Batch adsorption of organic pollutants from oxidation pond effluents using fly ashes

The batch shaking adsorption study was conducted to determine the potential of fly and volcanic ashes in removing organic pollutants from oxidation pond effluents. Factors affecting organic pollutant removals, such as concentrations and sizes of fly and volcanic ashes, initial pond effluent organic concentrations, washed and unwashed conditions of fly and volcanic ashes, were investigated. The TOC (total organic carbon) removal efficiency varied from 30 to 58 percent. The organic removal efficiency increased with increasing ash concentrations, with decreasing initial pond effluent organic concentrations and with decreasing sizes of ashes.     

Improved electroflotation for the removal of suspended solids from algal pond effluents

Experiments with a patented modification of an electroflotation cell showed that the power requirements for the treatment of pond effluents were less than for other electroflotation methods. The relationship between current densities and removal efficiencies of algae in suspension was found in laboratory and pilot-scale experiments. It was found that simultaneous flocculation-electroflotation gives better results than consecutive operation. The results obtained with electroflotation even with low current densities were almost equal to dissolved air flotation. It is believed that better adherence of electrolytically produced gases to the floc is responsible for the superiority of electroflotation.     

Fenton and photo-Fenton oxidation of textile effluents

The simultaneous use of Fenton reagent and irradiation for the treatment of textile wastewaters generated during a hydrogen peroxide bleaching process is investigated. The experimental conditions tested during this study provide the simultaneous occurrence of Fenton, Fenton-like and photo-Fenton reactions. The batch experimental results are assessed in terms of total organic carbon reduction. Identification of some of the chemical constituents of the effluent was performed by means of GC-MS. Other pollution related features of the initial effluent-like COD and color were also measured. The main parameters that govern the complex reactive system, i.e., light intensity, temperature, pH, Fe(II) and H2O2 initial concentrations have been studied. Concentrations of Fe(II) between 0 and 400 ppm, and H2O2 between 0 and 10,000 ppm were used. Temperatures above 25 degrees C and up to 70 degrees C show a beneficial effect on organic load reduction. A set of experiments was conducted under different light sources with the aim to ensure the efficiency of using solar light irradiation. The combination of Fenton, Fenton-like and photon-Fenton reactions has been proved to be highly effective for the treatment of such a type of wastewaters, and several advantages for the technique application arise from the study.     

Formation of nitrosodimethylamine (NDMA) during chlorine disinfection of wastewater effluents prior to use in irrigation systems

The probable human carcinogen nitrosodimethylamine (NDMA) is produced when wastewater effluent is disinfected with chlorine. In systems where wastewater effluent is used for landscape or crop irrigation, relatively high chlorine doses (i.e., up to 2,000,mg-min/L) are often used to ensure adequate disinfection and to minimize biofouling in the irrigation system. To assess the formation of NDMA in such systems, samples were collected from several locations in full-scale wastewater treatment systems and their associated irrigation systems. Up to 460 ng/L of NDMA was produced in full-scale systems in which chloramines were formed when wastewater effluent was disinfected with chlorine in the presence of ammonia. Less than 20 ng/L of NDMA was produced in systems that used free chlorine (i.e., HOCl/OCl(-)) for disinfection in the absence of ammonia. The production of NDMA in ammonia-containing systems was correlated with the concentration of NDMA precursors in the wastewater effluent and the overall dose of chlorine applied. Much of the NDMA formation occurred in chlorine contact basins or in storage basins where water that contained chloramines was held after disinfection. When landscape or crop irrigation is practiced with ammonia-containing wastewater effluent, NDMA production can be controlled by use of lower chlorine doses or by application of alternative disinfectants.     

Effect of industrial wastes on oxidation pond performance

Cadmium, copper, nickel, zinc and hexavalent chromium ions were tested in a benchbioassay experiment for toxicity limits and possible application to experimental oxidation ponds.     

Catalyzed UV oxidation of organic pollutants in biologically treated wastewater effluents

A batch reactor was used to evaluate the efficiency of advanced oxidation process of the organic pollutants in biologically treated wastewater effluents with UV/H2O2. A 450-W high-pressure mercury vapor lamp was used as the light source. During the degradation process, the concentration of the dissolved organic compounds could be increased by more than twofold due to the decomposition of microorganisms. This increase of the dissolved organic compounds was eliminated if the water was filtered before the photodegradation experiments. It is observed that the UV alone could play a role for the oxidation of the organic pollutants; however, the addition of a small amount of hydrogen peroxide promotes the degradation efficiency of organic compounds in wastewater. The best oxidation efficiency was obtained when the water samples were under acidic conditions (pH 5), and the rate of degradation was not enhanced with the increasing H2O2 dosages. The optimum H2O2 dose was between 0.01% and 0.1% for the oxidation processes in this study. The presence of the carbonate/bicarbonate ions in water inhibits the degradation of the organic compounds.     

Material balances of organics and nutrients in an oxidation pond

A series of experiments concerning a tertiary oxidation pond was performed from 10 January to 12 November 1979, using a model oxidation pond of 21 m² in capacity. The concentrations of organics and nutrients in influent and pond water were measured so as to consider the conversion of water quality in a tertiary oxidation pond. The sedimentation rates were measured weekly, and the final sediments were analyzed at the end of experiments, so that the material balances in respect to carbon, nitrogen and phosphorus were calculated and the various transition reactions were evaluated quantitatively. The result of the material balances showed that there were three main reactions in pond: the assimilation to algae; the sedimentation of suspended substance; and the decomposition of sediments. The regeneration rates of nutrients from sediments were so active that the removal of nutrients by algal solidification were not effective. Consequently, the overall removal efficiency of nutrients was 45% in total nitrogen and 43% in total phosphorus by a tertiary oxidation pond with 16 days detention time.     

Nanofiltration removal of chlorinated organic compounds from alkaline bleaching effluents in a pulp and paper plant

Three commercial nanofiltration membranes were used for the removal of chlorinated organic compounds from the first alkaline extraction effluent originated from a kraft mill, using eucalyptus wood as raw material. The assays were carried out at the following operating conditions: pressure = 20 bar, TEMPERATURE = 20°C and circulation VELOCITY = 2 m/s. The results show the nanofiltration feasibility. For the three membranes the rejection factors of chlorinated organic compounds are greater than 95% and two of them present permeate fluxes of approx. 42 kg/hm². Several reference solutes with a wide range of molecular weights and functional groups were also permeated. Their results compared with those of mill effluent allow us to conclude that the effluent tannic compounds are not in a fouling form and that the majority of the organochlorinated matter has a molecular weight greater than 500 Da.     

Preliminary feasibility study for the use of an adsorption/bio-regeneration system for molinate removal from effluents

This work studies the feasibility of the use of a combined physical-biological remediation procedure for treatment of effluents contaminated with molinate, where the herbicide is removed through adsorption and biodegraded in a subsequent stage, with the regeneration of the adsorbent. In order to select the most adequate absorbent for molinate, different materials were tested, namely pine bark, activated carbon and resin Amberlite XAD-4. Activated carbon and resin Amberlite XAD-4 were the most efficient on the removal of molinate from solutions, although the activated carbon used proved not to be bio-regenerable. It was also observed that factors such as temperature, pH, and conductivity did not affect significantly molinate adsorption onto resin Amberlite XAD-4. Resin Amberlite XAD-4 was successfully bio-regenerated, being observed that biodegradation was mainly dependent on spontaneous desorption of the molinate. After bio-regeneration, the resin could be re-utilised as adsorbent.     

Operation of a deep, well-mixed, high-rate photosynthetic oxidation pond

The maximum depth for the stable operation of a photosynthetic high-rate oxidation pond was found to be 90cm. At this depth, both the pH and the peak oxygen concentration were significantly lower than the values obtained in shallow high-rate oxidation ponds.     

Criteria for the control of radioactive effluents

The risks to the population from the U.S. nuclear energy industry are considered to be very small in comparison with other environmental risks. However, they are not zero and, on the assumption that radiation damage increases linearly with the accumulated dose, they can be expected on a statistical basis to result in a few deaths in the exposed population. Thus, the routine operation of these nuclear power plants may cause about 18 deaths/yr and the serious accidents, which may occur at a frequency of once every 50 yr, may add another 6 deaths/yr on the average. This is considered to be a small price to pay relative to the real but less‐well‐defined environmental risks from atmospheric pollution caused by fossil fuel power plants. Assuming the proper selection of a reactor site and all practicable precautions in the design and operation of a nuclear power reactor, adequate radiation protection for nearby populations can be assured by concentrating health physics attention on the critical radionuclides, critical pathways and critical segments of the population.     

Microbial reactions in facultative oxidation ponds—II. Biochemical activity of facultative oxidation pond sediments

Studies of biochemical reactions involved in the decomposition of organic matter in sediments of a facultative oxidations pond have shown that the reactions most sensitive to anaerobic conditions increased in activity with increasing pond depth. Other reactions less affected by anaerobic conditions showed little or no change. Use of these parameters in the examination of malfunctioning ponds is also indicated.     

Combined advanced oxidation and biodegradation of industrial effluents from the production of stilbene-based fluorescent whitening agents

Three different industrial wastewaters from the production of stilbene-based fluorescent whitening agents were investigated with regard to the applicability of advanced oxidation processes combined with biodegradation. Oxidation processes included the application of ozone, hydrogen peroxide, UV-radiation and Fenton's reagent (Fe(2+)/H(2)O(2)). Characterization of the combined chemical-biological treatment was done by sum parameters and HPLC analysis. In addition, toxicity was determined using the luminescence inhibition test. Results showed that processes producing OH-radicals without the need of UV-irradiation proved to be suited for the oxidation of all three wastewaters. H(2)O(2)/UV processes were ineffective due to the high inner filter effect of the effluents. Comparing the combined oxidative-biological process with biological treatment, the applied pre-oxidation steps did not always lead to a significant improvement of the biological degradation. In one case, an inverted treatment starting with biodegradation followed by oxidation turned out to be the preferable procedure. After oxidation with ozone or ozone combined with UV-irradiation, an increase in toxicity was partly observed indicating the formation of toxic intermediate products. In some cases samples had to be diluted before the biodegradation step to achieve a better biodegradability.     

Computational study of flow characteristics of acid mine drainage on the structure of oxidation pond

A computational flow analysis using the concept of the inflow age was conducted to evaluate the flow characteristics and retention time depending on the shape and number of inlets and outlets in an oxidation pond. The oxidation pond was rectangular in shape with a width‐to‐length ratio of 3, a depth of 3 m, an area of 500 m², and square‐shaped inlet and outlet. The flow rate of the mine drainage was set to 5 L/s. The computational flow analysis showed that the homogeneity and inflow exchange efficiency were the highest when the width‐to‐height ratio of the inlet and outlet was 0.5, while they were the lowest when it was 1.0. The number of inlets in the oxidation pond had a significant effect on the flow characteristics in the pond, whereas the number of outlets had no significant effect. The homogeneity and inflow exchange efficiency appeared to be the highest when the number of inlets was two.     

Investigation of errors associated with the use of cascade impactors

The magnitude of some errors associated with the use of cascade impactors for atmospheric aerosol sampling has been estimated by a number of experiments in the field. Three types of impactors namely the Andersen Ambient, the Battelle and the Lundgren have been compared. As impaction surfaces Whatman 41 cellulose filter and Fresh-Pack polyethylene were applied, with and without adhesive coating. The collection efficiencies were evaluated on the basis of concentration data obtained by INAA for 10 elements. It appears that for sampling times of at least 95 hours the wall-losses and the bounce-off effects in the Andersen are less influenced than in the Battelle by changing the impaction surface or by coating it with Apiezon. The Andersen yields very reproducible mass-size functions. This impactor is also very insensitive to its positioning upright or downwards or to the addition of a specially modified inlet. It was reassuring to note that the Andersen and Battelle impactor collect, within 10%, the same mass and yield very similar MMD values. With the Lundgren impactor slightly deviating results were obtained.     

对当前城市消防规划编制工作的研究

以当前城市消防规划编制工作的开展现状为切入点,着重阐述了当前城市消防规划编制中存在的问题,并结合实际工作经验,提出了相应的解决措施,以消除消防安全隐患,保证社会公众群体的生命财产安全。     

喷灌与滴灌相结合的灌溉模式设计探析

对管道灌溉、滴灌、喷灌等灌溉方式进行了介绍,着重探讨了灌溉模式的选择方法及要点,指出对于开荒地,选择喷灌和滴灌相结合的方式,既减少了出地管的数量,又方便耕作,具有较好的经济效益。     

Waste stabilization pond performance in Pakistan and its implications for wastewater use in agriculture

Faisalabad is one of the few cities in Pakistan that has a waste stabilization pond (WSP) system. Local farmers complained about the high salinity and low nutrient value of the final effluent from the WSP and preferred the use of untreated wastewater. A one-year study showed a strong increase in salinity from untreated wastewater to final effluent with a clear decline in nitrogen concentration, thereby confirming farmer perceptions. The performance of the WSP was poor and did not comply with World Health Organization (WHO) and Food and Agricultural Organization (FAO) guidelines for irrigation water. The poor performance of the WSP could be attributed to a combination of factors: poor design, the extreme climatic conditions and the large quantities of untreated wastewater which were used in agriculture. In countries such as Pakistan where the use of untreated wastewater has a long history, farmer perceptions should play a pivotal role in the selection of suitable wastewater treatment systems.