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Nitrogen and phosphorus removal in a methane fermentation plus activated sludge method type pig farm (M-III) with an intermittent aeration process (IAP) was evaluated in comparison with a continuous aeration process (CAP) based on the full-scale and bench-scale experiments. Operation conditions for the treatment system were the same except for the aeration program (in the CAP), a consecutive 24-hr aeration was used, whereas in the IAP, the aeration and non-aeration periods were alternated at intervals of 3:1 hr. BOD and TOC removal efficiencies with the intermittent aeration were as high as those with the continuous operation (92-98%). In the removal of nitrogen and phosphorus, large differences between IAP and CAP were observed. At an influent T-N/TOC ratio of 0.1, removal efficiencies for T-N in the bench-scale IAP was 70%, and for T-P was 22%, respectively. At an even higher influent T-N/TOC ratios of 0.3-1.0, the removal efficiencies for T-N were decreased to about 59-61%, whereas that for T-P were -0.3-13%. In a full-scale plant, removal efficiencies for T-N with IAP and CAP were 42% and -0.09%, respectively. The results of this study show the successful performance of a simple IAP for piggery wastewater: simultaneous, one-sludge denitrification with nitrification in single-activated sludge reactor in a pig farm.
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PMID:Removal of nitrogen and phosphorus from swine wastewater by intermittent aeration processes. 851 70

A process on crystallized precipitation of ammonium by adding magnesium salt and phosphate was carried out to improve C/N ratio in swine wastewater. After completion of crystallized precipitation of ammonium, an intermittent aeration process with aeration and nonaeration periods alternated at interval of 1:1 hr day-1 is used for the improved swine wastewater (T-N/BOD = 0.14: BOD = 8200 mg/liter and T-N = 1166 mg/liter). The results obtained from the experiment show that the removal ratios of T-N and NH4-N are 91% and 99%, respectively. T-P is not removed, while the removal ratio of PO4-P is 60% as 3% of CaCl2 liquid is added. The results also indicate that dilution with water is effective to improve the removal of phosphorus even if raw swine wastewater contains high concentrations of T-N, T-P, BOD, and TOC.
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PMID:Nitrogen and phosphorus removal for swine wastewater by ammonium crystallization and intermittent aeration process. 852 33

Domestic and wine-distillery wastewaters were treated by semi-batch and continuous pH sequential ozonations. The process involves a succession of acidic and alkaline wastewater pH conditions. The alkaline periods allow oxidation of organic matter by hydroxyl radical and produce carbonates that eventually would inhibit the oxidation. On the other hand, the acidic periods favour the development of direct ozone reactions and strip off carbonates as carbon dioxide from the wastewater. Experimental results of pH sequential ozonation showed degradation and removal rates of wastewater pollutants higher than those achieved at constant either acidic or basic pH. The most significant improvement of ozone efficiency and pollutants removal were obtained by controlling the number of cycles, pH and time of acidic and alkaline phases. Also, ozonated wastewaters showed high biodegradability as deduced from their BOD/COD ratios. The feasibility of treating domestic and wine-distillery wastewater by an integrated activated sludge (ASP)-pH sequential ozonation system was evaluated. Integrated ASP-ozonation at constant pH processes were also carried out for comparative purposes. In these combined experiments, pH sequential ozonation showed advantages compared to ozonation at constant pH in reducing global parameters such as COD, TOC and TKN, but ozonation at constant pH led to higher removal of polyphenols and UV254 absorbing compounds.
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PMID:pH sequential ozonation of domestic and wine-distillery wastewaters. 1123 88

Xenobiotic organics produced by modern industrial processes resist conventional biological wastewater treatment. Ozone pretreatment to improve biodegradation via partial oxidation is a potential solution for this recalcitrance. Ozone forms no additional sludge, removes colour and has two modes of action that can be utilised according to the wastewater constituents. The preozonation of a variety of wastewaters and model compounds is reviewed here. Of the industrial processes examined, the associated recalcitrant organic compounds were generally halogenated heterocyclic or nitrogenous aromatics, aliphatic polymers or polyaromatics. Initial optimisation of ozone dose ensured the occurrence of partial oxidation, where over 90% parent compound transformation was required to give best results in the subsequent biological process. Ozonation intermediate and end-products included ketones, aldehydes and organic acids that were more biodegradable than the parent compounds. Biodegradability improvement was assessed using TOC, COD, BOD, BOD/COD ratio and OUR. Actual process feasibility and performance was evaluated using various combined ozonation-biodegradation trials; textile dying and finishing effluent being one area of application. Kinetic studies of chemical and biological stages facilitated process optimisation and can assist scale-up. The main factors affecting ozonation performance were pH, the nature and concentration of oxidisable organics, ozone dose, competition between the target compound and biodegradable by-products, the presence of oxidant scavengers, and the efficiency of ozone mass transfer. The formation of toxic or recalcitrant by-products has been found to occur in some cases, necessitating knowledge of wastewater constituents and trials on a site-by-site basis.
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PMID:Partial oxidation by ozone to remove recalcitrance from wastewaters--a review. 1132 4

In this paper, the performance of a photoassisted electrolysis process, for the degradation of organic pollutants, is investigated. Results obtained in this work have shown that the thermally prepared anode of titanium, coated with 70TiO2/30RuO2, exhibits photoactivity and may be used for the treatment of effluents. A synthetic phenol aqueous solution and a real paper mill industry effluent were treated. Kinetic analysis showed a synergetic effect of electrolysis and photocatalysis and degradation rates are an order of magnitude greater than the sum of the results reached by using both processes individually. Using a 125 W mercury bulb and 20 mA cm-2, the phenol concentration decayed 85% in 90 min and 70% reduction of TOC was obtained. In the application of the treatment process for the degradation of the E1 bleach Kraft mill effluent, total phenols were practically eliminated in a short period of processing time, and color, usually resistant to biological treatment, was reduced to 10% from its initial value measured in terms of absorbance. Reductions of AOX, COD, and BOD by 25%, 30%, and 35%, respectively, were also observed.
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PMID:Photoassisted electrochemical degradation of organic pollutants on a DSA type oxide electrode: process test for a phenol synthetic solution and its application for the E1 bleach Kraft mill effluent. 1145 21

Our research aimed to evaluate intermittent soil infiltration of treated sewage for reuse in the north of Chile. Aerated lagoon effluent was infiltrated in columns packed with native soils (sandy-lime, lime-gravel and limey-sand). Columns were operated for more than a year under different cycles of filling and drying, depths and load pressures depending on soil characteristics. The efficiency of the system was determined through influent-effluent microbiological indicators level (faecal coliforms, E. coli, Salmonella spp, MS2 phage, and protozoan cysts), physicochemical characterisation (TOC, COD, BOD, nitrogen), and hydraulic flow measurement. Results showed: (a) high reduction of enteric bacteria (5-7 log10), some inactivation of phage (2-4 log10) and complete removal of intestinal cyst; (b) stable removal of organic matter (80-90% reduction of TOC, COD, BOD); and (c) partial ammonia reduction through adsorption and nitrification with denitrification mainly occurring in sandy soil. Preliminary data from pilot plant working in the field showed better results that those obtained in the laboratory especially removal of microbiological indicators. Microbiological quality of effluent met Class A regulations for agricultural reuse (WHO, 1989) and the system looks like an attractive alternative to cope with water shortage in the region.
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PMID:Water quality improvement of treated wastewater by intermittent soil percolation. 1146 52

Dyeing and finishing of textile yarns and fabrics are extremely important processes in terms of both quality and environmental concerns. Among the commercial textile dyes, particularly disperse dyestuffs are of environmental interest because of their widespread use, their potential for formation of toxic aromatic amines and their low removal rate during aerobic waste treatment as well as advanced chemical oxidation. Thus, in the present paper ferrous iron coagulation, ozonation and ferrous iron-catalyzed ozonation were employed at varying pH (3-13) and Fe(II)-ion doses (0.09-18mM) for the treatment of a simulated disperse dye-bath (average initial apparent color as absorbance at 566nm=815.4m(-1); COD(0)=3784mgl(-1); TOC(0)=670mgl(-1); BOD(5,0)=58mgl(-1)) that more closely resembled an actual dyehouse effluent than an aqueous disperse dye solution. Coagulation with 5000mgl(-1) FeSO4-7H2O (18mM Fe(2+)) at pH 11 removed up to 97% color and 54% COD, whereas oxidation via ozonation alone (applied ozone dose=2300mgl(-1)) was only effective at pH 3, resulting in 77% color and 11% COD removal. Fe(II)-ion-catalyzed ozonation (3.6mM Fe(2+) at pH 3; Fe(2+):O3 molar ratio 1:14) eliminated 95% color and 48% COD and appeared to be the most attractive option among the investigated chemical treatment methods as for its applicability at the natural acidic pH of the disperse dye-bath effluent and at relatively low Fe(2+)-ion doses as compared to ferrous sulfate coagulation. However, no TOC reduction was observable for ozonation and catalytic ozonation at the investigated reaction conditions (14gl(-1) O3 at pH 3). An average six-fold enhancement in the biodegradability parameter of the synthetic dye wastewater expressed in terms of the BOD(5)/COD ratio could be achieved by the investigated chemical treatment methods.
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PMID:Treatability of a simulated disperse dye-bath by ferrous iron coagulation, ozonation, and ferrous iron-catalyzed ozonation. 1148 26

Nearly 91% of organic pollutants in Hong Kong leachate could be effectively removed by the UASB (upflow anaerobic sludge blanket) process followed by the fenton coagulation. The COD (chemical oxygen demand) of leachate was lowered from an average of 5620 mg/L to 1910 mg/L after the UASB treatment at 37 degrees C, and was further lowered to 513 mg/L after fenton coagulation. The remaining refractory residues could be further removed by photochemical oxidation with the addition of H2O2. The BOD/COD ratio was greatly increased from 0.062 to 0.142, indicating the biodegradability of organic residues was improved. The photochemical oxidation for the fenton-coagulation supernatant was most effective at pH 3-4, with the addition of 800 mg/L of H2O2, and UV radiation time of 30 minutes. The final effluent contained only 148 mg/L of COD, 21 mg/L of BOD (biochemical oxygen demand) and 56 mg/L of TOC (total organic carbon).
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PMID:Photo-assisted fenton oxidation of refractory organics in UASB-pretreated leachate. 1221 91

A coarse pore filter can be applied inside the aeration tank to facilitate the separation of sludge from liquid instead of sedimentation. This filter has pores, which are irregular in shape, and the pore size is bigger than those of MF. The objectives of the study were to maintain as much as MLSS in the activated sludge process with coarse pore filter and to investigate the performance under high MLSS condition. Small-scale reactor results so far show good quality of effluent specially after starting the sludge bulking in the system in terms of SS, TOC, DOC and turbidity. The average carbon removal for 62 days operation of this system was about 94% (based on effluent DOC) and 87% (based on effluent TOC). The average sludge yield in this system is about 0.44 kg MLSS/kg TOC which is about 0.24 kg MLSS/kg BOD. This amount is less than those of conventional activated sludge and trickling filter.
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PMID:Performance of coarse pore filtration activated sludge system. 1252 35

The effect of ozonation on the biodegradability of 100-ppm aqueous solutions of 2,4-dichlorophenol has been investigated. BOD at 5, 10 and 21 days, BOD/COD and BOD/TOC ratios and the average oxidation state are presented. Biodegradability measured as BOD5/COD ratio was increased from 0 of the original solution to 0.25 at the moment of removing all the initial compound (corresponding to an ozone dose of 0.12 g L-1, 0.48 for BOD21/COD ratio). To test the effect of this pre-treatment, the biological oxidation of these pre-ozonated solutions was performed in two semi-continuous stirred tank reactors, one with non-acclimated sludge and one with acclimated-to-phenol sludge. The study showed that the TOC content of the pre-treated solution could be removed up to 68% by an aerobic biological treatment as well as co-digested with municipal wastewater (TOC removal up to 82%), with similar operating retention times to a municipal wastewater plant (12-24 h). Kinetic studies based on Monod model have also been carried out. Pseudo-first-order kinetic constants were found to be in the range of 0.5-0.8 L g TVSS-1 h-1.
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PMID:Contribution of the ozonation pre-treatment to the biodegradation of aqueous solutions of 2,4-dichlorophenol. 1450 3


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