collected for each parking lot. These data were used to perform detailed statistical analysis to determine factors influencing changes in permeability and hence assessing possible cause of clogging. In addition, seven representative core samples were obtained from four different parking lots with permeability ranging from very low to very high. Porosity profiles produced from CT scanning were used to assess the possible nature and extent of clogging. Results showed that there is a large variation in permeability within each parking lot and between different parking lots. In general, the age of the parking lot is the predominant factor influencing the permeability. Statistical analysis revealed that fine sediment (particles less than 38 μm) mass is also an important influencing factor. Other influencing factors with lower significance included number of days with a temperature greater than 30°C and the amount of vegetation next to the parking lot. The combined scanned image analysis and porosity profile of the cores showed that most clogging occurs near the surface of the pavement. While lower porosity generally appeared to be limited to the upper 25 mm, in some core samples evidence of lower porosity was found up to 100mm below the surface.

Control of in-bed agglomeration by fuel blending in a pilot scale straw and wood fueled AFBC

Abstract Bed agglomeration in a pilot scale atmospheric fluidized bed combustor was controlled by blending wood into rice straw in concentrations of 50% wood or more and stoichiometrically holding reaction temperature at or below 800°C. At higher straw concentrations, agglomeration of the bed occurred over run times inversely proportional to the straw concentration in the blend. Bed agglomeration was preceded by a characteristic decline in bed pressure drop most likely related to combustion air channeling through the bed. Blend ash composition was not substantially affected until straw concentration decreased to 50% or below because of the four-fold higher ash concentration in the straw compared to wood. Blend ash base-to-acid ratio also was not substantially affected above 50% straw concentration, remaining essentially constant at 0.3, compared to the wood ash base-to-acid ratio of 1.1. Initial deformation temperature, as measured by standard cone test of the blend ash, increased from a minimum of 880°C for a 75% straw blend to 1120°C for a 10% straw concentration in the blend.

Size dependent elemental composition of road-associated particles

Stormwater particles often provide transport for metals and other contaminants, however only larger particles are effectively removed by typical best management practices. Fine particles and their associated constituents are more likely to reach receiving waters; this merits further investigation regarding the metal contribution of fine (d(p)<10 microm) and very fine (d(p)<1.5 microm) particles. Road associated particles were collected by vacuuming a road surface and by collecting highway stormwater runoff. A cell sorter was employed to sort road associated particles into four size ranges: 0.1-0.3, 0.3-0.5, 0.5-1.0, and 1.0-1.5 microm. These very fine particles, along with six particle size ranges (total range <2-63 microm) separated using a settling column, were analyzed for Al, Mn, Fe, Cr, Ni, Cu, Zn, and Pb using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Enrichment factors (EFs), calculated using Al as a basis to represent crustal contributions, were similar for the vacuumed road dust and the stormwater runoff. Fe and Mn were minimally depleted (0.1x) or near unity for all size ranges (Fe EF range 0.01-3.7; Mn EF range 0.02-10.6). Cr, Ni, Cu, Zn, and Pb were moderately (10x) to considerably (>100x) enriched for most size ranges; these metals were most enriched in the very fine fractions (max EF ~ 4900 in Zn, 0.1-0.3 microm). Based on this preliminary study, a cell sorter is an acceptable means of fractionating aqueous particles of diameter 0.1-1.5 microm. In spite of their minimal relative mass contribution, the very fine particles are environmentally relevant due to their mobility and enrichment in potentially toxic metals.

The impact of four design parameters on the performance of a high‐solids anaerobic digestion of municipal solid waste for fuel gas production

Abstract The impact of four design parameters on the performance of a pilot scale high‐solids anaerobic digestion process is evaluated and discussed in this paper. Results obtained from this study indicate that the rate of methane gas production was inversely proportional to the average feedstock particle diameter. Feedstock with various C/N ratios, ranging from 8 to 125, were fed into the reactor and an optimum C/N ratio, based on biodegradable carbon and total nitrogen, was found to be about 25 to 30. Biogas production increased with an increase of organic loading rate up to a rate of 7.5 g BVS kg‐1 active reactor mass?d. Organic overload occurred at 7.6 g kg‐1 and continued up to 11.5 g kg‐1 active reactor mass at which point the volatile fatty acids accumulation in the reactor reached an inhibitory limit and caused digester failure. Mass retention times of 30, 20, and 15 days were investigated, while the organic loading rate was kept constant at about 7 g BVS kg‐1 active reactor mass. Shorter MRTs re...

Comparative field permeability measurement of permeable pavements using ASTM C1701 and NCAT permeameter methods

Fully permeable pavement is gradually gaining support as an alternative best management practice (BMP) for stormwater runoff management. As the use of these pavements increases, a definitive test method is needed to measure hydraulic performance and to evaluate clogging, both for performance studies and for assessment of permeability for construction quality assurance and maintenance needs assessment. Two of the most commonly used permeability measurement tests for porous asphalt and pervious concrete are the National Center for Asphalt Technology (NCAT) permeameter and ASTM C1701, respectively. This study was undertaken to compare measured values for both methods in the field on a variety of permeable pavements used in current practice. The field measurements were performed using six experimental section designs with different permeable pavement surface types including pervious concrete, porous asphalt and permeable interlocking concrete pavers. Multiple measurements were performed at five locations on each pavement test section. The results showed that: (i) silicone gel is a superior sealing material to prevent water leakage compared with conventional plumbing putty; (ii) both methods (NCAT and ASTM) can effectively be used to measure the permeability of all pavement types and the surface material type will not impact the measurement precision; (iii) the permeability values measured with the ASTM method were 50-90% (75% on average) lower than those measured with the NCAT method; (iv) the larger permeameter cylinder diameter used in the ASTM method improved the reliability and reduced the variability of the measured permeability.

Biodegradability of the organic fraction of municipal solid waste in a high-solids anaerobic digester

Abstract Three methods were used to estimate the ultimate biodegradability of the organic fraction of municipal solid waste. These methods included: long-term batch digestion studies, measurement of lignin content, and chemostat studies. The ultimate biodegradability values obtained from these methods were compared to a field operation using a pilot scale, high-solids, complete-mix, thermophilic, anaerobic digestion process. The biodegradability obtained from the pilot study, at a mass retention time of 30 days, was approximately 83 and 81% of the estimated values obtained from the lignin content and the batch study, respectively. In addition, it has been shown that the contents of the biodegradable volatile solids affects the prediction of biogas production rate, the computation of the organic loading rate, and feedstock C N ratio.

Characteristics of highway stormwater runoff in Los Angeles: metals and polycyclic aromatic hydrocarbons.

Stormwater runoff from three highway sites in Los Angeles, California, was monitored, during the 2000 to 2003 wet seasons. Correlations among heavy metals, polycyclic aromatic hydrocarbons (PAHs), and storm characteristics were performed using datasets collected for 62 storm events. Statistical correlation analyses of the event mean concentrations (EMCs) and mass first-flush ratios (MFFs) with storm characteristics were conducted to determine if the first flush is related to site or storm characteristics. This study agreed with other highway runoff characterization studies, in that strong correlations were observed among the heavy metals and between heavy metals and total PAHs, and total suspended solids were well correlated with most heavy metals. Only antecedent dry days among storm characteristics were reasonably well-correlated with the EMCs of heavy metals and total PAHs, and dissolved and total metals exhibited similar MFFs, with approximately 30 to 35% of the mass being discharged in the first 20% of the runoff volume.