改性TiO2/浮石光催化去除二级出水中有机物

为了实现城市污水厂二级出水的回用,将La3+、Fe3+共掺杂TiO2/浮石光催化用于二级出水中有机物的去除。在优化工艺条件下,该方法对TOC的去除率为49.0%,对UV254的去除率为76.5%;出水BDOC/DOC值大幅度提高,由最初的0.21提高到0.56,增加了出水的可生化性;二级出水中存在着影响光催化去除有机物的因素,其中阴离子对有机物的去除有一定的抑制作用;光催化反应在通过O3强化后对有机物的去除率得到提高,TOC的去除率达到75.0%,光催化和O3氧化对有机物的去除具有协同效应;随着光催化反应次数的增加,催化剂活性有下降趋势,使用10次后TOC去除率下降到第一次使用时的16.7%,再生能够使催化活性恢复到使用前的95%,催化剂在使用15次以内稳定性较好。     

The cytotoxic and genotoxic potential of surface water and wastewater effluents as determined by bioluminescence, umu-assays and selected biomarkers

Two bacterial tests employing Photobacterieum phosphoreum (Microtox bioluminescence test) and Salmonella typhimurium TA 1535 pSK1002 (umu-assay) were evaluated to estimate the cytotoxic and genotoxic potential of water samples from the selected rivers in Germany as well as the primary and secondary effluents of some sewage treatment plants. Rainbow trout (Onchorynchus mykiss) were exposed to different concentrations (20-40%) of secondary effluent in the model online aquatic monitoring plant WaBoLu-Aquatox. The toxic potential of water samples from the exposure tanks was determined in two prokaryotic test systems and the biomarkers acethylcholinesterase (AChE) activity in muscle tissue and DNA unwinding assay in liver tissue of fish. Samples from the tested rivers showed no inhibition of the bioluminescence of P. phosphoreum or growth of umu-bacteria. Only primary effluent samples from the treatment plants at the Saale River inhibited the light emission or the growth of test bacteria by more than 20%. The induction ratio of umu-bacteria was in most of the river samples less than the threshold for genotoxicity (IR < 1.5). Only some samples from the Saale River, especially at sites downstream of secondary effluents caused genotoxic responses in the umu-assay. Samples of primary effluents contained the greatest genotoxic potential up to GEUI = 6 which was not detectable in samples of secondary effluents. A concentration range 20-40% secondary effluent inhibited AChE activity in muscle tissue and significantly increased DNA fragmentation in liver tissue of rainbow trout. In contrast, no cytotoxic or genotoxic responses in the umu-assay were caused by water samples. Both bacterial methods can be successfully used to analyse the cytotoxic and genotoxic response of industrial and domestic wastewater and to estimate the effectiveness of sewage treatment units. However, because of their low sensitivity and high susceptibility, they are not reliable as a single test for the detection of cytotoxicity and genotoxicity in surface water. The application of prokaryotic tests systems with biomarkers such as AChE activity and DNA fragmentation in different tissues of test organisms seems to be a useful combination for the assessment of cytotoxic and genotoxic potential in surface water and secondary effluent.     

In situ and laboratory bioassays to evaluate the impact of effluent discharges on receiving aquatic ecosystems

Effluents are a main source of direct and often continuous input of pollutants into aquatic ecosystems with long-term implications on ecosystem functioning. Therefore, the study of the effects of effluent exposure on organisms, populations or communities within the framework of impact assessment has a high ecological relevance. The aim of this study was to assess the toxicological impact of two effluents, one household wastewater treatment effluent (Effluent 1) and one industrial effluent (Effluent 2), on the receiving aquatic ecosystem using two test species under both in situ and laboratory conditions. Zebra mussel (Dreissena polymorpha) and common carp (Cyprinus carpio) were exposed under laboratory conditions in an online monitoring flow-through system (receiving different concentrations of Effluent 2) and under in situ conditions along the pollution gradient established by these two effluent discharges. Bioassays focussed on growth and condition related endpoints (i.e. condition, growth, lipid budget), since these are key functional processes within organisms and populations. Under laboratory conditions, increasing concentrations of the industrial effluent (Effluent 2) had a negative effect on both zebra mussel and carp energy reserves and condition. Under in situ conditions, the same negative impact of Effluent 2 was observed for zebra mussels, while Effluent 1 had no apparent effect on exposed zebra mussels. Carp growth and condition, on the other hand, were significantly increased at the discharge sites of both effluents when compared to the reference site, probably due to differences in food availability. The results indicate that a combination of in situ and laboratory exposures can illustrate how ecological processes influence bioassay studies. The incorporation of indirect, ecological effects, like changes in food availability, provides considerable benefit in understanding and predicting effects of effluents on selected species under realistic exposure conditions.     

改性TiO_2/浮石光催化去除二级出水中有机物

为了实现城市污水厂二级出水的回用,将La3＋、Fe3＋共掺杂TiO2/浮石光催化用于二级出水中有机物的去除。在优化工艺条件下,该方法对TOC的去除率为49.0%,对UV254的去除率为76.5%;出水BDOC/DOC值大幅度提高,由最初的0.21提高到0.56,增加了出水的可生化性;二级出水中存在着影响光催化去除有机物的因素,其中阴离子对有机物的去除有一定的抑制作用;光催化反应在通过O3强化后对有机物的去除率得到提高,TOC的去除率达到75.0%,光催化和O3氧化对有机物的去除具有协同效应;随着光催化反应次数的增加,催化剂活性有下降趋势,使用10次后TOC去除率下降到第一次使用时的16.7%,再生能够使催化活性恢复到使用前的95%,催化剂在使用15次以内稳定性较好。     

Effects of wastewater disinfection on waterborne bacteria and viruses.

Wastewater disinfection is practiced with the goal of reducing risks of human exposure to pathogenic microorganisms. In most circumstances, the efficacy of a wastewater disinfection process is regulated and monitored based on measurements of the responses of indicator bacteria. However, inactivation of indicator bacteria does not guarantee an acceptable degree of inactivation among other waterborne microorganisms (e.g., microbial pathogens). Undisinfected effluent samples from several municipal wastewater treatment facilities were collected for analysis. Facilities were selected to provide a broad spectrum of effluent quality, particularly as related to nitrogenous compounds. Samples were subjected to bench-scale chlorination and dechlorination and UV irradiation under conditions that allowed compliance with relevant discharge regulations and such that disinfectant exposures could be accurately quantified. Disinfected samples were subjected to a battery of assays to assess the immediate and long-term effects of wastewater disinfection on waterborne bacteria and viruses. In general, (viable) bacterial populations showed an immediate decline as a result of disinfectant exposure; however, incubation of disinfected samples under conditions that were designed to mimic the conditions in a receiving stream resulted in substantial recovery of the total bacterial community. The bacterial groups that are commonly used as indicators do not provide an accurate representation of the response of the bacterial community to disinfectant exposure and subsequent recovery in the environment. UV irradiation and chlorination/dechlorination both accomplished measurable inactivation of indigenous phage; however, the extent of inactivation was fairly modest under the conditions of disinfection used in this study. UV irradiation was consistently more effective as a virucide than chlorination/dechlorination under the conditions of application, based on measurements of virus (phage) diversity and concentration. Taken together, and when considered in conjunction with previously published research, the results of these experiments illustrate several important limitations of common disinfection processes as applied in the treatment of municipal wastewaters. In general, it is not clear that conventional disinfection processes, as commonly implemented, are effective for control of the risks of disease transmission, particularly those associated with viral pathogens. Microbial quality in receiving streams may not be substantially improved by the application of these disinfection processes; under some circumstances, an argument can be made that disinfection may actually yield a decrease in effluent and receiving water quality. Decisions regarding the need for effluent disinfection must account for site-specific characteristics, but it is not clear that disinfection of municipal wastewater effluents is necessary or beneficial for all facilities. When direct human contact or ingestion of municipal wastewater effluents is likely, disinfection may be necessary. Under these circumstances, UV irradiation appears to be superior to chlorination in terms of microbial quality and chemistry and toxicology. This advantage is particularly evident in effluents that contain appreciable quantities of ammonia-nitrogen or organic nitrogen.     

Biological denitrification in drinking water treatment using the seaweed Gracilaria verrucosa as carbon source and biofilm carrier.

Chemical and microbiological aspects were investigated with regard to biological denitrification of drinking water using the seaweed Gracilaria verrucosa as the carbon and energy substrate and as physical support for the microbial flora in semibatch, fixed-bed reactors. Complete removal of nitrate (100 mg/L) was readily achieved without accumulation of nitrite. Microbiological analysis indicated that the effluent of the reactor contained high numbers of bacteria (>10(6)/mL total count). Among the 44 bacterial strains isolated directly from the samples or isolated after enrichment at 37 degrees C, 25 different fatty acid profiles were found, indicating a complex microflora, including potential pathogens.     

Removal of arsenic from groundwater by granular titanium dioxide adsorbent

A novel granular titanium dioxide (TiO2) was evaluated for the removal of arsenic from groundwater. Laboratory experiments were carried out to investigate the adsorption capacity of the adsorbent and the effect of anions on arsenic removal. Batch experimental results showed that more arsenate [As(V)] was adsorbed on TiO2 than arsenite [As(III)] in US groundwater at pH 7.0. The adsorption capacities for As(V) and As(III) were 41.4 and 32.4 mgg(-1) TiO2, respectively. However, the adsorbent had a similar adsorption capacity for As(V) and As(III) (approximately 40 mgg(-1)) when simulated Bangladesh groundwater was used. Silica (20 mgl(-1)) and phosphate (5.8 mgl(-1)) had no obvious effect on the removal of As(V) and As(III) by TiO2 at neutral pH. Point-of-entry (POE) filters containing 3 l of the granular adsorbent were tested for the removal of arsenic from groundwater in central New Jersey, USA. Groundwater was continuously passed through the filters at an empty bed contact time (EBCT) of 3 min. Approximately 45,000 bed volumes of groundwater containing an average of 39 microgl(-1) of As(V) was treated by the POE filter before the effluent arsenic concentration increased to 10 microgl(-1). The total treated water volumes per weight of adsorbent were about 60,000 l per 1 kg of adsorbent. The field filtration results demonstrated that the granular TiO2 adsorbent was very effective for the removal of arsenic in groundwater.     

BOD5 measurements of water presenting inhibitory Cu2+. Implications in using of BOD to evaluate biodegradability of industrial wastewaters

In industrial effluents, the presence of an infinite number of possible mixtures of substances and the high variability of chemical conditions ask for an evaluation of biodegradability by a global and simple method. Biological oxygen demand after five days (BOD5) using synthetic wastewater was studied by two different ways: dilution and manometric methods. It can therefore be established that BOD5 obtained by adding manufactured inocula to the synthetic medium (effluent containing known and easily biodegradable substances) is close to the values obtained with inocula taken from the treated effluent of an urban and a rural purification plant. It was found that BOD5 measurement of effluents presenting factors affecting biodegradation, similar of those found in industrial effluents, is very questionable. The BOD is in this case influenced by the synergic and antagonist interactions between numerous and variable parameters like as pH, nature and concentration of inoculum, concentration of nutriments, amount and nature of assimilable substances, presence of toxicants, and presence of nitrification inhibitors, which are typical of real industrial wastewaters.     

Combined use of molecular biology taxonomy, Raman spectrometry, and ESEM imaging to study natural biofilms grown on filter materials at waterworks

DNA-based population analysis was applied in combination with Raman spectrometry and Environmental Scanning Electron Microscopy for the characterisation of natural biofilms from sand and activated carbon filters operated for a long term at a municipal waterworks. Whereas the molecular biology polymerase chain reaction combined with denaturing gradient gel electrophoresis approach provides a deeper insight into the bacterial biofilm diversities, Raman spectrometry analyses the chemical composition of the extracellular polymer substances (EPS), microorganisms embedded in EPS as well as other substances inside biofilm (inorganic compounds and humic substances). Microscopy images the spatial distribution of biofilms on the two different filter materials. In addition, bacterial bulk water populations were compared with biofilm consortia using the molecular fingerprint technique mentioned.Population analysis demonstrated the presence of more diverse bacterial species embedded in a matrix of EPS (polysaccharides, peptides, and nucleic acids) on the sand filter materials. In contrast to this, activated carbon granules were colonised by reduced numbers of bacterial species in biofilms. Besides α-, β-, and γ-Proteobacteria, a noticeable specific colonisation with Actinobacteria was found on activated carbon particles. Here, the reduced biofilm formation came along with a decreased EPS synthesis. The taxonomy profiles of the different biofilms revealed up to 60% similarity on the same filter materials and 32% similarity of different materials. Similarity of adherent communities from filter materials and bulk water populations from the filter effluent varied between 36% and 58% in sand filters and 6–40% in granular activated carbon filters.The biofilm investigation protocols are most crucial to subsequent acquisition of knowledge on biofilm dynamics and bacterial contributions to transformation or adsorption processes in waterworks facilities.     

Occurrence of estrogenic effects in sewage and industrial wastewaters in Beijing, China

Estrogenic potencies of the effluents or water samples from wastewater treatment plants (WWTPs), industries and hospitals and some receiving rivers in Beijing city were estimated by using a human estrogen receptor recombinant yeast assay. Estrogenic activity of industrial wastewaters was found to range from 0.1 to 13.3 ng EEQ/L and decreased to the range of 0.03-1.6 ng EEQ/L after treatment. Estrogenic activity in WWTP influent ranged from 0.3 to 1.7 ng EEQ/L and decreased to the range of 0.05-0.5 ng EEQ/L after treatment. In the receiving river waters, the estrogenic effect range was 0.1-4.7 ng EEQ/L. These data suggest that treated industrial effluents and WWTP effluents of concern are not the only source of estrogenic pollution in surface waters in Beijing city. EEQ levels in Beijing river water are likely attributable to untreated municipal and industrial wastewaters discharged directly into the river.     

Lysimeter Test of Coke Plant Effluent Disposal to Land in India

ABSTRACT

From the Indian national point of view, the importance of coal carbonizing industries is great and growing. These industries produce huge quantities of highly polluted effluents and discharge them into rivers without proper treatment. A large coke plant of Bharat Coking Coal Ltd. has been surveyed, and the impact of its effluent on surface water quality is discussed. Approximately 175-200 m³ of effluents are discharged from the plant every day. Land application has been considered as a low-cost means of disposal of coke oven effluents. Column lysimeters were prepared by collecting soil from a nearby agricultural field, putting it layerwise into a column, and compacting it carefully to simulate the original in situ conditions. Raw effluents, diluted effluent, and water (as a blank) were applied to the three lysimeters twice a week with a 5 cm flooding. Upon application of diluted effluent (1:1) into lysimeter No. 2, the leachate collected at 190 cm depth was within the tolerance limit of drinking water standard (IS 10,500). The impact of raw and diluted effluent on groundwater quality and soil are discussed. The renovation efficiency of living filter (lysimeter No. 2) was 99.37% for oil and grease, 86.92% for COD, and 53.22% for TDS, and it is estimated that 2.73 hectares of land can be irrigated with the effluents of the coke plant without deteriorating groundwater and soil quality.     

Characterization and modeling of nutrient-deficient tomato-processing wastewater treatment using an anaerobic/aerobic system

Tomato-processing wastewaters are typical of slowly biodegradable high strength wastewaters generated from the food canning industry. Three different samples of influent and three samples of anaerobic effluents corresponding to the three influents collected from an on-site pilot-scale anaerobic/aerobic system were characterized using respirometric methods. Respirometric studies demonstrated that the pretreatment in the anaerobic reactor of the pilot-scale system increased the readily biodegradable fraction from an average of 40% of the SCOD in the influent to 50% of the SCOD in the anaerobic effluent, improved kinetics from an average micro(max) of 1.5d(-1) in the influent to 3.5d(-1) in the anaerobic effluent, and eliminated nutrient deficiency. Furthermore, the system was calibrated and simulated by application of wastewater characterization and biokinetic data derived form respirometric tests of influent and anaerobic effluent in Activated Sludge Model no.1 (ASM1).     

丙烯腈废水及几种处理工艺出水的毒性

分别利用小麦、发光菌毒性测试技术研究了模拟丙烯腈废水以及几种处理工艺出水对小麦芽伸长、根伸长、发芽率和发光菌发光度的毒性效应差异。结果表明,丙烯腈对小麦芽伸长的毒性影响最大;各类物质对小麦根伸长和发芽率并未造成毒性影响;其他物质对发光菌发光度的毒性最大。模拟废水对小麦芽伸长、根伸长、发芽率和发光菌发光度的毒性效应分别为:部分相加、部分相加、协同和拮抗作用。几种处理工艺出水对上述指标的毒性影响顺序依次是:模拟废水加成出水活性炭吸附出水Fenton法出水;Fenton法出水模拟废水加成出水活性炭吸附出水;Fenton法出水活性炭吸附出水模拟废水加成出水;活性炭吸附出水加成出水Fenton法出水模拟废水。比较几种处理工艺出水的毒性发现,几乎每种废水的毒性都有所降低,这说明几种处理工艺能有效降低模拟废水的毒性,具有深刻的实际指导意义。     

曝气生物活性炭滤池深度处理高浓度氨氮原水

实验研究曝气生物活性炭滤池对于高浓度氨氮原水的处理效果以及工艺运行稳定情况。以某自来水厂常规工艺沉淀池出水预加硫酸铵作为研究对象,原水氨氮平均浓度3.67 mg/L,实验条件:温度31.2℃,pH 7.13,滤速8~12 m/h,气水比0.5和1。采用3种不同工况条件进行实验,确定滤速10 m/h和气水比0.5的为最佳运行工况。在此工况下曝气生物活性炭滤池对于氨氮和COD Mn的平均去除率分别达到87.5%和19.2%,亚硝酸盐积累率为0.9%;出水氨氮浓度达到生活饮用水卫生标准GB5749-2006。同时炭滤池的出水浊度相比进水略微上升。     

Survey of perfluorinated alkyl acids in Finnish effluents, storm water, landfill leachate and sludge

The objective of the Control of Hazardous Substances in the Baltic Sea (COHIBA) project is to support the implementation of the HELCOM Baltic Sea Action Plan regarding hazardous substances by developing joint actions to achieve the goal of “a Baltic Sea with life undisturbed by hazardous substances”. One aim in the project was to identify the most important sources of 11 hazardous substances of special concern in the Baltic Sea. Among them are perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). In this study, four perfluorinated alkyl acids (PFAAs) were studied: PFOA, PFOS, perfluorohexanoic acid (PFHxA) and perfluorodecanoic acid (PFDA). The occurrence of PFAAs in municipal and industrial wastewater treatment plant effluents (MWWTP1-3, IWWTP1), target industry effluent, storm water, landfill leachate and sludge was studied. Effluents were analysed six times and storm water, leachate and sludge were analysed twice, once in the warm season and once in the cold, during a 1-year sampling campaign. PFOS prevailed in two municipal effluents (MWWTP1 and 3) and industrial effluent (IWWTP1; 7.8–14, 8.0–640 and 320–1,300 ng/l, respectively). However, in one municipal effluent (MWWTP2) PFOA was, in a majority of sampling occasions, the predominant PFAA (9–15 ng/l) followed by PFOS (3.8–20 ng/l). The highest PFAA loads of the municipal effluents were found in the MWWTP3 receiving the biggest portion of industrial wastewater. In storm water the highest concentration was found for PFHxA (17 ng/l). The highest concentration of PFOS and PFOA were 9.9 and 5.1 ng/l, respectively. PFOS, PFOA and PFHxA were detected in every effluent, storm water and landfill leachate sample, whereas PFDA was detected in most of the samples (77 %). In the target industry, PFOS concentrations varied between 1,400 and 18,000 μg/l. In addition, on one sampling occasion PFOA and PFHxA were found (0.027 and 0.009 μg/l, respectively). For effluents, PFAA mass flows into the Baltic Sea were calculated. For municipal wastewater treatment plants average mass flows per day varied for PFOS between 1,073 and 38,880 mg/day, for PFOA 960 and 2,700 mg/day, for PFHxA 408 and 1,269 mg/day and for PFDA 84 and 270 mg/day. In IWWTP mass flows for PFOS, PFOA, PFHxA and PFDA were 495 mg/d, 28 mg/d, 23 mg/d and 0.6 mg/g, respectively.     

Studies on thio-substituted polyurethane foam (T-PUF) as a new efficient separation medium for the removal of inorganic/organic mercury from industrial effluents and solid wastes

Novel thio-substituted flexible polyurethane foam (T-PUF) was synthesised by addition polymerisation of mercaptan with the precursors of an open-cell polyurethane foam, which can be used as a highly selective sorbent for inorganic and organic mercury from complex matrices. The percentage extraction of inorganic mercury was studied at different flow-rates, over a wide pH range at different concentrations ranging from 1 ppm, to 100 ppm. The break-through capacity and total capacity of unmodified and thio-foams were determined for inorganic and organic mercurials. The absorption efficiency of thio-foam was far superior to other sorbent media, such as activated carbon, polymeric ion-exchange resins and reagent-loaded polyurethane foams. It was observed that even at the 1000 ppm level, divalent ions like Cu, Mg, Ca, Zn do not appreciably influence the per cent extraction of inorganic mercury at the 10 ppm level. These matrix levels are the most concentrated ones which are likely to occur, both in local sewage and effluent waters. Further, the efficiency of this foam was sufficiently high at 10-100 ppm levels of Hg, even from 5-10 litres of effluent volumes using 50 g of thio-foam packed into different columns in series. Thio-foams were found to possess excellent abilities to remove and recover mercury even at low levels from industrial effluents and brine mud of chlor-alkali industry after pre-acid extraction. This makes it a highly efficient sorbent for possible application in effluent treatment. Model schemes for the removal and recovery of mercury from industrial effluents and municipal sewage (100-1000 litre) by a dynamic method are proposed and the costs incurred in a full-scale application method are indicated to show that the use of thio-foam could be commercially attractive.     

Toxicity to Microtox, micro-algae and duckweed of effluents from the Bai Bang paper company (BAPACO), a Vietnamese bleached kraft pulp and paper mill

Toxicity of the combined effluent as well as effluents from different production units of BAPACO, a Vietnamese bleached kraft integrated pulp and paper mill, was studied using three ecotoxicological tests: Microtox, the micro-alga, Selenastrum capricornutum, and the duckweed, Lemna aequinoctialis. Physico-chemical characteristics of the effluents were also analyzed. Due to unstable operating conditions of the mill, a number of samples taken at different monitoring periods from each effluent were tested, in order to get statistically reliable ranges and averages of toxicity characteristics. For the mill combined effluent, it was found that the micro-algae were the most sensitive followed by Microtox bacteria, while duckweed was not sensitive. Microtox tests showed that the bleaching filtrate from the chlorination stage (C-stage) was the most toxic among all effluents in the mill. The combined effluent from the bleaching plant contributed the largest TEF (Toxicity Emission Factor) to the toxicity balance of the whole BAPACO combined effluent. A less-than-additive mode of toxicity was obtained. In spite of high pollution loads, e.g. BOD, COD, SS, to the Red River, the toxicity of the effluent was considered to be low. However, during periods of low river water sublethal toxic effects on the biota may be expected.     

Sources of adsorbable organic halogens (AOX) in sludge of Gaza

Average concentrations of adsorbable organic halogens (AOX) in sludge from the Gaza Strip reached 600 mg kg(-1) which currently represents a major limiting factor for sludge application in agriculture. This study aims to identify the main sources of AOX in Gaza where the area is small with limited industrial activities. The results showed that the AOX in effluent sludge is formed mainly inside the treatment plant. Although the plant receives AOX wastewater of only 85 microg l(-1), this value increased five fold inside the plant to an average of 400 microg l(-1) in the effluent wastewater. On the other hand, the sludge from the first sedimentation pond showed an AOX concentration of 213 mg kg(-1) and increased in the final sedimentation pond to 500 mg kg(-1). The AOX concentration in three month old sludge was 130 mg kg(-1). The textile and detergent industries are the major AOX producing industries in Gaza, with an average AOX of 40,000 microg l(-1) in their effluent wastewater. These values do not represent a significant AOX pollution load to the treatment plant because these industries are very limited and their effluents are diluted before entering the municipal treatment plant. Industrial activity decreased in 2006 to less than 70% of the previous four years. Consequently, the AOX in the industrial effluent decreased from 150,000 to 40,000 microg l(-1) over the same time period. Sludge from these industries showed 1300 mg kg(-1) AOX for the past four years and only 400 mg kg(-1) in 2006. Moreover, the AOX in the influent wastewater discharged to the treatment plant decreased from 320 to 85 microg l(-1) for the same period. This study revealed that the major AOX is formed inside the treatment plant and especially in the anaerobic facilities. There was no correlation between the AOX concentrations in the sludge and the wastewater at the same location. Moreover, there was no correlation between the AOX in sludge/wastewater and dissolved oxygen, pH and chloride in that treatment plant.     

Evaporation behaviour of different organic effluents from open surfaces

Production of large quantities of effluents from different industrial units and the problems of their disposal necessitated this evaporation study. The evaporation of water, sewage water, oil refinery effluent, papermill effluent and liquor distillery effluent was observed in glass beakers when placed (i) in an oven at 60 degrees C and (ii) in screen house for 30 days, by periodically weighing of the beakers. In other experiments, the effect of increasing the frequency of stirring on increasing the evaporation efficiency of the liquor distillery effluent (ELD) was examined in detail. All of the organic effluents except ELD had similar evaporation behaviours as water, but formation of a self-forming film caused the evaporation of ELD to be considerably lower. Resistance to evaporation caused by this film was found to be a decreasing function of the frequency of stirring. This study has a bearing on improving the efficiency of evaporation lagoons, and three stirrings in a day with a manually drawn stirrer in a full-scale lagoon are proposed as a practical and economically viable technique to save 44% of lagoon land in arid and semi-arid regions of the world.     

Effects of an industrial effluent on plant colonization and on the germination and post-germinative growth of seeds of terrestrial and aquatic plant species

Major oil sands industrial companies are located in the Athabasca Oil Sands Deposit in northeastern Alberta, Canada. During the process used to extract light crude oil (via hot water digestion and flotation), gypsum is usually added to produce consolidated tails (CT) and CT release water. The vast volumes of process-treated waters (effluent) are held within large dyked tailings ponds. Toward testing viable options for reclamation, various hummock-wetlands systems have been constructed; in addition, natural wetlands (inhabited by obligate wetland plant species) have become established as a result of seeping of the effluents held within the large dyked ponds. Vegetation surveys conducted on and around the industrial site revealed that the constructed wetlands associated with the dyke drainage (effluent treated with phosphorous) and consolidated tails (CT; effluent treated with gypsum) had low biodiversity and were not invaded by many aquatic plants. Although the natural wetland was also not invaded by many aquatic species, it was found to be as diverse as the reference wetlands (i.e. off-site wetlands not exposed to the effluents). Exposure to oil sands effluents had an inhibitory effect on the germination (percent and/or rate) of several plant species (tomato, clover, wheat, rye, pea, reed canary grass, loblolly pine); clover and tomato seed germination were most affected. Two treatments in particular (effluents from the natural on-site wetland and the CT constructed wetland), delayed germination, and also led to reduced fresh weight of seedlings of tomato, wheat, clover and loblolly pine. The osmolarities of the effluents associated with the natural on-site wetland and CT constructed wetland were 712 and 728 mOs/kg, respectively; substituting these effluents with solutions of polyethylene glycol of the same osmotic potentials had a greater inhibitory effect on germination rate. The negative effects of the effluents on seed germination may account for the paucity of aquatic species that invaded the oil sands impacted wetlands. This factor will also be critical in determining the long-term feasibility of hummock-wetland systems.