Nitrate Removal in Sulfur: Limestone Pond Reactors

The feasibility of using sulfur:limestone autotrophic denitrification (SLAD) pond reactors to treat nitrate-contaminated water or wastewater after secondary treatment was investigated with four lab-scale continuously fed SLAD ponds. The start-up period, temperature effects, and effects of different feed solutions were evaluated. With an influent concentration of 30 mg NO3?–N/L at an HRT of 30 days, the pond reactors had an overall nitrate removal efficiency of 85–100%. Effluent nitrite concentrations were <0.2 mg N/L in all tests. Aerobic conditions could result in a decrease of the SLAD pH of the pond by 2 to 3 units and a large increase in sulfate production ( ～ 1600–1800?mg-SO42?/L). Under unmixed (anoxic) conditions, the pH and sulfate produced were maintained at approximately 5.5 to 5.6 and 400–600?mg-SO42?/L, respectively, in all the SLAD ponds. Temperature affected the pond reactors adversely. By assuming that a first-order reaction occurred in a SLAD pond reactor, the temperature-activity coefficient, θ was found to be 1.068. Treatment of nitrate-contaminated surface water and wastewater using SLAD pond systems is feasible only if (1) the chemical oxygen demand (COD)/nitrate–N (COD/N) ratio is low (<1.2 with an initial NO3? concentration of 30 mg-N/L), (2) sulfur:limestone granules are not covered by sediment, and (3) sulfur-utilizing but nondenitrifying bacteria (SUNDB) are greatly inhibited due to the lack of DO in the pond systems. The SLAD ponds are not feasible for the treatment of raw wastewater or surface water if they contain high concentrations of organic matters due to the possible inhibition of sulfur-based autotrophic denitrifiers by heterotrophs (including heterotrophic denitrifiers). In addition, a high sulfate and low DO concentration as well as a low pH in the SLAD effluent of the pond (even when the pond is operated in an unmixed mode) also will limit the application of SLAD pond processes.     

Fenton 絮凝工艺去除废水中的有机物试验

为了研究废水中有机物的去除问题,针对某企业含有机物废水进行了对比试验,采用了Fenton 絮凝联合工艺去除废水中的COD（化学需氧量）和浊度,考察了初始pH值、H2O2投加量、H2O2与Fe2+投加物质的量比、反应时间、絮凝剂投加量以及絮凝剂投加时的pH值对COD以及浊度去除效果的影响。结果表明,采用最佳工艺参数组合后,浊度去除率和COD的去除率分别为99.32%和97.27%。     

Growth of Floating Aquatic Macrophytes in Alkaline Industrial Wastewaters

Ponds holding industrial wastewater can quickly develop algal blooms, which in turn results in high pH excursions. Such deterioration in water quality is experienced in Portland Aluminium's retardation pond. A covering of floating aquatic plants, such as Azolla filiculoides and Lemna minor, will reduce the light entering the water body, in turn reducing algal production and lowering pH levels. In the case of Portland Aluminium's retardation pond, the initial installation of such a system has to be established under alkaline conditions and in high fluoride concentrations (up to 10 mg∕L). The survival and growth of A. filiculoides and L. minor under alkaline conditions (pH levels of 7–9.5) and under different fluoride concentrations (0–10 mg∕L) were assessed in the laboratory and in field conditions. L. minor grew well under alkaline and high fluoride conditions in short-term laboratory tests, but appeared unable to compete with itinerant algae in the field. A. filiculoides survived only in media of pH 7 and 0-mg∕L fluoride in the short-term laboratory tests, but grew very well in the long-term field experiments. A. filiculoides was also observed to inhibit algal growth in the field. Both species absorbed fluoride. Fluoride concentrations in the plants rose and fell in relation to the fluoride concentrations in the pond, suggesting that the fluoride was readily desorbed and that the absorption itself was by a passive mechanism.     

Luminol-Based Enhanced Chemiluminescence Assay for Quantification of Peroxidase and Hydrogen Peroxide in Aqueous Solutions: Effect of Reagent pH and Ionic Strength

The effect of reagent pH and ionic strength was evaluated on the horseradish peroxidase (HRP)-luminol-p-iodophenol enhanced chemiluminescence assay. This assay was optimized for HRP and H2O2 quantification during enzyme-mediated remediation of groundwater or wastewater contaminated with phenolic chemicals. The maximum chemiluminescence intensity (ICLmax) and total area under the chemiluminescence intensity profiles were measured as a function of p-iodophenol concentration, reagent solution pH, and reagent ionic strength. ICLmax values were optimum at pH 8.5 and increased linearly with reagent ionic strength. Optimum chemiluminescence enhancement was produced at a p-iodophenol concentration of 0.3 mM under the reaction conditions. ICLmax values were linearly correlated with HRP and H2O2 concentrations within the ranges of 0.1–1 activity units/mL and 0.1–1 mM, respectively. Results indicate that the HRP-luminol-p-iodohenol enhanced chemiluminescence assay has a potential to be used for quantification of HRP activity and H2O2 concentration in aqueous solutions encountered in groundwater remediation or wastewater treatment scenarios.     

Effect of In-Lake Water Quality on Pollutant Removal in Two Ponds

An extensive field study examined pollutant removal in two regional wet detention ponds near High Point, N.C. Substantial differences in influent pollutant concentrations between the ponds caused significant differences in pond water quality and pollutant removal efficiency. In Davis Pond, influent fecal coliform and nutrient concentrations were high because of several large dairy farms in the watershed, resulting in hypereutrophic conditions as evidenced by high chlorophyll-a concentrations, high midday pH values and supersaturated midday oxygen concentrations. In Piedmont Pond, influent fecal coliform and nutrient concentrations were much lower, resulting in mesotrophic to slightly eutrophic conditions. Both ponds thermally stratified and developed an anaerobic hypolimnion. In Davis Pond, annual pollutant removal efficiencies for total suspended solids, volatile suspended solids, total organic carbon, total phosphorus, dissolved phosphorus, nitrate∕nitrite, total ammonia nitrogen, and total nitrogen were 56%, 32%, 15%, 41%, 54%, 16%, 2%, and 11%, respectively. In Piedmont Pond, annual pollutant removal efficiencies were 20%, 30%, 27%, 40%, 15%, 66%, ?64%, and 36%, respectively.     

Novel Design Concept for Facultative Ponds Using Rock Filters to Reclaim the Effluent

This paper presents a novel design concept for using rock filters as in-line natural media in waste stabilization ponds. A pilot-scale algae-rock-filter pond (ARP) system was investigated in parallel with algae-based ponds (ABPs) over a period of 6 months to evaluate the treatment efficacy of both systems. Each system entailed four equally sized ponds in a series and was continuously fed with domestic wastewater from Birzeit University. The removal rates of organic matter, nutrients, and fecal coliforms were monitored within each treatment system. The results obtained revealed that the ARP system was more efficient in the removal of organic matter [total suspended solids (TSS) and chemical oxygen demand (COD), 86% and 84%, respectively] and fecal coliforms (4log?) than the ABP system (81%, 81%, 3log?, respectively). The ARPs showed higher removal rates for ammonium and phosphorus (68.8% and 50.0%, respectively) compared with the ABPs (57.9% and 41.5%, respectively). The biogenic-aerated ARP option is a cost-effective and land-saving alternative with effluent quality suitable for restricted agricultural irrigation. The ARPs utilizing a new algae-biofilm design concept should be investigated at a large scale to enhance the information available to relevant decision makers, who are seeking sustainable on-site wastewater treatment alternatives.     

Nutrient removal from piggery effluent using vertical flow constructed wetlands in southern Brazil

Santa Catarina State, southern Brazil, has the greatest swine breeding activities of Latin America. Generally, the piggery wastewater is treated in pond systems that are able to remove organic material according to local environmental legislation. However, these systems do not remove nitrogen and phosphorus efficiently. This work deals with a post-treatment system, using vertical flow constructed wetlands. The experiment was conducted in a swine production farm which has 45,000 animals. Although the pond system was able to partially remove the content of nutrients, their concentration in the effluent was high for environmental disposal. A four-bed vertical flow constructed wetland pilot plant, using Typha spp., was built. The pilot plant operated for 280 days for beds 2-4 (sand 2). However, the experiments with beds 1-3 (sand 1) were stopped after 111 days of operation, when a reduction in the wastewater drainage was observed. The beds with sand 2 showed a 33% COD removal, and about 49% of nitrification was observed from 111 days until the end of the operation. PO(4)-P removal was 45% with a loading rate of around 1.36 g m(-2) d(-1).     

Storm Water Detention Ponds: Modeling Heavy Metal Removal by Plant Species and Sediments

Laboratory and field studies were conducted to elucidate heavy metal removal by three wetland grasses and sediments in storm water detention pond. The removal of heavy metals including Cd, Cu, Pb, and Zn was mediated by fluid-flow intensity in the reactors. The growth of plants and the removal rates of contaminants were plant species dependent. All three wetland grasses removed contaminants from the spiked nutrient solutions. A first-order kinetic model adequately represented the removal of contaminants by plants. The analyses of undisturbed sediment cores in detention pond revealed strong stratification of heavy metal concentrations at the sediment–water interface. A simple model that integrates heavy metal removal by aquatic plants and sediments in storm water detention ponds is proposed. The model provides an estimate of contaminant residence time which can be related to hydraulic residence time in storm water detention ponds.     

Effect of Nonsteady state H2O2 Tests on Oxygen Transfer Rate in Enhanced Biological Phosphorus Removal Process

A laboratory scale enhanced biological phosphorus removal process was operated in the University of Cape Town configuration to study the variations in alpha and oxygen transfer efficiency (OTEf) under different process conditions. As part of this investigation, process oxygen transfer parameters were determined using the steady state oxygen uptake rate (OUR) and the nonsteady state hydrogen peroxide addition (HPA) methods, as per the American Society of Civil Engineers guidelines. The results indicated that the oxygen transfer parameters [volumetric mass transfer coefficient (KLaf), oxygen transfer rate (OTRf), α and OTEf)] were higher when both methods were applied on the same day, compared to the subsequent period, when only the steady state OUR method was employed, under similar operating conditions. The difference in the oxygen transfer parameters appears to be due to the addition of H2O2 that generates reactive oxygen species in the nonsteady state HPA test. Based on the findings, it was concluded that the HPA test was not a suitable technique to measure oxygen transfer under process conditions. Further, a conceptual model hypothesizing the impacts of H2O2 addition on activated sludge process is presented.     

Stratification in Laboratory Simulations of Water Hyacinth Ponds

The technical and economical feasibility of using water hyacinth ponds for the treatment of wastewater is well established. However, various purification mechanisms operative in a pond have not been understood fully. In the present work, an attempt has been made to study stratification in four laboratory scale models of different depths operated continuously over a period of 4 months. It was concluded from this study that stratification did not occur in ponds. An attempt also was made to study the possible reasons for it. First, dense water hyacinth canopy stops radiation in excess of 90%. This prevents the growth of algae and subsequent increase in dissolved oxygen. Second, based on temperature profiles, thermal and density stratification also were found to be absent. Third, the secondary circulation in the ponds, induced because of influent and effluent being at different levels, also assists in checking the stratification. All these effects make a water hyacinth pond unstratified, which helps in uniform treatment throughout the depth and maintenance of designed hydraulic detention time.     

Fate and biological effects of polymeric MDI (4,4'-diphenylmethane diisocyanate and homologs) in small artificial ponds

The effects from a simulated accidental pollution event in a pond with polymeric MDI (4,4'-diphenylmethane diisocyanate and homologs) on different trophic levels of the aquatic ecosystem were investigated in small artificial ponds. Three 4.5-m3 volume ponds, interconnected with closable locks, were provided with natural lake sediment and ground water. Caged fish (rainbow trout, Oncorhynchus mykiss) were added to each pond, and the interconnecting locks were kept open to establish nearly identical physicochemical and biological conditions. At this stage, the ponds were isolated from one another and MDI was added at a dosage of 1 g/liter on top of the sediment of treated part of the first pond, 10 g/liter to the second pond, and 0 g/liter to the third pond (untreated control). Neither the applied monomer MDI nor its potential reaction product MDA (4,4'-diphenylmethanediamine) was detected in water or accumulated by fish. The MDI polymerized to inert polyurea on the sediment of the test ponds. This polymerization formed carbon dioxide, released as bubbles which floated to the water surface. Some carbon dioxide was solubilized in water and reduced the water pH of about 9 by 2.0 units as an average in the high-dosed pond and 0.7 in the low-dosed pond. This reduction caused some other minor changes in the physicochemical characteristics of the pond water. Neither application rate caused any direct effect on the pelagic community (phytoplankton, zooplankton, fish, macrophytes) of the test ponds. Some minor indirect effects caused by the production of carbon dioxide were observed in phyto- and zooplankton community structures. Also, an increase of macrophyte growth was noted. Organisms living in the untreated part of the sediment (macrobenthos) were affected as a result of physical obstructions in this habitat. These populations, however, regained densities equivalent to the control after some weeks, except for Bivalvia which have too long of a generation time for the test period of this study.     

Industrial Plant for Olive Mill Wastewater from Two-Phase Treatment by Chemical Oxidation

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 H2O2 (Fenton reaction). Tests have been made on an industrial scale. The final average value of chemical oxygen demand (COD) was close to 371?mg?O2?L?1 (%CODremoval = 86%, CODinitial = 2684?mg?O2?L?1), and the water produced can be used for irrigation or can be discharged directly into the municipal wastewater system for tertiary treatment.     

二价铜盐沉淀-树脂吸附处理氰化提金废水的研究

采用沉淀一离子交换联合工艺处理氰化提金废水,重点考察了CuSO4·5H2O用量及沉淀时间对各种离子沉淀率的影响,以及树脂的用量及吸附时间对各种离子综合去除率的影响。试验结果表明,当取CuSO4·5H2O理论用量的1．5倍、沉淀时间为60min时,CN^-、Fe、Zn离子沉淀率均可述到93％以上,而Cu离子沉淀率为50％左右。XRD分析表明,沉淀物主要由zn2[Fe（CN）6]、Cu2[Fe（CN）6]、CuCN及Zn（OH）2组成。吸附试验表明,当201×7树脂用量为5mL、废水体积为100mL、常温吸附75min时,氰化提金废水中CN^-及Cu、Fe、Zn离子的综合去除率分别可达到99．94％、71．23％、100％和99．95％,处理后废水中游离氰及铁、锌质量浓度达到了《GB8978-1996污水综合排放标准》一级排放指标。     

Enhanced Bioremediation of Fuel-Oil Contaminated Soils: Laboratory Feasibility Study

In this study, microcosm experiments were conducted to evaluate the effectiveness of (1) nutrients, hydrogen peroxide (H2O2), and cane molasses addition; (2) soil washing by biodegradable surfactant [Simple Green (SG)]; and (3) soil pretreatment by Fenton-like oxidation on the bioremediation of fuel-oil contaminated soils. The dominant native microorganisms in the fuel-oil contaminated soils after each treatment process were determined via polymerase chain reaction, denaturing gradient gel electrophoresis, and nucleotide sequence analysis. Results show that approximately 32 and 56% of total petroleum hydrocarbon (TPH) removal (initial concentration of 5,000?mg?kg?1) were observed in microcosms with the addition of nutrient and cane molasses (1,000?mg?L?1), respectively, compared to only 9% of TPH removal in live control microcosms under intrinsic conditions (without amendment) after 120 days of incubation. Addition of cane molasses would cause the increase in microbial population and thus enhance the TPH degradation rate. Results also show that approximately 61% of TPH removal was observed in microcosms with the addition of H2O2(100?mg?L?1) and nutrient after 120 days of incubation. This indicates that the addition of low concentration of H2O2(100?mg?L?1) would cause the desorption of TPH from soil particles and increase the dissolved oxygen and subsequent bioremediation efficiency in microcosms. Approximately 95 and 69% of TPH removal were observed in microcosms with SG (100?mg?L?1) and higher dose of H2O2(900?mg?L?1) addition, respectively. Moreover, significant increases in microbial populations were observed and two TPH biodegraders (Pseudomonas sp. and Shewanella sp.) might exist in microcosms with SG or H2O2 addition. This indicates that the commonly used soil remedial techniques, biodegradable surfactant flushing, and Fenton-like oxidation would improve the TPH removal efficiency and would not cause adverse effects on the following bioremediation process.     

In-Place Stabilization of Pond Ash Deposits by Hydrated Lime Columns

Abandoned coal ash ponds cover up vast stretches of precious land and cause environmental problems. Application of suitable in situ stabilization methods may bring about improvement in the geotechnical properties of the ash deposit as a whole, converting it to a usable site. In this study, a technique of in-place stabilization by hydrated lime columns was applied to large-scale laboratory models of ash ponds. Samples collected from different radial distances and different depths of the ash deposit were tested to study the improvements in the water content, dry density, particle size distribution, unconfined compressive strength, pH, hydraulic conductivity, and leachate characteristics over a period of one year. The in-place stabilization by lime column technique has been found effective in increasing the unconfined compressive strength and reducing hydraulic conductivity of pond ash deposits in addition to modifying other geotechnical parameters. The method has also proved to be useful in reducing the contamination potential of the ash leachates, thus mitigating the adverse environmental effects of ash deposits.     

Full-Scale Application of a Dynamic Model for High-Rate Anaerobic Wastewater Treatment Systems

High-rate anaerobic treatment systems are becoming increasingly popular to treat industrial wastewater containing large amounts of organic matter in the form of carbohydrates or proteins. Mathematical models of these systems can serve as tools for equipment sizing, process design, control and optimization, plant operation, and operator training. Several models for these plants have been proposed which have been validated and tested on laboratory-scale systems. Information on full-scale application of these models is not readily available. In this paper, a model only previously validated on laboratory scale was applied at full scale. The model was used to predict the behavior of two full-scale plants of different designs treating brewery wastewater under dynamic conditions. Influent and effluent liquid streams and gas flows were sampled over a 4 and 10 day period for the two plants, respectively. Limited characterization to just total carbon in feed over only four days was sufficient to predict the gas production rate or total volatile organic acid concentration in the effluent of the methanogenic reactor. Elaborate measurements over 10 days of feed characteristics including organic acid concentrations were important in obtaining good full-scale predictions of all variables that were modeled. Apart from the operating variables, the key parameter that required re-estimation for the full-scale system was the solids retention time in the methanogenic stage.     

Effect of Aeration on the Quality of Effluent from UASB Reactor Treating Sewage

The treatment of effluent of pilot- and full-scale upflow anaerobic sludge blanket (UASB) reactors operating at steady state was studied in an aeration-settling system. The fine pore submerged diffusers were used to aerate the effluent of UASB reactors under different operating conditions. Forty to 55% of the biochemical oxygen demand (BOD) and the chemical oxygen demand (COD) removal efficiencies were achieved by the direct aeration of the UASB effluent in the laboratory. The maximum removal efficiencies were achieved at 30?min hydraulic retention time (HRT) and a dissolved oxygen (DO) of 5–6??mg/L or high KLa (vigorous aeration). Batch experiments on nitrogen purging and the aeration of sulfides, volatile organic compounds (VOCs), and nonpurgeable organic carbons (NPOCs) were performed to ascertain the mechanism of BOD/COD removal. During aeration, BOD and COD were reduced by the stripping of H2S and VOCs and by the chemical oxidation of total sulfides and organic carbon. The stripping and chemical oxidation depended on the HRT and DO. The performance of a full-scale surface aeration system was compared to the performance of a pilot-scale diffused aeration system. Final sedimentation was effective only in removing the solids from the effluent of the aeration system. The results were confirmed by organic mass balance.     

Dissolved Oxygen-Stat Titration Respirometry: Principle of Operation and Validation

A method is presented to assess oxygen uptake rates which operates at constant dissolved oxygen concentration (DO). This method involves DO-stat titrations by controlled addition of a diluted H2O2 solution to a batch volume of activated sludge. The titrant flow rate is proportional to the biomass respiration rate, while the mass of H2O2 added is proportional to the oxidized organics. Classical batch respirometries (with and without gas flow, i.e., “open” and “closed”) were compared to the DO-stat technique using first NaSO2 as reducing chemical and then respiring aerobic biomass. An excellent correlation was found among estimates of oxygen consumption rate and short term yield coefficient by the three techniques. Inhibition by H2O2 was found to be negligible for biomass concentration as volatile suspended solids of ≥ 1.5–2 g?/L.     

羟基磷灰石复合材料对地下水中铀吸附去除研究进展

铀矿山尾矿库周边地下水在铀矿的风化、淋滤、渗漏等作用下,给地下水和人类带来长期的健康隐患。可渗透反应墙(PRB)作为一种原位修复技术,具有无动力运行、环境影响小和成本低等优点,已经在地下水污染修复中得到了应用。羟基磷灰石(HAP)因具有成本低、原料广泛、生物相容性等优点,成为去除地下水中铀废水的最具潜力介质材料。综述了羟基磷灰石在处理含铀废水中的影响因素,主要包括羟基磷灰石制备方法、改性方法,对含铀废水去除影响研究。并对羟基磷灰石除铀进行机理分析,包括羟基磷灰石形貌、铀溶液pH、共存阴离子等对铀的去除影响。羟基磷灰石(HAP)因具有成本低、原料广泛、生物相容性等优点,成为去除地下水铀的最具潜力介质材料。