Methanogenic toxicity and continuous anaerobic treatment of wood processing effluents

Wood processing effluents contain different types of phenolic compounds, from simple monomers to high molecular weight (MW) polyphenolic polymers, that can inhibit wastewater treatment. This work presents a comparative study of the methanogenic toxicity produced by three wood processing effluents (hardboard, fiberboard and BKME (kraft mill effluent)) using Pinus radiata, Eucalyptus and Tepa as feedstock (the last one being a native Chilean tree species). This study evaluates the influence of non-adapted granular and adapted flocculent sludge on forest industrial wastewater treatment as well as continuous anaerobic biodegradation of hardboard processing effluent using the upflow anaerobic sludge blanket (UASB). The adapted biomass (flocculent sludge) did not show any lag-phase signs. The 50% IC (the concentration causing 50% inhibition of methanogenic activity) was 4.3 g COD-effluent (chemical oxygen demand (COD)-of the effluent)/l and 2.8 g COD-effluent/l for the flocculent sludge and the granular sludge, respectively. The UASB system worked at low organic load rates (0.1-0.4 g COD/l d) with the COD removal ranging between 10 and 30%, and color removal did not occur under anaerobic conditions due to high MW. Indeed, the MW analysis indicates the presence of phenolic compounds over 25,000 Da in the anaerobic effluent.     

Integrating biodegradation and electroosmosis for the enhanced removal of polycyclic aromatic hydrocarbons from creosote-polluted soils

This paper presents a hybrid technology of soil remediation based on the integration of biodegradation and electroosmosis. We employed soils with different texture (clay soil and loamy sand) containing a mixture of polycyclic aromatic hydrocarbons (PAH) present in creosote, and inoculation with a representative soil bacterium able to degrade fluorene, phenanthrene, fluoranthene, pyrene, anthracene, and benzo[a]pyrene. Two different modes of treatment were prospected: (i) inducing in soil the simultaneous occurrence of biodegradation and electroosmosis in the presence of a biodegradable surfactant, and (ii) treating the soils sequentially with electrokinetics and bioremediation. Losses of PAH due to simultaneous biodegradation and electroosmosis (induced by a continuous electric field) were significantly higher than in control cells that contained the surfactant but no biological activity or no current. The method was especially successful with loamy sand. For example, benzo[a]pyrene decreased its concentration by 50% after 7 d, whereas 22 and 17% of the compound had disappeared as a result of electrokinetic flushing and bioremediation alone, respectively. The use of periodical changes in polarity and current pulses increased by 16% in the removal of total PAH and in up to 30% of specific compounds, including benzo[a]pyrene. With the aim of reaching lower residual levels through bioremediation, an electrokinetic pretreatment was also evaluated as a way to mobilize the less bioaccessible fraction of PAH. Residual concentrations of total biodegradable PAH, remaining after bioremediation in soil slurries, were twofold lower in electrokinetically pretreated soils than in untreated soils. The results indicate that biodegradation and electroosmosis can be successfully integrated to promote the removal of PAH from soil.     

Removal of organic matter and nitrogen from river water in a model floodplain

A significant improvement in river water quality cannot be expected unless nonpoint-source contaminants are treated in addition to the further treatment of point-source contaminants. If river water is sprayed over a floodplain, the consequent water filtration through the sediment profile can simultaneously remove organic matter and nitrogen in the water through aerobic and denitrifying reactions. This hypothesis was tested using lysimeters constructed from polyvinyl chloride (PVC) pipe (150 cm long, 15 cm in diameter) packed with loamy sand floodplain sediment. Water was applied to the top of the lysimeters at three different flow rates (48, 54, and 68 mm d(-1)). Concentrations of NO3 and dissolved oxygen (DO), chemical oxygen demand (COD), and redox potential (Eh) in the water were measured as functions of depth after the system reached steady states for both water flow and reactions. At the rate of 68.0 mm d(-1), a reducing condition for denitrification developed below the 5-cm depth due to the depletion of O2 by organic matter degradation in the surface oxidizing layer; Eh and DO were below 205 mV and 0.4 mg L(-1), respectively. At a depth of 70 cm, COD and NO3-N concentration decreased to 5.2 and 3.8 mg L(-1) from the respective influent concentrations of 17.1 and 6.2 mg L(-1). Most biodegradable organic matter was removed during flow and further removal of NO3 was limited by the lack of an electron donor (i.e., organic matter). These results indicate that the floodplain filtration technique has great promise for treatment of contaminated river water.     

Optimization of Fenton's oxidation of chemical laboratory wastewaters using the response surface methodology

Establishing a treatment process for practical and economic disposal of laboratory wastewaters has become an urgent environmental concern of the Department of Chemical Engineering of the Universidade Estadual de Maringá (State University of Maringá), Brazil. Fenton and related reactions are potentially useful oxidation processes for destroying toxic organic compounds in water. In these reactions, hydrogen peroxide is combined with ferrous or ferric iron in the presence or absence of light to generate hydroxyl radicals (.OH). The feasibility of Fenton's reagent to treat waste chemicals from an academic research laboratory was investigated in this study. A response surface methodology was applied to optimize the Fenton oxidation process conditions using chemical oxygen demand (COD) removal as the target parameter to optimize, and the reagent concentrations, as related to the initial concentration of organic matter in the effluent, and pH as the control factors to be optimized. Maximal COD removal (92.3%) was achieved when wastewater samples were treated at pH 4 in the presence of hydrogen peroxide and iron in the ratios [COD]:[H2O2]=1:9 and [H2O2]:[Fe2+]=4.5:1. Under these conditions, it was possible to obtain simultaneously maximal COD removal and minimal chemical sludge after treatment, which is a residue that needs further processing.     

Application of lime and calcium hypochlorite in the dephenolisation and discolouration of olive mill wastewater

The application of hypochlorite for the removal of soluble COD, phenolic and polyphenolic like compounds, and other organic compounds responsible for the olive mill wastewater (OOWW) colour has been experimentally studied. After the OOWW filtration on a sand column, the effluent was subjected to a fast liming under optimal conditions. Lime application reduced polyphenols, COD and SS contents to half of their initial values but an important blackening of the treated OOWW was observed, especially when adding high concentrations of lime (10% (W/V) and 15% (W/V)).A second stage of treatment was applied using calcium hypochlorite. In this stage, removal of the studied compounds reached as much as 95% at higher concentrations, and particularly the colouring of OOWW which is generally difficult to eliminate was greatly reduced. The OOWW hypochloration acted through coagulation–flocculation and a rapid oxidation of the organic matter proceeded from the first 5 min. The kinetic study of the degradation of the waste polluting compounds from liming showed that Ca(ClO)₂ reacts similarly in the elimination of organic compounds, polyphenols, SS and colouration. The analysis of the organochloride compounds generated by the reaction between hypochlorite and the organic compounds showed that DDD, DDT and the heptachlor contents exceeded the values recommended by the International and European drinking water standards.     

高氨氮污水和高浓度有机废水综合治理

选用以曝气生物流化池(ABFT)技术为核心、辅助以物理化学方法的工业化技术,对兰州石化公司高氨氮污水和高浓度有机废水进行了处理。处理结果显示:外排废水监测项目中pH值、悬浮物、COD、BOD5、氨氮、石油类、硫化物、氰化物、挥发酚的平均浓度均低于污水综合排放标准(GB8978-1996)的一级标准,其中:氨氮值仅为0.412mg/L,COD值为63.87mg/L。对COD、氨氮、硫化物、挥发酚、悬浮物等的去除率达到90%以上,石油类和BOD5的去除率也达到75%以上,取得了良好的效果。     

The removal of lignin and phenol from paper mill effluents by electrocoagulation

This study aims to investigate the treatment of paper mill effluents using electrocoagulation. Removal of lignin, phenol, chemical oxygen demand (COD) and biological oxygen demand (BOD) from paper mill effluents was investigated at various current intensities by using different electrodes (Al and Fe) and at various electrolysis times (1.0, 2.5, 5.0 and 7.5min). It was observed that the experiments carried out at 12V, an electrolysis time of 2min and a current intensity of 77.13mA were sufficient for the removal of these pollutants with each electrode. The removal capacities of the process using an Al electrode were 80% of lignin, 98% of phenol, 70% of BOD, and 75% of COD after 7.5min. Using an Fe electrode the removal capacities were 92%, 93%, 80% and 55%, respectively. In addition, it was found that removal of lignin, phenol, BOD and COD increased with increasing current intensity. In the experiments carried out at different current intensities, higher removal can be explained through a decrease in intra-resistance of solution and consequently an increase at the transfer speed of organic species to electrodes. It was also found that Al electrode performs higher efficiency than Fe electrode except for COD removal. However, the time required for removal of BOD was more than that of COD. The results suggest that electrocoagulation could be considered as an effective alternative to paper mill effluents treatment.     

PERFORMANCE VARIATIONS OF COD AND NITROGEN REMOVAL BY VEGETATED SUBMERGED BED WETLANDS1

ABSTRACT: Vegetated submerged bed wetlands can supplement treatment of onsite wastewater systems. This study evaluated vegetation, media, and seasonal impacts on system performance in six meso scale rock plant filters with and without narrow leaf cattails (Typha augustifolia). Daily chemical oxygen demand (COD) reductions in planted cells averaged 85 percent and weekly total nitrogen (TN) reductions averaged 50 percent. Planted cells had 17 percent greater COD reduction and 76 percent greater TN reduction than unplanted cells, both significant differences. Media type affected COD reduction, particularly in unplanted cells. COD treatment in planted cells was highest for fine crushed limestone (87±13 percent) and least variable for coarse river gravel (85±11 percent). No significant difference in TN reduction was observed for different media types (48 to 51 percent range). Seasonal influences on treatment included a significant decrease during late fall and early spring and a significant increase with temperature. After a step increase in organic loading, treatment efficiency decreased sharply but returned to prior levels after an adaptation period of about one month. Planted cells not only exhibited higher treatment efficiency but also had a retarded organic matter breakthrough, appearing after three to seven times the period for a bromide tracer. This supports a hypothesis that retardation of contaminant movement through the treatment cells results in enhanced removal. These results support the use of rock plant filters, but demonstrate the need to account for performance variations in system design. (KEY TERMS: constructed wetlands; seasonal effects; subsurface flow; Typha augustifolia; onsite wastewater treatment; water quality.)     

Betaine removal during thermo- and mesophilic aerobic batch biodegradation of beet molasses vinasse: influence of temperature and pH on the progress and efficiency of the process

The key issue in achieving a high extent of biodegradation of beet molasses vinasse is to establish the conditions for the assimilation of betaine, which is the main pollutant in this high-strength industrial effluent. In the present study, aerobic batch biodegradation was conducted over the temperature range of 27-63°C (step 9°C), at a pH of 6.5 and 8.0, using a mixed culture of bacteria of the genus Bacillus. Betaine was assimilated at 27-54°C and the pH of 8.0, as well as at 27-45°C and the pH of 6.5. The processes where betaine was assimilated produced a high BOD(5) removal, which exceeded 99.40% over the temperature range of 27-45°C at the pH of 8.0, as well as at 27°C and the pH of 6.5. Maximal COD removal (88.73%) was attained at 36°C and the pH of 6.5. The results indicate that the process can be applied on an industrial scale as the first step in the treatment of beet molasses vinasse.     

Synthesis of biodegradable PVA/cellulose polymer composites and their application in dye removal

Environmentally sustainable composite films were synthesized using polyvinyl alcohol (PVA) and cellulose. Cellulose was extracted from the Agro-waste (sugarcane bagasse) using chemical pre-treatment followed by the acid-hydrolysis process. The composites were also used for the treatment of dye (Methylene blue; MB and Crystal violet dye; CV) and it was observed that the removal capacity of PVA/C was 70% for CV and 64.5% for MB dye. The biodegradation study of these composite films was also carried out using bacterial strains isolated from the marine waters of south Bengal. The biodegradation study of these polymer composites was characterized by FTIR, SEM, XRD, TGA, swelling properties, and weight loss. The results indicated that the PVA/C polymer showed a better rate of degradation (43%) than PVA (35%). Different loading parameters like pH, temperature, and inoculum dosage were studied to assess the degradation of the composite materials. Thus, biodegradable composite films were synthesized utilizing Agro-waste and had dye removal properties.     

Long-Term Monitoring and Prediction for Settlement and Composition of Refuse in Shanghai Laogang Municipal Landfill

Parameters about composition of refuse such as mass percentage of biodegradable matter, volatile solid, organic carbon, cellulose, total sugar, and settlement were monitored and analyzed in a large-scale experimental unit. The empirical formulas between composition and refuse age were established in terms of the data obtained from the experimental unit and verified by comparing with the corresponding parameters of refuse in the closed landfill units from 1991 until 1994 in the Shanghai Laogang Municipal Landfill. Furthermore, the long-term prediction for the composition of refuse was made, and it was predicted that the half-life is 7 to 11 years for biodegradable matter, 9 to 12 years for organic carbon or volatile solid, 7 to 16 years for cellulose, and 4 to 6 years for total sugar. In addition, a mathematical model, based on the mechanism of refuse biodegradation in the landfill, was developed to simulate the relationship between the settlement and the refuse age and manifests the secondary settlement potential. The mathematical model was proved not only to be reliable but also should be accurate for predicting the settlement of the landfill. The secondary settlement, which mainly results from the slow and gradual biodegradation of refuse, is linear with respect to the exponent of refuse age. Finally, according to the settlement model and empirical biodegradation formulas, it may be predicted that, 79.4% of biodegradable matter, 92.9% of total sugar, 72.7% of volatile solid and organic carbon, and 73.1% of cellulose will be biodegraded and that 79% of the maximum secondary settlement potential will occur before the Shanghai Laogang Municipal Landfill is in a high stabilization situation, i.e., approximately 21 years after final closure.     

Degradation of greenhouse twines derived from natural fibers and biodegradable polymer during composting

Commercial composting operations generally do not accept organic wastes with plastic twines from the greenhouse vegetable industry and the bulk of the waste materials ends up in landfills. The objectives of this paper are to identify environmentally compatible substitutes that could replace the current use of petrochemically derived plastic twines in greenhouse vegetable production, thus diverting them from landfills, and to assess the extent of their degradation via composting. Physical properties of the twines, including linear density, percent weight loss and tensile strength were monitored for the biodegradation tests. A pilot-scale composting trial was conducted in an in-vessel composting system. Results showed that the three biodegradable twine materials (cotton, jute and EcoPLA) could degrade readily in a composting environment within a reasonable time frame. Specifically, at the end of 105 days of composting, 85.3%, 84.8% and 81.1% of weight loss was observed for cotton, jute and EcoPLA, respectively. Furthermore, EcoPLA exhibited a slower decline in tensile strength with time, when compared to jute and cotton.     

GROUND AND SURFACE WATER QUALITY IMPACTS OF NORTH CAROLINA SANITARY LANDFILLS1

ABSTRACT: Ground and surface water quality monitoring data from 71 municipal sanitary landfills in North Carolina were analyzed to determine the nature and extent of current contamination problems and identify any common characteristics associated with this contamination. A total of 322 surface and 411 ground water quality records were analyzed using the SAS data system. Almost all the landfill records included inorganic and heavy metal analyses while approximately half of the records also included organic analyses by CC/MS. Our analysis indicates that landfills are having measurable impacts on ground and surface water quality, but these impacts may not be as severe as is commonly assumed. Statistically significant increases were detected in the average concentrations in ground water and downstream surface water samples when compared to upstream surface water samples. The largest percentage increases were observed for zinc, turbidity, total organic carbon, conductivity, total dissolved solids, and lead. Violations of ground water quality standards for heavy metals and hazardous organic compounds were detected at 53 percent of the landfills where adequate data existed. The moat common heavy metal violations were for lead (18 percent), chromium (18 percent), zinc (6 percent), cadmium (6 percent), and arsenic (6 percent) (percentage of landfills violating shown in parenthesis). The organic compounds that appear to pose the greatest threat to ground water are the chlorinated solvents (8 percent), petroleum derived hydrocarbons (8 percent), and pesticides (5 percent). A comparison of monitoring data from sanitary landfills and secondary wastewater treatment plants suggests that the concentrations of heavy metal and organic pollutants discharged to surface waters from these two sources are similar.     

Treatment and reuse of sewage sludge

Sewage sludge was treated using composting, fixed-bed and stirred anaerobic digesters. The treatment performance in terms of the physico chemical parameters, bacterial indicators and pathogenic forms were assessed. In addition, the biogas production rate was recorded in the case of anaerobic digesters. Composting of the sewage sludge increased its total solids from 39 to 93% after 6 weeks, while the reduction in organic matter was 40% and the total nitrogen and phosphorus contents increased by 22 and 30%, respectively. Complete removal of salmonellae and faecal coliforms occurred, so that the composted sludge could be used as a soil conditioner and fertilizer. The results of the anaerobic treatment indicated that an organic load of 4.8kg COD m–3 per day achieved the best operating conditions for either the stirred or fixed-bed digester. The mean percentage removals of COD, BOD, faecal coliforms, faecal streptococci and the biogas production rate for the stirred digester were 53, 53, 24 and 29% and 259 L kg–1 COD per day, respectively. The corresponding mean percentage removals and production rate for the experiments with a fixed-bed digester were 61, 62, 33 and 35% and 328 L kg–1 COD per day, respectively. Improvements in the BOD and faecal coliform reductions and the gas production rate of 17, 38 and 21%, respectively, were achieved due to the presence of media (Berl saddles) in the fixed-bed digester. The microbial content of the anaerobically treated sludge is too high to be used as a fertilizer, while that of the composted sludge is low enough for such use.     

焦化厂排水中微量有机污染物分析

本文采用XAD-2树脂／色谱／质谱(GC／MS)技术分析鉴定某焦化厂排水中的微量有机物。结果表明：焦化厂达标排放的废水中仍然含有芳香族及稠环类化合物如二苯乙醇酮、3,4-二氯-异氧杂萘邻酮、1,8-萘二甲酸酐,约占废水总有机碳含量的19．02％。特别是经氯氧化剂处理后生成许多卤代化合物,约占总有机碳含量的57．81％;其中包括毒性很大的二溴-氯甲烷、1-氯．1,2-二溴乙烷等,约占总有机物的7．54％。     

The application of potassium ferrate for sewage treatment

The comparative performance of potassium ferrate(VI), ferric sulphate and aluminium sulphate for the removal of turbidity, chemical oxygen demand (COD), colour (as Vis400-abs) and bacteria in sewage treatment was evaluated. For coagulation and disinfection of sewage, potassium ferrate(VI) can remove more organic contaminants, COD and bacteria in comparison with the other two coagulants for the same doses used. Also, potassium ferrate(VI) produces less sludge volume and removes more contaminants, which should make subsequent sludge treatment easier.     

BATCH REACTOR UNVEGETATED WETLAND PERFORMANCE IN TREATING DAIRY WASTEWATER1

ABSTRACT: Wetlands that treat holding pond effluent can be designed to utilize the pond storage capacity to allow flexibility in system management. Management of a wetland as a sequencing batch reactor can simplify operation and control detention times, but little performance data on such systems are available. The objective of this study was to evaluate the batch reactor wetland concept by quantifying removal of chemical oxygen demand (COD), total suspended sediments (TSS), total nitrogen (TN), ammonium (NH₄), nitrate (NO₃), total phosphorus (TP), and orthophosphate (PO₄) and by assessing the suitability of first‐order kinetics. Weekly samples were collected following batch loadings of wetland cells with high concentration or low concentration dairy holding pond wastewater during both fall and spring seasons. During three‐week batch periods without plants, overall mass removal averaged 54 percent for COD, 58 percent for TSS, 90 percent for TN, 72 percent for NH₄, ‐54 percent for NO₃, 38 percent for TP, and ‐8 percent for PO₄. Best fit, first‐order kinetic rate constant (k) and background concentration (C*) for COD varied by season, with k = 0.024/d and C*= 0 mg/l in fall and k = 0.056/d and C*= 200 mg/l in spring. Ammonium exhibited a consistent C*= 0 mg/l but had variable rate constants of k = 0.121/d for low concentration treatments and k = 0.079/d for high concentration treatments. Using first‐order kinetics was also appropriate for TN, with k = 0.061/d and C*= 0 mg/l for all loadings and seasons, but was not consistently appropriate for TP or PO₄. These results support the use of first‐order kinetics to describe treatment in batch reactor wastewater treatment wetlands without vegetation, perhaps during the establishment phase or in open water zones of vegetated wetlands. Further work is needed to assess the effects of vegetation.     

Solids and nutrient removal from flushed swine manure using polyacrylamides

Most of the organic nutrient elements (nitrogen and phosphorus) and carbon compounds in liquid swine are contained in fine suspended particles. Flocculation treatment with polyacrylamide (PAM) followed by screening is one the best methods to separate the liquid fraction from the solid fraction in swine manure, and thus to eliminate nutrient elements associated with solids. In this study, the efficiency of a synthetic polyacrylamide to treat swine manure was evaluated. After polymer treatment samples were sieved and the filtrated liquid was analyzed. TSS, VSS and COD concentrations in the liquid fraction were 2.17, 1.93 and 16.42 g/L respectively, accounting for 94, 94 and 77% removal percentages for TSS, VSS and COD using 30 mg/L of PAM.     

电化学氧化法处理高盐低COD污水研究

文章针对高盐、低COD难降解污水进行电化学氧化法降解有机污染物的研究和试验,介绍了电化学氧化法降解COD、氨氮的原理,探讨了试验对COD、氨氮、聚合物的去除情况,分析了装置的经济性能及试验去除污染物的影响因素。     

Chemical industry wastewater treatment

Treatment of chemical industrial wastewater from building and construction chemicals factory and plastic shoes manufacturing factory was investigated. The two factories discharge their wastewater into the public sewerage network. The results showed the wastewater discharged from the building and construction chemicals factory was highly contaminated with organic compounds. The average values of chemical oxygen demand (COD) and biochemical oxygen demand (BOD) were 2912 and 150 mgO₂/l. Phenol concentration up to 0.3 mg/l was detected. Chemical treatment using lime aided with ferric chloride proved to be effective and produced an effluent characteristics in compliance with Egyptian permissible limits. With respect to the other factory, industrial wastewater was mixed with domestic wastewater in order to lower the organic load. The COD, BOD values after mixing reached 5239 and 2615 mgO₂/l. The average concentration of phenol was 0.5 mg/l. Biological treatment using activated sludge or rotating biological contactor (RBC) proved to be an effective treatment system in terms of producing an effluent characteristic within the permissible limits set by the law. Therefore, the characteristics of chemical industrial wastewater determine which treatment system to utilize. Based on laboratory results engineering design of each treatment system was developed and cost estimate prepared.