Approach to Control the Depth of Water in Basin Irrigation and Wetland Flooding

The controlled ponding of water over level terrain in basin irrigation or wetland flooding is described quantitatively as a three-phase process. During the first phase, water is applied at a known rate until ponding emerges at the time of ponding initiation. In the second phase, water continues to be applied at the same rate until a desired ponded depth is attained. In the third phase, water is applied to maintain the desired ponded depth during an arbitrarily long period. The desired ponded depth is maintained by adjusting the water-application rate to equal the infiltration rate plus the evaporation rate. The time of ponding, the ordinary differential equations (ODEs) governing cumulative infiltration during the second and third phases, and the water-application rate during the third phase are derived in this work using an extended Green-and-Ampt formulation of infiltration. Computational examples illustrate the solutions of the derived ODEs and their application in the control of basin irrigation and wetland flooding.     

Discharge and Suspended Sediment Transport during Deconstruction of a Low-Head Dam

In March of 2003, the 43?m wide, 2.2?m high St. Johns Dam (Sandusky River, Ohio) was breached to lower the water level in the reservoir. In November of the same year, the dam was removed in an effort to restore aquatic habitat and connectivity in the river. During both the breach and the dam removal, high resolution time series of discharge and suspended sediment concentrations were monitored 200?m downstream of the dam. Discharge and suspended sediment during the breach were not discernible from background values. In contrast, the dam removal resulted in a peak suspended sediment concentration of 59?mg/L and a peak discharge of 33.5?m3/s, which returned to background levels of 19?mg/L and 1.5?m3/s, respectively, approximately 8?h after the removal. The floodwave during the removal attenuated by 50% at the City of Fremont, 53?km downstream, illustrating the diffusive nature of the channel and the limited risk of flooding downstream. Levels of suspended sediment and discharge during the removal were comparable to subsequent discharge events. Spatial distributions of turbidity in and upstream of the dam pool and archived turbidity data from the City of Tiffin, 13?km downstream of the dam, suggest that sediments stored in the impoundment did not statistically enhance turbidity up to 2 years after the removal. Generally, the removal had a minor impact on water quality and posed no risk to public safety or to downstream aquatic habitats.     

复杂含锌矿物高效复合配位提取研究

针对复杂含锌矿物多金属伴生、物相组成复杂、碱性脉石含量高的特点,提出了第一配体为NH3、第二配体为氨三乙酸（NTA）,复杂含锌矿物复合配位提取新技术。在分析复杂含锌矿物物性特点的基础上,对单配体模型和复合配体模型中锌组分配位溶解过程进行了计算,确定了可配位溶解硅酸锌的配体,及复合配位体系的稳定常数,并利用NTA在等电点条件下溶解度最低原理,提出采用蒸氨―加酸工序从浸出溶液中回收NTA。研究证明,第一配体NH3仅能配位提取碳酸盐类含锌矿物,一定程度上限制了氨性配位浸出的广泛应用;NH4Cl-NH3-NTA（0.5 mol/L）复合体系的配位稳定常数为14.08,比NH4Cl-NH3体系配位能力提高4.62;NTA中氨基的N原子和羧基中的O原子与锌离子形成稳定的金属螯合物,促进传统的Zn(NH3)42+配合物向更为稳定的ZnNTA(NH3)2多配位配合物转变,锌浸出率提高113.4%;当浸出溶液pH调至1.30时,浸出溶液中NTA浓度降低至1.15 g/L,NTA回收率为96.0%。复杂含锌矿物高效复合配位提取新技术对于突破温和化学环境下多矿相有价金属的高效提取与利用具有重要指导意义。     

Characteristics and Reactivity of Algae-Produced Dissolved Organic Carbon

Algae (green, blue–green, and diatom) grown in inorganic media produced particulate and dissolved organic carbon (DOC). DOC produced by a green-alga contains 25% hydrophobic acids. DOC from all algae had specific ultraviolet absorbance values less than 2.0?m?1?(mg/L)?1. Algae-produced DOC was biologically labile; greater than 60% degraded in bioreactors within 5 days. The biodegradable material likely included carbohydrates, amino acids, and amino sugars, which were present in hydrophobic acid isolates. Chlorination of algal DOC formed disinfection by-products; DOC from the green alga, Scenedesmus quadricauda, produced chloroform [0.53?micromole?per?mg?carbon?(μmol/mg?C)], dichloroacetic acid (0.27?μmol/mg?C), and trichloroacetic acid (0.14?μmol/mg?C). This work complements other studies, which focused on algal total organic carbon (DOC and cellular material), and clearly demonstrates the importance of identifying algae-derived sources of DOC in water supplies and removing such DOC in water treatment plants prior to chlorination.     

Chemical-Enhanced Washing for Remediation of Soils Contaminated with Marine Diesel Fuel in the Presence/Absence of Pb

The effects of the operating conditions, the initial concentrations of marine diesel fuel (MDF) and the coexisting Pb in the soil, and the ethylene diamine tetra acetic salt (EDTA) in solution on MDF removal by sodium dodecyl sulfate (SDS) washing were extensively investigated with the aim of optimizing the process parameters and determining the MDF removal efficiency by SDS under different contamination conditions. The experimental results from batch tests indicated that the majority of MDF was removed by SDS in the first 2?h, and its optimal pH was nearly neutral. Increasing the SDS concentration linearly increased the MDF removal efficiency. At a given SDS concentration, the removal efficiency was dependent on the existing forms of MDF in soils, and the free phase of MDF was found to be more easily removed than the adsorbed phase. MDF removal by SDS was significantly reduced by the coexisting Pb in soils, which likely forms a complexation with SDS and thereby enhances the partitioning of MDF in the soil by the re-adsorption of released MDF onto the hydrophobic tails of the adsorbed SDS. EDTA alone, or with SDS, could remove MDF, but the remaining MDF in the contaminated soil after EDTA washing became more difficult to be removed by SDS. Therefore, the EDTA washing followed by SDS washing is not recommended for MDF removal.     

Effects of Primary Substrate Concentration on NDMA Transport during Simulated Aquifer Recharge

N-nitrosodimethylamine (NDMA) is known to be highly carcinogenic and is present in drinking water, wastewater, and a variety of foods. Because of its presence in chloraminated water at nanogram per liter concentrations, NDMA has become an emerging issue for reclaimed water which may be used for aquifer recharge or irrigation. This research investigated the fate of NDMA in two soil column systems used to simulate subsurface transport. One column system was operated under aerobic conditions with increasing primary substrate concentration where the biodegradable organic carbon (BDOC) in reclaimed water was used as the primary substrate. The reclaimed water content in the influent was increased from 0 to 25% in the column to increase the BDOC concentration. Negligible NDMA removal was observed at 0% reclaimed water and increasing the primary substrate in the influent resulted in NDMA removal suggesting that biodegradation of NDMA might be a cometabolic process. The effects of redox conditions on NDMA fate was studied by operating a second column system with 100% reclaimed water under anoxic conditions and then changing the conditions to aerobic. It was observed that NDMA removal was similar under both aerobic and anoxic condition, however, much lower effluent concentrations were observed under aerobic conditions. Under anoxic condition, a normalized mass removal rate of 254 ng NDMA/mg DOC was observed which increased to 273-ng NDMA/mg DOC under aerobic conditions. The majority of NDMA and substrate removal occurred in the first of three columns in series column under both aerobic and anoxic conditions. Normalized mass removal rates of NDMA after the first, second, and third columns were 372, 30, and 20 ng NDMA/mg DOC, respectively. Since the majority of dissolved organic carbon was also removed in the first column, NDMA biodegradation was consistent with cometabolic activity. Batch tests verified the biodegradation removal potential of NDMA. Addition of a methylotrophic substrate, methanol and an aromatic substrate, toluene, did not increase NDMA removal.     

Biodegradabilities of ethylenediamine-N,N'-disuccinic acid (EDDS) and other chelating agents

Biodegradabilities of chelating agents were tested with activated sludge. Ethylenediaminetetraacetic acid (EDTA) remained intact in the effluent even after acclimation for 100 days, but propanediamine-N,N'-disuccinic acid (PDDS) and nitrilotriacetic acid (NTA) were biodegraded after acclimation for 5 and 23 days, respectively. Optical isomers of ethylenediamine-N,N'-disuccinic acid (EDDS) had different biodegradabilities: SS- and RS-isomers were susceptible to biodegradation, but the RR-isomer was resistant. SS-isomer was degraded even by activated sludge without acclimation.     

Novel Hybrid Filter for the Treatment of Septic Tank Effluent

Intermittent sand filtration is a common and effective method for treating septic tank effluent. However, if the loading rate is too high, clogging and ponding of the sand filter surface layer can occur due to the accumulation of excessive biomass and the deposition of suspended solids. This ponding limits the practicality of sand filtration as it makes it necessary to take the filter out of service for maintenance. The objective of this study was to develop and test, on-site, a new hybrid filter system that would reduce the risk of clogging at an organic loading rate substantially greater than the maximum recommended loading rate for intermittent sand filters. The system comprised a 0.6?m deep horizontal flow biofilm reactor (HFBR) over a 0.85?m deep stratified sand filter. The HFBR consisted of a stack of 20 horizontal corrugated polyvinyl chloride sheets, at 32?mm vertical spacings. The sheets were arranged so that the wastewater flowed over and back along alternate sheets down through the stack. The main biofilm growth formed on these sheets. The hybrid filter was loaded with septic tank effluent from an office/garage complex at the rate of 206?L/m2?day for a period of 400 days in two phases. During the first phase, the effluent volume of 600?L/day was applied in 24 doses/day for 10?min/dose, and during the second phase in 6 doses/day for 40?min/dose. Biofilms in the HFBR substantially reduced the organic and suspended solids loads that reached the sand filter surface and allowed an average total biochemical oxygen demand (BODT) loading rate, based on HFBR plan area, of 37?g?BODT/m2?day to be applied to the system without clogging. This rate was substantially greater than the maximum recommended loading rate of 24?g?BODT/m2?day for intermittent sand filters. During both loading phases a BODT removal of 94% was achieved and nitrification was nearly complete. The average effluent BODT was 12±4?mg/L during both phases. The hybrid filter system appeared to perform better in terms of suspended solids handling and nitrification during the more frequent dosing phase. The hybrid filtration system offers a more compact alternative to intermittent sand filtration on its own with little risk of clogging.     

Comparison of SF6 and Fluorescein as Tracers for Measuring Transport Processes in a Large Tidal River

We present the first large-scale comparison of a fluorescent dye [fluorescein (C20H10O5Na2)] and a gas [sulfur hexafluoride (SF6)] as tracers of advection and longitudinal dispersion from a dual tracer release experiment conducted in the tidal Hudson River. At the beginning of the experiment, 36?kg of fluorescein and ～ 4.3?mol of SF6 were injected into the Hudson River at an averaged depth of 9.5?m, ～ 1?m above the bottom, near Hyde Park, N.Y. After injection, fluorescein distributions were surveyed for 4 days (until it became undetectable) and SF6 distributions were surveyed for 10 days. The dye resolves initial vertical mixing on the day of injection, and then net advection and longitudinal dispersion, whereas SF6 provides information on net advection and longitudinal mixing on larger spatial scales and longer time scales. Quantitative estimates of transport processes (net advection and longitudinal dispersion) calculated from the two methods are consistent for the first three days, and start to deviate on the fourth day when the signal-to-noise ratio of the dye deteriorated.     

Nitrogen Transformations during Soil–Aquifer Treatment of Wastewater Effluent—Oxygen Effects in Field Studies

Depth-dependent oxygen concentrations and aqueous-phase total ammonia and nitrate/nitrite ion concentrations were measured in the field during the infiltration of wastewater effluent. Measurements illustrated the dependence of nitrogen fate and transport on oxygen availability. Infiltration basins were operated by alternating wet (infiltration) and dry periods. During infiltration periods, ammonia was removed within the top few feet of sediments via adsorption. Biochemical activity rapidly eliminated residual molecular oxygen in the infiltrate, making the soil profile anoxic. During dry periods, oxygen reentered the basin profile and sorbed ammonia was converted to nitrate via nitrification. Oxygen penetrated to a depth of about 0.6?m?(2?ft) within the first few days of dry periods. At greater depths, oxygen levels increased more slowly due to a combination of slow transport kinetics and biochemical (nitrogenous) oxygen demand. During normal wet/dry basin cycles consisting of about 4 wet and 4 dry days, the local vadose zone remained anoxic at depths greater than about 1.5?m?(5?ft) below land surface. As a consequence, conditions for denitrification were satisfied in the deeper sediments. That is, the nitrate nitrogen produced in near surface sediments moved freely downward with infiltrating water where it encountered an extensive anoxic zone before reaching local monitoring or extraction wells. The relative importance of dissolved organics and sorbed ammonia as electron donors for denitrification reactions remains to be established.     

Evaporation, Unsaturated Flow, and Salt Accumulation in Multilayer Deposits of “Paste” Gold Tailings

Both the geotechnical and geoenvironmental performances of surface deposited “paste” mine tailings are strongly influenced by desiccation, rewetting after precipitation, as well as interlayer flow. All these processes strongly depend on unsaturated flow within the tailings. Modeling of small (0.15 m in diameter)- and large (1.7?m×1.7?m in plan)-scale tests on two-layer deposits of paste gold tailings showed that desiccation and interlayer flow can be reasonably modeled using one-dimensional unsaturated flow codes, if volume change and its effect on the water-retention curve are considered. Though significant cracking occurred during drying of the paste tailings, its influence on the rate of evaporation was minimal. In some of the tests, the accumulation of salt at the surface substantially suppressed the rate of evaporation. The transport of ions leading to the accumulation of salt is modeled using a one-dimensional contaminant transport code coupled to the unsaturated flow code. The results provide insight into the coupling between evaporation and the accumulation of salts at the tailings’ surface.     

Zeta Potential, Dissolved Organic Carbon, and Removal of Cryptosporidium Oocysts by Coagulation and Sedimentation

This study evaluated the removal of viable Cryptosporidium parvum oocysts and changes in zeta potential during alum coagulation and sedimentation. Experiments were designed to evaluate oocyst removal and oocyst zeta potential at three initial dissolved organic carbon (DOC) concentrations and a wide range of alum doses and coagulation pH values. The study showed that changes in the initial DOC concentration affected the zeta potential of Cryptosporidium parvum oocysts and the removal of oocysts. Oocysts did not appear to be removed by a charge neutralization mechanism under the conditions used in this research. Sweep flocculation appeared to be the primary removal mechanism at the lowest DOC concentration tested in this study. For the highest DOC concentration tested, optimal coagulation conditions for oocyst removal coincided with optimal coagulation conditions for natural organic matter (NOM) removal, suggesting that NOM played a key role in the interaction between oocysts and the aluminum hydroxide precipitate.     

Bioavailability Prediction of Polycyclic Aromatic Hydrocarbons in Field-Contaminated Sediment by Mild Extractions

Assessing the bioavailability of a group of polycyclic aromatic hydrocarbons (PAHs) coexisting in a field-aged contaminated sediment was examined using mild extractions by isopropanol- and ethanol-water solutions at concentrations of 5–100%, using extraction durations from 1?h?to?7?days. At a given solvent concentration, an initial rapid phase of PAH desorption was generally observed during the first 12?h, followed by a subsequent slower phase of desorption. A similar biphasic desorption was evident with increases in solvent concentration. PAH removal by various mild extractions was compared with PAH biodegradation by indigenous microorganisms. The removal of individual PAHs using 1-day 70% ethanol extraction was closely correlated to corresponding PAH removal via biodegradation, suggesting the possibility of using alcohol-water solution to simultaneously predict the bioavailability of multiple PAHs in aged sediments to indigenous microorganisms.     

Effect of Increasing Nitrobenzene Loading Rates on the Performance of AMBR and Sequential AMBR/CSTR Reactor System

A laboratory scale sequential anaerobic migrating blanket reactor (AMBR)/aerobic completely stirred tank reactor (CSTR) system was operated to investigate the effect of increasing nitrobenzene (NB) concentrations on the performance of AMBR/CSTR reactor system. The reactor system was operated at increasing NB loading rates from 1.93?to?38.54?g?NB?m?3?day?1 and at a constant hydraulic retention time of 10.38?days. In this study, chemical oxygen demand (COD) and NB removal efficiencies, variations of bicarbonate alkalinity (Bic.Alk.), total volatile fatty acid (TVFA), and total methane gases were monitored. COD removal efficiencies were 93–94% until a NB loading rate of 5.78?g?m?3?day?1 in the AMBR reactor. For maximum COD removal, the optimum NB loading rate and NB concentration were found to be 5.78?g?m?3?day?1 and 60?mg?L?1, respectively. COD removal efficiencies decreased from 94 to 87% and to 85% at NB loading rates of 1.93–28.90 and 38.54?g?m?3?day?1, respectively. COD was mainly removed in the first compartment. NB removal efficiencies also were approximately 100% at all NB loading rates in the effluent of the AMBR reactor. The maximum total gas and methane gas productions were found to be 2.8?L?day?1 and 1.3?mL?day?1, respectively, at a NB loading rate of 5.78?g?m?3?day?1. The TVFA concentration in the effluent of AMBR was low (17?mg?L?1) at a NB loading rate as high as 38.54?g?m?3?day?1. Overall COD removal efficiencies were found to be 99 and 96% at NB loading rates of 1.93 and 38.54?g?m?3?day?1, respectively, in a sequential AMBR/CSTR reactor system. In this study, NB was reduced to aniline under anaerobic conditions. Aniline removal efficiencies were 100% until a NB loading rate of 17.34?g?m?3?day?1 in aerobic CSTR reactor while aniline removal efficiency decreased to 90% at a NB loading rate of 38.54?g?m?3?day?1 in an aerobic reactor. In the aerobic step, aniline was mineralized to catechol. The contribution of aerobic step is not only the degradation of aniline, it may also increase the COD removals from 85 to 99% at a NB loading rate as high as 38.54?g?m?3?day?1.     

Swine Wastewater Treatment Using Submerged Biofilm SBR Process: Enhancement of Performance by Internal Circulation through Sand Filter

Pollutants removal from swine wastewater by a submerged biofilm sequencing batch reactor (BSBR) with internal circulation of liquor through a sand filter was studied. The variation of nutrient removal efficiencies with changes in volumetric circulation ratios and rates were determined. The reactor was operated under the following conditions: One cycle per day, hydraulic retention time of 15 days, average NH4–N loading rate of 55?g?m?3?d?1, and without supplemental external carbon source. System performance was enhanced by conducting internal circulation of liquor through the sand filter. When compared with the performance of a single BSBR without sand filter, nitrogen and phosphorus removal efficiencies were found to increase by 18% and over 33%, respectively. With a circulation rate of 170?L?h?1?m?3, and duration of 22 h (circulation ratio of 0.9), TOC, NH4–N, and total soluble inorganic nitrogen (as NH4–N plus NOx–N) removal efficiencies of 73, 97.8, and 85.6%, respectively, were achieved. The enhancement of nitrogen removal was attributed to the occurrence of denitrification in the sand filter during circulation of liquor. The denitrification rate was proportional to the volumetric circulation ratio per day, resulting in an average 15% NOx–N removal in the sand filter. Also, it was found that continuous circulation during the entire reaction phases could be one way to achieve better performance.     

Chronic hypertension, pregnancy-induced hypertension, and low birthweight

Menstrual and hormone patterns were investigated in 10 fertile women (median age 37, range 25-43 years) with locally advanced cervical cancer treated with neoadjuvant chemotherapy (CT). CT consisted of two cycles of high-dose cisplatin (CDDP, 40 mg/m2, Days 1 to 4) and bleomycin (B, 15 mg/m2, Days 1 and 8) separated by an interval of 21 days. Menstrual patterns before and during CT were recorded. FSH, LH, estradiol, and progesterone were assayed on the day that treatment was begun, after 2 and 4 days of CDDP administration, and weekly between and after the two cycles. Hormone assays during the first week of CT showed no significant change in hormone levels. After the first course of CT, five patients showed hypergonadotrophic amenorrhea and five patients maintained menses, two showing ovulatory and three showing follicular phase hormone patterns. After the second course of CT, one more patient become amenorrheic, and endocrine follow-up showed that two patients maintained hypergonadotrophic amenorrhea, four with hypergonadotrophic amenorrhea had a return of hormone levels to the follicular range of 7-9 weeks after, three maintained follicular phase hormone patterns until operation, and one ovulated. Gonadal dysfunction should be included among the side effects of high-dose CDDP and B regimens.     

Comparison of Continuous and Sequencing Batch Operated Biofilters for Treatment of Gas-Phase Methyl Ethyl Ketone

Although biofiltration has been used successfully to remove and biodegrade a wide variety of gas-phase organic contaminants generated by industrial facilities and environmental remediation efforts, the ability of conventional biofilters to maintain high removal efficiency during short-term, unsteady-state, elevated loading conditions is limited. A promising alternative for improving biofilter performance during transient elevated loading conditions while minimizing the disadvantages of conventional treatment technologies is utilization of adsorption packing media and implementation of sequencing batch operating strategies. In the studies described herein, a continuous-flow biofilter (CFB) and a sequencing batch biofilter (SBB) were operated for more than 300 days to treat a methyl ethyl ketone (MEK) contaminated gas stream. The packing medium for both biofilters consisted of activated carbon coated polyurethane foam cubes. Both biofilters exhibited stable long-term performance with greater than 99% removal of the influent 106?ppmv MEK concentration during “normal” loading conditions. To assess performance during transient loading conditions, on a regular basis the influent MEK concentration of each biofilter was temporarily increased by a factor of 10 to 1,060?ppmv MEK for a duration of either 45 or 60 min. Results are presented which demonstrate how the operational flexibility of SBB systems can be utilized to minimize or eliminate contaminant emissions from biofilters during unsteady-state loading conditions. The SBB was able to remove more than 99% of the influent MEK at a transient loading rate of 380?g?m?3?h?1 and 83% of the influent MEK at a transient loading rate of 760?g?m?3?h?1. In comparison, the CFB exhibited lower MEK removal efficiency.     

Numerical calculation of energy deposition by high-energy electron beams: III-B. Improvements to the 6D phase space evolution model

The phase space evolution model of Huizenga and Storchi, Morawska-Kaczyńska and Huizenga and Janssen et al has been modified to (i) allow application on currently available computer equipment with limited memory (128 Megabytes) and (ii) allow 3D dose calculations based on 3D computer tomographic patient data. This is a further development aimed at the use of the phase space evolution model in radiotherapy electrons beam treatment planning. The first modification regards the application of depth evolution of the phase space state combined with an alternative method to transport back-scattered electrons. This depth evolution method requires of the order of 15 times less computer memory than the energy evolution method. Results of previous and new electron transport methods are compared and show that the new electron transport method for back-scattered electrons hardly affects the accuracy of the calculated dose distributions. The second modification regards the simulation of electron transport through tissues with varying densities by applying distributed electron transport through similarly composed media with a limited number of fixed densities. Results of non-distributed and distributed electron transport are compared and show that the distributed electron transport method hardly affects the accuracy of the calculated dose distributions. It is also shown that the results of the new dose distribution calculations are still in good agreement with and require significantly less computation time than results obtained with the EGS4 Monte Carlo method.     

Trickling Filter Nitrification Performance Characteristics and Potential of a Full-Scale Municipal Wastewater Treatment Facility

The trickling filter solids contact water pollution control facility for the city of Ames, Iowa has successfully nitrified wastewater with trickling filters for the past decade. Both first stage, carbonaceous biochemical oxygen demand removing trickling filters (TFs) and second stage, nitrifying TFs (NTFs) remove significant quantities of ammonia from the wastewater. Based on operating data from January 1999 through December 2001, the average specific ammonia removal rate for the TFs was 1.5×10?4?kg?N/(d?m2). Most probable number testing confirmed the presence of nitrifiers in the top media layer of both stages of trickling filters. An experiment was performed whereby flows to the TFs and NTFs were varied to test ammonia removal capabilities of the facility. During the experiment, the TFs removed an average of 2.4×10?4?kg?N/(d?m2) and the NTFs removed an average of 1.5×10?5?kg?N/(d?m2) due to low loading. Data collected during the study varied with operating conditions. It was compared to and used to calibrate NTF models. An empirical design model poorly fit the data, and a theoretically based model could not be calibrated well with apparent ammonia removal rates. A best-fit equation, dependent on hydraulic loading and influent ammonia concentration (adjusted for recirculation), was regressed directly to the data and is useful for describing nitrification in the Ames WPCF TFs.     

Double-Pass Solar Collectors with Porous Media Suitable for Higher-Temperature Solar-Assisted Drying Systems

A high-performance solar collector suitable for a solar-assisted drying system was designed, fabricated, and tested. Solar-assisted drying systems consist of the solar collector array, auxiliary heater, drying chamber, and the air distribution systems. The solar collector was a double-pass solar collector and has upper and lower channels. The lower channel of the solar collector was filled up with porous media, which also acts as a storage medium. The outlet temperature and the performance of the system increased with the presence of the porous media. The collector width and length are 120 and 240?cm, respectively. The upper channel depth is 3.5?cm and the lower channel depth is 10.5?cm. The solar collector array consists of six solar collectors, arranged as two banks of three collectors in series. The collectors were joined in series using internal manifolding. A temperature of 90°C can be reached at a solar radiation level of 800?W/m2, ambient temperature of 30°C, and mass flow rate of 0.06?kg/s. The solar-assisted drying system was used for drying of oil palm fronds from moisture content of about 63% to moisture content of about 15%, for a drying time of about 7?h. The overall system efficiency is about 25%.