Journal of Environmental Engineering

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 $0.5\mathrm{kDa}$ and $10\mathrm{kDa}$ , 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.

This study reports sorption of the malodorant 2-methyl-2-propanethiol, commonly known as tertiary butyl mercaptan (TBM), to selected indoor materials. The phase distribution of TBM in gas-solid and aqueous-solid systems was evaluated using batch reactors. Sorbents used in the study included two carpets, two wallpapers, a soil, and granular activated carbon (GAC). Sorption was studied for gaseous and aqueous TBM concentrations spanning three orders of magnitude and contact times ranging from 1 to 28 days. The phase distribution data were plotted and fitted using linear and Freundlich relationships. Results indicated that all solids sorbed environmentally significant quantities of TBM, with the likelihood of producing concentrations above the odor threshold during subsequent remediation using mechanical ventilation. TBM retention by sorbents was greater from air than from water. The malodorant partitioned readily into wallpapers and slowly into the carpet materials. Sorption was nonlinear in the case of GAC and the nonlinearity appeared to increase with sorption contact time. GAC sorbed TBM strongly from both air and water.

A pilot-scale experiment was carried out to study the simultaneous removal of nitrogen and phosphorous from municipal wastewater by an innovative continuous-flow integrated biological reactor (CIBR) process. A three-phase separator was used in the CIBR process, which not only saved energy consumption of sludge returning, but also solved the sludge–gas separating problem. The optimal working condition was $2\mathrm{h}$ aeration, $1\mathrm{h}$ agitation, and $1\mathrm{h}$ settling, with an energy consumption of $0.23\mathrm{kW}\mathrm{h}∕{\mathrm{m}}^3$ . The average removal of chemical oxygen demand (COD), ammonia nitrogen $({\mathrm{NH}}_4^{+}–\mathrm{N})$ , total nitrogen (TN), and total phosphorus (TP) under the optimal conditions were 72.87, 75.23, 61.25, and 68.25%, respectively. The distributing rules of dissolved oxygen, pH, mixed liquid suspended solid, COD, ${\mathrm{NH}}_4^{+}–\mathrm{N}$ , ${\mathrm{NO}}_3^{-}–\mathrm{N}$ , TN, and TP in each phase of CIBR was studied. It was indicated that the appropriate condition was created for the simultaneous removal of nitrogen and phosphorus in the integrated reactor. The study demonstrated the feasibility of using CIBR process for simultaneous removal of nitrogen and phosphorus at the average temperature 12.2°C.

Biodegradability of chlorinated aliphatic (carbon tetrachloride) and aromatic (chlorophenol) compounds under acidogenic condition was investigated at pH of 5.0 to 5.5. Batch tests were used to evaluate biodegradability, adsorption capacity, and inhibitory effects of the chlorinated compounds on the fermentative microbial consortium. The biodegradability of carbon tetrachloride differed from that of the chlorophenols tested. Carbon tetrachloride was degraded to dichloromethane, and its adsorption onto the biomass was minimal. Inhibition of the acidogenic process was not observed for carbon tetrachloride at $10\mathrm{mg}∕\mathrm{L}$ . Chlorophenols (penta, tri, di, and mono) were not degraded at all, even after addition of vitamin supplements, increased incubation time, and increased primary to secondary substrate ratio. Chlorophenol removed from the aqueous phase by adsorption can be recovered from the acidogenic sludge. Pentachlorophenol was inhibitory to the acidogenic culture, whereas 2-chlorophenol was not. Microbial community analysis revealed the bacteria therein were primarily rumen and enteric bacteria. The results showed that it is possible to dechlorinate at least an aliphatic chlorinated compound under acidogenic conditions.

In recent years the application of partial nitrification techniques has been denoted as very promising. These methods are based on the oxidation of ammonia to nitrite and the inhibition of the nitratation using different strategies. In most cases, this inhibition causes an increase in the concentration of nitrite. However, the effect of high nitrite concentrations under low dissolved oxygen (DO) conditions on the nitrification process is not well understood. In this paper, the effect of ammonia, nitrite, and nitrate concentrations on the nitrification process under low dissolved oxygen concentrations were studied using respirometric techniques. Results showed that the specific oxygen uptake rate (SOUR) followed a Monod-type equation with respect to the DO concentration. The coefficient ${\mathrm{SOUR}}_m$ was constant with respect to the ammonia, nitrite, and nitrate within the tested concentrations; in addition, $K_{\mathrm{O}}$ was constant with respect to ammonia and nitrate but it increased linearly with the nitrite concentration, suggesting that nitrite was a competitive inhibitor of the SOUR. The inhibitory effect of nitrite was reverted by washing, in accordance with a competition model. From the data obtained using the open respirometer, the ratio between the oxygen consumption (OC) corresponding to each pulse of ammonia at different nitrite concentrations and the OC in the absence of nitrite $\left({\mathrm{OC}}_{\mathrm{O}}\right)$ was calculated. The experimental ratio $\mathrm{OC}∕{\mathrm{OC}}_{\mathrm{O}}$ was almost constant with respect to the nitrite concentration and it was close to the literature value. Finally, simulation results agree with the experimental data confirming that the proposed competition model represented adequately the inhibitory effect of nitrite on the respiration rate of ammonia-oxidizing bacteria.

This report assesses gas-phase mass transfer processes in landfills with respect to their influence on waste biodegradation. Gas-phase transport must dominate in many regions of the waste because aqueous-phase transport is restricted, the environment is largely unsaturated, and substantial quantities of gas are produced. Analysis of landfill gas and landfill gas condensate at four municipal solid waste landfills in the eastern United States demonstrated that both volatile fatty acids and microorganisms are transported in the gas phase. The heterogeneity, mass transfer limitations, and significant thermal gradients in waste environments imply that gas-phase processes can play crucial roles in waste decomposition, for example by regulating local pH and distributing trace nutrients. A conceptual framework describing these processes is presented. Implications for waste management, landfill design, energy production, air emissions, and anaerobic microbiology are discussed.

Effective integrated water management is a key component of the World Water Vision and the way in which aspirations for water equity may be realized. Part of the vision includes the promotion of sustainability of water systems and full accountability for their interaction with other urban systems. One major problem is that “sustainability” remains an elusive concept, although those involved with the provision of urban wastewater systems now recognize that decisions involving asset investment should use the “triple bottom line” approach to society, the economy, and the environment. The Sustainable Water Industry Asset Resource Decisions project has devised a flexible and adaptable framework of decision support processes that can be used to include the principles of sustainability more effectively. Decision mapping conducted at the outset of the project has shown that only a narrow range of criteria currently influence the outcome of asset investment decisions. This paper addresses the concepts of sustainability assessment and presents two case studies that illustrate how multicriteria decision support systems can enhance the assessment of the relative sustainability of a range of options when decisions are being made about wastewater asset investment.

The estimated atmospheric emissions of aircraft operations at a midsized Turkish airport (Adnan Menderes Airport, AMA) for the year 2004 are presented in this paper. The landing and takeoff (LTO) emissions of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides $\left(\mathrm{N}{\mathrm{O}}_{\mathrm{X}}\right)$ were calculated using the flight data recorded by the State Airports Authority Directorate General. Emission factors from the International Civil Aviation Organization Engine Exhaust Emission Databank were used for different aircraft operation modes such as take-off, climbout, approach, and taxi/idle engine conditions. Total LTO emissions from commercial aircrafts at AMA were estimated as $21\mathrm{t}∕\mathrm{y}$ for HC, $138\mathrm{t}∕\mathrm{y}$ for CO, and $197\mathrm{t}∕\mathrm{y}$ for $\mathrm{N}{\mathrm{O}}_{\mathrm{X}}$ . Boeing 737-800 type aircrafts have the biggest portions in total emissions (12% for HC, 18% for CO, and 35% for $\mathrm{N}{\mathrm{O}}_{\mathrm{X}}$ ). It is estimated that an increase of $1\min$ in taxiing time causes an increase of 4.2%, 4.6%, and 0.4% in the amount of HC, CO, and $\mathrm{N}{\mathrm{O}}_{\mathrm{X}}$ emissions, respectively. Estimations show that the full capacity of aircraft movements at AMA might cause annual emissions to be $176\mathrm{t}∕\mathrm{y}$ for HC, $\mathrm{1,184}\mathrm{t}∕\mathrm{y}$ for CO, and $\mathrm{1,306}\mathrm{t}∕\mathrm{y}$ for $\mathrm{N}{\mathrm{O}}_{\mathrm{X}}$ .

The rapid small-scale column test (RSSCT) has become a popular method for sizing granulated activated carbon (GAC) systems and columns for water treatment facilities. In this procedure, the GAC is ground and a specific size fraction is used for the RSSCT. Since GAC is produced and activated using different processes from different starting materials (e.g., bituminous, lignite, wood, etc.), the possibility exists that the extent of activation and, hence, the adsorptive capacity and surface reactivity may vary throughout the GAC particles. This would be the case if there were less activated inner cores in the GAC particles. If there is a variation in the sorption properties throughout the GAC particles, then grinding the GAC may result in smaller particles that have different properties than the bulk GAC. This study was carried out to test this commonly assumed hypothesis that the limited-sized ground particles represent the same adsorptive properties as the bulk GAC. Four activated carbons (manufactured from different source carbons) were studied. Gas adsorption tests determined the physical morphology, Boehm’s titrations checked the chemical nature of the surface oxides, and the Mohs hardness test was performed on all bulk GACs and ground fractions. No apparent differences were found in the total surface area, cumulative pore volume, or pore size volume of fractions generated by grinding activated carbons. In addition, the Boehm technique did not identify any significant differences in the chemical nature of the surfaces of the various size fractions of GAC. The Mohs hardness test did not indicate any variations in the hardness of the bulk GAC, the ground fractions, and the unground core. Based on the methods and materials used, the underlying assumption in the RSSCT analysis—that there are no variations in the different size fractions of the ground GAC—appears to be correct.

Development of stringent standards for the microbiological quality of the wastewater has necessitated a sensitive and efficient method for the enumeration of pathogens present in wastewaters. Standard methods are used all over the world for the identification of microbes by the public health engineers. However, this conventional method has serious problems, which are related to the long detection time required for turbid wastewaters and corresponding reduced isolation of the microbes. The Conventional method has been modified by omitting the concentration and blending steps, and named as the “Direct method.” The Direct method should be able to provide maximum possible recovery specifically for the turbid wastewaters. An existing sewage treatment plant was selected to carry out the study over a period of six months. Samples were collected from the various stages of treatment and analyzed for the isolation of Salmonella and Shigella using the Conventional method and the proposed direct method. The direct method required less time compared to the Conventional method. More importantly, the recovery of Salmonella and Shigella has improved by 105% and 276%, respectively, over the Conventional method. The consistent improvement in the recovery of the pathogens has been seen at various stages of the sewage treatment.