Journal of Environmental Engineering

Mass balances for volatile organic compounds (VOCs) were added to a structured mathematical model of the high-purity oxygen activated sludge (HPO-AS) process. The model was sized to correspond to two large existing HPO-AS treatment plants. The stripping of ten different VOCs was modeled and compared to stripping from conventional air activated sludge process. The results show that the covered aeration tanks can reduce stripping by more than 90%, depending on the specific VOC. If biodegradation is considered, the HPO-AS process degrades more than the conventional process due to the higher liquid-phase concentrations that result because of reduced stripping. The increase in biodegradation depends on the VOCs degradability but should increase to nearly 100% for highly volatile but biodegradable VOCs.

During runoff transport, phosphorus (P) partitions between dissolved and particulate matter (PM) phases. PM-based P distributes across the particle-size distribution (PSD). This study investigates the transport and distribution for P and PM in runoff from a fully paved highway watershed in Baton Rouge, La. Eight events with discrete manual runoff sampling are studied. PSDs are modeled with a cumulative gamma distribution and PM-based P distributions are modeled with a Freundlich-type power law. P and PM fractions examined are dissolved, suspended, settleable, and sediment. Measured mass transport of these fractions is modeled based on flow-limited (zero-order) or mass-limited (first-order) delivery. Results demonstrate that transport of each fraction can be represented by these limiting categories, but fractions illustrate differing elution rates during the same event. Event-based signatures for PM or P are controlled by the fraction that dominates the transported mass. Even for small source area catchments such as roadways without complex flow patterns, where first-order transport should dominate, transport of P and PM fractions is not consistently first-order; exceptions are mainly dissolved and suspended fractions. A water quality volume (WQV) for 25 mm of runoff resulted in 100% capture for all fractions of seven events and significant bypass for all fractions of a single event with a 1-year return frequency. By contrast, a WQV of 5 mm of runoff resulted in significant bypass for most fractions for seven events and 100% capture for the single event of the lowest runoff volume.

Understanding storm-water runoff quality is required to develop effective urban storm-water runoff management for regions of semiarid climate. In this study, the quality of storm-water runoff from a semiarid, urban residential catchment, draining through separated storm-water sewers was investigated in 2006 and 2007. Water temperature, conductivity, pH, dissolved oxygen, and turbidity were continuously measured during 16 storm events. Storm-water runoff quality was characterized in terms of event mean values (EMVs), loads, and first flush (FF) loads and their relationships with rainfall characteristics. Discharge of total suspended solids (TSSs) is in general governed by the flow magnitude in storms and no significant relationships exist between the FF loads of TSS and rainfall intensity. The discharge of dissolved solids is independent of the flow magnitude. Strong FF effect for dissolved solids and weak FF effect for TSS were observed. This semiarid region provided no relationship between the EMVs of both TSS and conductivity and the antecedent dry period. This raises doubts on storm-water runoff being more heavily loaded with pollutants after a longer dry period in semiarid regions.

Fine particles entrained in storm-water runoff are likely to pass through storm-water treatment basins because of their slow settling velocities and the natural biotic and abiotic mixing processes common to ponds and basins. In Lake Tahoe, targeting fine particles $<20\mu \text{m}$ in diameter is critical to abating turbidity and phosphorus inputs disproportionately responsible for reducing the lake clarity and impacting regional water quality goals. Iron- and aluminum-based coagulant dosing has been commonly used in water and wastewater treatment plants for removal of fines, turbidity, and dissolved organic carbon. However, application of these coagulants for treating storm water is not common. This study used settling columns to show the feasibility of coagulant dosing to target fine particle removal from storm water in shallow treatment basins and wetlands. Coagulation reduced mean turbidity and phosphorus by 85–95% within 10 h of dosing, compared to 20 and 55% reductions in turbidity and phosphorus, respectively, for nontreated storm water over the same amount of time. To achieve equivalent treatment levels, an order of magnitude increase in time was required for the nontreated storm water. These results have important implications on approaches to treat storm water in the Tahoe Basin. First, these findings suggest that whereas most treatment basins and wetlands will not effectively remove fines and total phosphorus within a 24-h hydraulic residence time, those which utilize coagulant dosing should effectively remove fines and total phosphorus. Second, coagulant dosing relies on mechanical equipment such as pumps and flow meters. These equipments cannot accommodate normal variations in storm-water flow which can range over four orders of magnitude. Thus, to fully leverage the investment of this technology, modifications in hydrologic designs are necessary. We suggest equalization basins upstream of treatment basins to shift treatment from storm water entering a treatment complex to that leaving the equalization basin. This configuration buffers flows at the coagulant dosing location and increases the storage capacity of the storm-water treatment complex. Finally, given the paucity of available acreage in the Tahoe Basin and its high cost, coagulant dosing systems could be retrofitted to existing treatment basins and wetlands, enabling these treatment areas to be more effective in targeting phosphorus and fines, service drainage areas two or three times greater than currently, and reduce land area needed for treating storm water. We present a conceptual layout, a process and instrumentation diagram, and cost estimates to implement this technology at a larger scale. We believe that this technology should receive serious consideration for its application at a field or pilot scale where other potential issues can be further investigated and addressed.

The removal of toluene using ultraviolet (UV)-irradiated and nonthermal plasma (NTP)-driven photocatalysts system was investigated. Results indicated that the combination of photocatalyst with NTP (NTP-driven photocatalyst) had much higher toluene removal efficiency (TRE) and better photocatalyst durability, compared with UV-irradiated photocatalysis. The TRE was proportional to ozone consumption rate in the NTP-driven photocatalyst system, in which catalytic ozonation played a vital role in toluene decomposition. Its mechanism of toluene destruction differed from that of photocatalytic oxidation. The active oxygen from catalytic ozone decomposition was the dominant active species in the NTP-driven photocatalyst system.

This study investigated the potential of four full-scale oxidation ditches to accomplish enhanced biological phosphorus removal (EBPR). Despite the fact that none of the tested oxidation ditches were designed to perform EBPR, mixed liquors from all four ditches showed good specific phosphorus release and uptake rates, a typical characteristic of a typical EBPR biomass. The specific phosphorus release rates ranged from 0.042- to 0.254-mg P/mg VSS-d and the specific phosphorus uptake rates ranged from 0.023- to 0.125-mg P/mg VSS-d for the tested full-scale plants. The EBPR potential of one of the full-scale plants (Central Davis Sewer District) was further studied by changing the aeration patterns in the ditch. The mixed liquor in this full-scale plant exhibited good phosphorus release and uptake trends and dissolved phosphorus, as low as 1.26 mg/L, could be accomplished in the final effluent of this plant as a result of this optimization. The long-term feasibility of the EBPR in this full-scale was tested by running a bench-scale EBPR reactor, in which the anaerobic phase was replaced with aerated-anaerobic phase to simulate the mixed liquor environment that exists in Central Davis mixed liquor and, in general, in all oxidation-ditch-type activated sludge configurations. The bench-scale reactor showed consistent EBPR activity in the absence of an anaerobic environment and more than 85% phosphorus removal could be maintained in the reactor for more than 400 days. The intrafloc microanaerobic/anoxic zones, which may be present in the mixed liquor, did not seem to add to the EBPR efficiency under aerated-anaerobic conditions. Cloning and sequencing using Rhodocyclus specific forward primer RHC439 showed the abundance of organisms most closely falling in Rhodocyclaceae family but not related to Candidatus Accumulibacter phosphatis. Simultaneous 4^′-6–Diamidino-2–phenylindole (DAPI) staining and fluorescent in situ hybridization (FISH) using RHC439 probe clearly demonstrated the participation of polyphosphate accumulating organism (PAOs) targeted by RHC439 (i.e., in Rhodocyclaceae family). Microautoradiography assisted FISH using RHC439 further confirmed the participation of PAOs in Rhodocyclaceae family.

The effects of acetate and propionate on biological nitrogen and phosphorus removal in a plug-flow ${\text{A}}^2\text{O}$ process were evaluated in this study. The wastewater quality indexes and operation parameters were the same when different carbon sources were used. However, we observed no obvious effect of carbon source on nitrogen removal. Denitrifying phosphorus removal was found to play an important role in simultaneous nitrogen and phosphorus removal in anoxic reactors because almost the entire carbon source was used for polyhydroxyalkanoate (PHA) synthesis in anaerobic reactors, and there was no external carbon source left for heterotrophic denitrification. Propionate was found to be a more effective and energy-saving carbon source for biological nitrogen and phosphorus removal. In addition, the variations in the metabolic chemicals, such as phosphorus, PHA, glycogen, and oxygen, were lower when propionate was used than when acetate was used.

A mathematical model is developed and implemented to characterize the pickup of various liquid chemical contaminants by polyethylene-coated magnetic particles. The model and its associated experimental and analytical protocols were applied to a wide range of liquid chemicals in order to gain insights into the physical basis for the pickup phenomenon. The characteristics of the pickup isotherms range between “ideal” and “nonideal” behaviors that are reflected in the mathematical model by a single parameter, ${\alpha }_0$ , where ${\alpha }_0=1$ corresponds to ideal behavior and ${\alpha }_0>1$ corresponds to a departure from idealized behavior that is directly quantified by the magnitude of ${\alpha }_0$ . The parameter ${\alpha }_0$ is also related to the efficiency of pickup, and since most isotherms observed in the study deviate from ideality, the high efficiency of pickup observed in these systems has been attributed in part to this deviation. The proposed model and its associated experimental and analytical protocols demonstrate great potential for the systematic evaluation of the uptake of chemical contaminants using magnetic particle technology.

In this research we investigated the ability of cress seeds (Lepidium sativum L.) to grow in an aqueous media with metal toxicities. The toxicity of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn ions were examined in blank, nitrate $\left(\text{N}–{\text{NO}}_3\right)$ –, phosphate $\left({\text{KH}}_2{\text{PO}}_4\right)$ –, and saline (NaCl)–contaminated media. The acute toxicity of the tested metal ions in the blank media according to their IC50 (50% inhibitory concentration) values increased on the order of $\text{Pb}<\text{Fe}<\text{Co}<\text{Zn}<\text{Mn}<\text{Cr}<\text{Cu}<\text{Cd}<\text{Ni}$ . The effect of the different contaminations on the root growth of the cress seeds (Lepidium sativum L.) along with their separate and combined effects was investigated. Also, the changes in toxicity order were evaluated.

The performance of two flocculants on turbidity reduction was studied. The two flocculants were: a biopolymeric flocculant which was extracted from fruit waste and a commercial industrial flocculant. The effect of the flocculants’ average molecular weight on turbidity treatment, the treatment efficiency of both flocculants and the flocculants’ degradability were investigated. Response surface methodology was carried out using Box Behnken design to find the optimal pH, cation concentration, and flocculant dosage to maximize the turbidity reduction. The results showed that the maximum turbidity reduction by industrial flocculant occurs between pH 7.5 and pH 8.2, cation concentration between 0.02 and 0.06 mM, and industrial flocculant dosage between 6.5 and 8.0 mg/L. While with biopolymeric flocculant, maximum turbidity reduction occurred between pH 4.6 and pH 7.5, cation concentration between 0.60 and 0.95 mM, and biopolymeric flocculant dosage between 4 and 6 mg/L.

The sorption of inorganic arsenic species (arsenite and arsenate) from aqueous solutions onto steel-mill waste and waste filter sand, under neutral conditions, was investigated in this study. Additionally, the steel-mill waste material was modified in order to minimize its deteriorating impact on the initial water quality and to meet the drinking water standards. The influence of contact time and initial arsenic concentration was investigated using batch system techniques. To evaluate the application for real groundwater treatment, the capacities of the obtained waste materials were further compared to those exhibited by commercial sorbents, which were examined under the same experimental conditions. Kinetic studies revealed that waste slag materials are the most efficient in arsenic removal, reaching equilibrium arsenic sorption capacities in the range $47.6–55.2\mu \text{g}/\text{g}$ , while waste filter sand exhibited capacities of $25.4–29.8\mu \text{g}/\text{g}$ (for an initial arsenic concentration $C_o=0.5\text{mg}/\text{L}$ ). The higher iron content in the slag materials was considered to be responsible for the better removal efficiencies, and the specific arsenic removal efficiency was estimated to be $220\mu \text{gAs}/\text{gFe}$ . The specific arsenic removal efficiency of the second active substance found in waste filter sand, manganese, was estimated to be $115\mu \text{gAs}/\text{gMn}$ . Equilibrium studies revealed the occurrence of both chemisorption and physical sorption processes. All the waste materials exhibited higher performances for As(V). The highest maximum sorption capacity was obtained by waste iron slag: $4040\mu \text{g}/\text{g}$ for As(V). The waste materials reached the arsenic removal capacities of the examined commercial materials, suggesting the feasibility of their application in real groundwater treatment.

The Water Poverty Index (WPI) was created as an interdisciplinary indicator to assess water stress and scarcity, linking physical estimates of water availability with the socioeconomic drivers of poverty. This index has found great relevance in policy making as an effective water management tool, particularly in resources allocation and prioritization processes. Two conceptual weaknesses exist in the current index: (1) inadequate technique to combine available data and (2) poor statistical properties of the resulting composite. The purpose of this paper is to propose a suitable methodology to assess water poverty that overcomes these weaknesses. To this end, a number of combinations to create the WPI have been considered, based on indicators selection criteria, simple aggregation functions and multivariate analysis. The approach adopted has been designed for universal application at local scale. To exemplify the utilization of each alternative method, they have been piloted and implemented in the Turkana District (Kenya) as a case study. The paper concludes that the weighted multiplicative function is the most appropriate aggregation method for estimation of water poverty. It is least eclipsing and ambiguous free function, and it does not allow compensability among different variables of the index.

Outliers are an inevitable concern that needs to be identified and dealt with whenever one analyzes a large data set. Today’s water quality data are often collected on different scales, encompass several sites, monitor several correlated parameters, involve a multitude of individuals from several agencies, and span over several years. As such, the ability to identify outliers, which may affect the results of the analysis, is crucial. This note presents several statistical techniques that have been developed to deal with this problem, with particular emphasis on robust multivariate methods. These techniques are capable of isolating outliers while overcoming the effects of masking that can hinder the effectiveness of common outlier detection techniques such as Mahalanobis distances (MD). This note uses a comprehensive national metadata set on lake water quality as a case study to analyze the effectiveness of three robust outlier detection techniques, namely, the minimum covariance determinant (MCD), the minimum volume ellipsoid (MVE), and M-estimators. The note compares the results generated from these three techniques to assess the severity of each method when it comes to labeling observations as outliers. The results demonstrate the limitations of using MD to analyze multidimensional water quality data. The analysis also highlighted the differences between the three robust multivariate methods, whereby the MVE method was found to be the most severe when it came to outlier detection, while the MCD was the most lenient. Of the three robust multivariate outlier detection methods analyzed, the M-estimator proved to be the most flexible because it allowed for downweighting rather than censoring many borderline outlier observations.

Laboratory experiments and mathematical modeling were used to explore the dynamics of kaolinite and Pb in water-saturated porous media. Batch adsorption experiments were used to obtain the adsorption isotherms of Pb onto kaolinite and quartz sand. Both kaolinite and sand adsorbed Pb from water, but the adsorption capacity of kaolinite was about 30 times higher than that of sand. Saturated sand columns were used to examine the transport behaviors of Pb and kaolinite. The presence of kaolinite in the saturated porous media enhanced the mobility of Pb. The presence of Pb on kaolinite and grain surfaces, however, reduced the transport of kaolinite. Additionally, an experiment in which clean kaolinite was passed through sand contaminated with Pb indicated that mobile kaolinite could scavenge the absorbed Pb from the sand surface to facilitate Pb transport. Simulations from the Langmuir model and an advective-dispersive transport model matched well with the experimental data collected from the batch adsorption and column breakthrough studies.

Olive-oil production generates high and variable amounts of wastewaters from the olives and olive-oil washing (OMW), resulting to great environmental impact. These waters are normally stored in large holding ponds for evaporation during the summer. The present study examines the chemical-oxidation process using ferric chloride catalyst for the activation of ${\text{H}}_2{\text{O}}_2$ (Fenton reaction). Tests have been made on an industrial scale. The final average value of chemical oxygen demand (COD) was close to $371\text{mg}{\text{O}}_2{\text{L}}^{-1}$ ( $\mathrm{\%}{\text{COD}}_{\text{removal}}=86\mathrm{\%}$ , ${\text{COD}}_{\text{initial}}=2684\text{mg}{\text{O}}_2{\text{L}}^{-1}$ ), and the water produced can be used for irrigation or can be discharged directly into the municipal wastewater system for tertiary treatment.

Photoreduction of Reactive Brilliant Red X-3B in aqueous solution by ultraviolet irradiation/potassium borohydride/sodium bisulfite $\left(\text{UV}/{\text{KBH}}_4/{\text{NaHSO}}_3\right)$ was investigated. The effects of operational parameters including ${\text{KBH}}_4$ dosage, ${\text{NaHSO}}_3$ dosage, pH value, and temperature were studied. The reaction mechanism was also discussed. The preliminary results showed that UV and ${\text{KBH}}_4/{\text{NaHSO}}_3$ had a significant synergy for the decolorization. At the conditions of 6-mg ${\text{KBH}}_4$ , 250-mg ${\text{NaHSO}}_3$ , pH 6.0, and room temperature, highest color removal percentage was achieved. From the mechanism discussion, we could conjecture that the mechanism of photoreduction was mainly caused by the production of sulfur dioxide anion radicals, and UV irradiation played a vital role during the process.