Majid Sartaj

Treatment of municipal landfill leachate using a combined anaerobic digester and activated sludge system.

The main objective of this study was to assess the feasibility of treating sanitary landfill leachate using a combined anaerobic and activated sludge system. A high-strength leachate from Shiraz municipal landfill site was treated using this system. A two-stage laboratory-scale anaerobic digester under mesophilic conditions and an activated sludge unit were used. Landfill leachate composition and characteristics varied considerably during 8 months experiment (COD concentrations of 48,552-62,150 mg/L). It was found that the system could reduce the COD of the leachate by 94% at a loading rate of 2.25g COD/L/d and 93% at loading rate of 3.37g COD/L/d. The anaerobic digester treatment was quite effective in removing Fe, Cu, Mn, and Ni. However, in the case of Zn, removal efficiency was about 50%. For the rest of the HMs the removal efficiencies were in the range 88.8-99.9%. Ammonia reduction did not occur in anaerobic digesters. Anaerobic reactors increased alkalinity about 3.2-4.8% in the 1st digester and 1.8-7.9% in the 2nd digester. In activated sludge unit, alkalinity and ammonia removal efficiency were 49-60% and 48.6-64.7%, respectively. Methane production rate was in the range of 0.02-0.04, 0.04-0.07, and 0.02-0.04 L/g COD(rem) for the 1st digester, the 2nd digester, and combination of both digesters, respectively; the methane content of the biogas varied between 60% and 63%.

PERFORMANCE OF FORCED, PASSIVE, AND NATURAL AERATION METHODS FOR COMPOSTING MANURE SLURRIES

Poultry manure slurry amended with sphagnum peat was composted by forced aeration (FA), passive aeration (PA) and natural aeration (NA) under high moisture conditions (76%). For each method three replicated piles were built and monitored over a period of three months. The compost piles had an initial volume of 5 m3 and were 1.2 m in height. Temperature profiles of replicated positions showed a high degree of similarity suggesting that the raw compost was uniform and the process was reproducible. An ANOVA test was carried out to compare the three treatment methods using the weighted average of temperatures inside each pile. The results showed that, for the selected configuration of aeration pipes and schedule, PA (1) had a higher process rate than NA; (2) provided adequate oxygen without the adverse effect of cooling as observed in the case in FA; (3) was less laborious than FA; (4) was more effective in conserving nitrogen than FA; and (5) maintained high temperatures (>55°C) for a longer time than the other two methods. FA and PA reached to a temperature of 15°C, 19 days (29% reduction) and 16 days (25% reduction) sooner than NA method.

Comparative Study of Static Pile Composting Using Natural, Forced and Passive Aeration Methods

Poultry manure slurry amended with sphagnum peat was composted by natural aeration (NA), forced aeration (FA) and passive aeration (PA). Compost piles were built in trapezoidal shape with a volume of 5 m3. A total of nine replicates, three for each treatment method, were built. A total of 231 thermocouples were used to establish a three-dimensional temperature regime in each pile.The results showed that, for the selected configuration of aeration pipes and aeration schedule, temperature drop occurred almost two weeks sooner in PA and FA process than NA process. Also, temperature inside PA and NA processes stayed above 55°C for a longer time than FA process. Both FA and PA methods were effective in providing more oxygen. Low O2 concentrations were measured at the bottom and middle of NA pile and middle of PA pile during the early stages of the process which is an indication of anaerobic conditions. A total mass reduction of 32 percent and volumetric reduction of 16 to 22 percent were observed. The mass red...

Influence Zone of Aeration Pipes and Temperature Variations in Passively Aerated Composting of Manure Slurries

Natural and passive aeration methods of composting under high initial moisture content condition (76%) were studied. Compost material consisted of poultry manure slurry as the waste and peat as the bulking agent. Piles were trapezoidal in section with an initial volume and height of 5 m3 and 1.2 m, respectively. Correlation factors of temperature readings of identical positions in replicate piles showed that the process was quite stable and reproducible. Influence zone of passive aeration pipes was limited to the interior portion of the bottom half of the pile. Temperature distribution inside the piles indicated that passive aeration pipes were effective in providing more air than natural aeration. Passive aeration process finished two weeks earlier than natural aeration process. The final product had a dark brown color and was rich in total nitrogen and phosphorus.

Enhanced biogas production by anaerobic co-digestion from a trinary mix substrate over a binary mix substrate.

The synergetic enhancement of mesophilic anaerobic co-digestion of trinary and binary mix of organic fraction of municipal solid waste (OFMSW) + primary sludge (PS) + thickened waste activated sludge (TWAS) as substrates was investigated through batch biological methane potential (BMP) and semi-continuous flow reactor tests. Cumulative biogas yield (CBY) yield for the binary mix of OFMSW:TWAS was 555, 580, and 660 mL/g volatile solids (VS)added for an OFMSW:TWAS ratio of 25:75, 50:50, and 75:25, respectively, which was 48, 78.5, and 140% higher than the calculated expected biogas (CEB) yield from the corresponding individual substrates. The trinary mixture of OFMSW:TWAS:PS at ratios of 25:37.5:375.5, 50:25:25 and 75:12.5:12.5 was able to produce 680, 710 and 780 mL/g VSadded, respectively, which was 25.5, 62.0 and 135.6% more biogas than the calculated expected biogas yield from the corresponding individual substrates. Cumulative methane yield (CMY) of trinary mixtures was also higher than the corresponding binary mixtures (20, 27, and 12 % increase for OFMSW:TWAS:PS at a ratio of 25:37.5:37.5, 50:25:25, and 75:12.5:12.5 compared to the binary mix of OFMSW:TWAS at a ratio of 25:75, 50:50, and 75:25, respectively). Methane content of the biogas varied from 54 to 57%. The results from semi-continuous flow anaerobic reactors under hydraulic retention times (HRT) of 15, 10 and 7 days supported the results of batch biological methane potential tests. The results were conclusive that enhancement in biogas production was noticeably higher from the co-digestion of trinary mix of organic fraction of municipal solid waste+ thickened waste activated sludge + primary sludge than the binary mix organic fraction of municipal solid waste+thickened waste activated sludge or thickened waste activated sludge+primary sludge with concomitant improvements in VS removal and biodegradability for tri-digestion of organic fraction of municipal solid waste, thickened waste activated sludge and primary sludge.

The toxicity effects of ammonia on anaerobic digestion of organic fraction of municipal solid waste

In this research the inhibitory effects of ammonia on the AD of synthetic OFMSW were examined under different total ammonia nitrogen (TAN) concentrations of 2,500, 5,000, 7,500, and 10,000mg/L and at pH levels of 7.5, 8.0 and 8.5 using a factorial experimental design and statistical analysis. Reduction in Cumulative Biogas Production (CBP) at a TAN concentration of 2,500mg/L was close to 10% for all 3 pH levels. For a TAN concentration of 10,000mg/L the percent reduction in CBP was over 80% for all 3 pH levels showing significant inhibition due to ammonia with neglible influence due to change in pH. However, pH played a more significant role for TAN concentrations between the above two levels, as at a TAN concentartion of 7,500mg/L, the percent reduction in CBP increased from 42.2% at a pH of 7.5 to 76.5% at a pH of 8.5. Regression analysis was used to estimate CBP and % reduction (%R) in CBP using a quadratic equation with pH and TAN as independant variables (R2=0.95 and 0.94). Methane produciton per g of COD removed was obsereved to vary from 264mL CH4/g CODd for control reactors at pH 7.5 down to 1mL CH4/g CODd for the reactor at pH of 8.5 which contained 10,000mg/L TAN. Results of gradual ammonia loading also showed that mesophilic bacteria could be adapted to a TAN concentration of up to 5,000mg/L at pH 7.5 through gradual TAN loading. At 10,000mg/L TAN CBP in reactors with gradual TAN loading was more than 1.9-3 times the CBP in reactors with abrupt TAN addition.

A comparison study of DRASTIC methods with various objective methods for groundwater vulnerability assessment

Groundwater vulnerability assessment is a measure of potential groundwater contamination for areas of interest. The main objective of this study is to modify original DRASTIC model using four objective methods, Weights-of-Evidence (WOE), Shannon Entropy (SE), Logistic Model Tree (LMT), and Bootstrap Aggregating (BA) to create a map of groundwater vulnerability for the Sari-Behshahr plain, Iran. The study also investigated impact of addition of eight additional factors (distance to fault, fault density, distance to river, river density, land-use, soil order, geological time scale, and altitude) to improve groundwater vulnerability assessment. A total of 109 nitrate concentration data points were used for modeling and validation purposes. The efficacy of the four methods was evaluated quantitatively using the Area Under the Receiver Operating Characteristic (ROC) Curve (AUC). AUC value for original DRASTIC model without any modification of weights and rates was 0.50. Modification of weights and rates resulted in better performance with AUC values of 0.64, 0.65, 0.75, and 0.81 for BA, SE, LMT, and WOE methods, respectively. This indicates that performance of WOE is the best in assessing groundwater vulnerability for DRASTIC model with 7 factors. The results also show more improvement in predictability of the WOE model by introducing 8 additional factors to the DRASTIC as AUC value increased to 0.91. The most effective contributing factor for ground water vulnerability in the study area is the net recharge. The least effective factors are the impact of vadose zone and hydraulic conductivity.

Assessment and comparison of PHCs removal from three types of soils (sand, silt loam and clay) using supercritical fluid extraction

ABSTRACT Supercritical fluid extraction (SFE) was applied to investigate the removal of petroleum hydrocarbons (PHCs) from contaminated soils. Per an initial set of tests for different extraction modes and time durations, the combination of 10 min static mode followed by 10 min dynamic mode, repeated for 3 cycles for a total time of 60 min resulted in the highest PHCs removal percentages. SFE experiments were performed at 33 MPa pressure and 75°C temperature to investigate the influence of soil texture and grain size. Three types of soils were formed and then were spiked with diesel fuel with a ratio of 5 wt%. Soil A, B and C had different particle sizes and were categorized as sand, silt loam and clay, respectively. Soil A (sand) which had the largest particle size resulted in the highest total petroleum hydrocarbon fractions (TPHF), sum of PHC F2, F3 and F4 fractions, removal percentage (90.4%) while soil C (clay) with the smallest particle size and the highest clay content led to the lowest TPHF removal percentage (47.4%). PHC F2 removal percentage for soil A (sand) was 27.3% greater than soil B (silt loam), and the removal efficiency for soil B was 20.4% higher than soil C (clay). While a similar trend was observed for the extraction of PHC F3, the extraction efficiency of PHC F4 for soil A, B and C were not statistically significant. Regarding soil A (sand), the extraction efficiency for PHC F2, PHC F3 and PHC F4 were 98.4%, 92.7%, and 50.2%, respectively. For soil C (clay), the removal efficiency of all PHC fractions were not statistically different. GRAPHICAL ABSTRACT

Simultaneous anaerobic oxidation/partial nitrification–denitrification for cost-effective and efficient removal of organic carbon and nitrogen from highly polluted streams

ABSTRACT Laboratory bench-scale anoxic/aerobic reactors with complete mix and continuous flow conditions were operated with high-strength synthetic wastewater to achieve simultaneous COD and nitrogen removal. High concentrations of organic carbon and nitrogen can be found in slaughterhouse, dairy, and food processing wastewaters, and also in some landfill leachates. Therefore, the goal of this study is to find a simple, efficient, reliable, cost-effective, and general solution for organic carbon and ammonia removal from streams with high influent concentrations of more than 5000 mg/L COD and 250 mg/L NH3–N. The highest COD (97%) and NH3–N (91%) removal efficiencies were obtained with initial COD and ammonia concentrations of 5211 mg/L and 262.8 mg/L NH3–N with volumetric loading rates of 11.26 kg COD/m3 d and 0.57 kg NH3–N/m3 d for COD and ammonia, respectively. Anaerobic oxidation is the main COD removal pathway in a simultaneous anaerobic oxidation/partial nitrification–denitrification (SAO/PND) system, and nitrogen removal significantly occurs via bacterial assimilation and partial nitrification–denitrification pathways. There are several advantages for this proposed SAO/PND system from a practical point of view, such as feasibility of simultaneous COD and nitrogen removal in a single reactor; simple operation; flexibility and practicality of this system as a general solution and cost effectiveness.