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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

Inhibition of the organic matter consumption rate of a saline and rich proteic effluent by free ammonia was assessed in anaerobic filters at 37 degrees C. Inhibition of substrate (total organic carbon, TOC) consumption rate by ammonia was fitted by the Luong and noncompetitive models. Calculated kinetic parameters using the Luong model were maximum specific growth rate, micromax = 0.28 day(-1); average saturation constant, Ks = 568 mg TOC/L; Luong inhibition parameter, KNH3 = 1707mg ammonia-nitrogen (NH3-N)/L; and Luong exponent, gamma = 0.283 and the noncompetitive calculated parameters were umax= 0.26 day(-1), Ks = 703 mg TOC/L, and inhibition parameter, INH3 = 325 mg NH3-N/L. The Luong and noncompetitive models predicted 50% inhibition of the substrate consumption rate at ammonia concentrations of 147 and 325 mg NH3-N/L, respectively, suggesting biomass adaptation to the ammonia concentration (80 mg NH3-N/L as average) at which the anaerobic filters were previously operating. Ammonia formation by anaerobic digestion of fishing effluent would produce a maximum of 65.1 and 58.6% inhibition of the efficiency, predicted by the Luong and noncompetitive models, respectively. Ammonia influence on the digestion steps was determined by comparing fishing effluent with volatile fatty acids as substrates. The noncompetitive model predicted a 50% inhibition of methane production rate at ammonia concentrations of 196.6 and 188.6 mg NH3-N/L for fishing effluent and volatile fatty acids, respectively, suggesting that the methanogenic step is the one most affected by ammonia.
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PMID:Ammonia inhibition in the anaerobic treatment of fishery effluents. 1156 75

The two-stage anaerobic wastewater pre-treatment was modelled and controlled. The biological state of the reactors could be predicted using a fuzzy logic system and based upon this, proper control actions were taken automatically in order to avoid an overload. The system was designed to handle very strong fluctuations in the concentration of the substrate and the volumetric loading rate. Hydrogen concentration together with methane concentration, gas production rate. pH and the filling level of the acidification buffer tank were used as input variables for the fuzzy logic system. The manipulated variables were the flow rate from the acidification buffer tank into the methane reactor, the temperature and pH of both reactors, the circulation rate of the fixed bed reactor, back flow from the methane reactor into the acidification, and the control of the feed into the acidification buffer tank. The developed control system was successfully tested on a fully automated lab scale two-stage anaerobic digester. Different types of wastewater from food processing industries were successfully applied. Even a restart of feeding with very high COD concentrations (100 gl(-1) after several days of stand by was handled successfully. Effluent concentrations could be kept low without using TOC, COD or equivalent measurements.
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PMID:State detection and control of overloads in the anaerobic wastewater treatment using fuzzy logic. 1176 96

For several years, a 1 m3 fixed bed anaerobic digestion process has been operated for the treatment of distillery vinasses. This reactor has been fully instrumented with the following variables available on-line: pH, temperature, liquid and gas flow rates, gas composition (i.e., CH4, CO2 and H2), concentration of bicarbonate, chemical oxygen demand, total organic carbon, volatile fatty acids and partial and total alkalinity, these last four variables being measured twice by different techniques (i.e., using a TOC analyzer, a titrimetric sensor and an infrared spectrometer). The purpose of this paper is to compare the respective benefits of advanced instrumentation for the monitoring of wastewater treatment processes in general, and for anaerobic digestion in particular. It will also provide some statistical analysis of the time required to operate a fully instrumented wastewater treatment process. It is indeed well admitted in the literature that instrumentation is usually the main limitation step for using closed-loop control. However, it is our opinion that, in the near future, this situation will change. This point is discussed based on our four years practical experience.
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PMID:Evaluation of a four year experience with a fully instrumented anaerobic digestion process. 1193 72

A hybrid two-phase system, consisting of a solid waste reactor as the acidification reactor and a wastewater reactor, i.e. an upflow anaerobic sludge blanket (UASB) reactor, as the methanogenic reactor, for anaerobic digestion of food waste was investigated. After the pre-acidification stage, COD and total VFA removals in the methanogenic phase were in the ranges of 74-93% and 77-100%, respectively, while leachate COD and total VFA concentrations in the acidification phase decreased by 95% and 97-99%, respectively. Some 99% of the total CH4 generated was from the methanogenic phase with the CH4 content of 68-70%. About 77-79% of TOC, 57-60% of volatile solids and 79-80% of total COD were removed. The results of this laboratory-scale study show that the hybrid two-phase anaerobic batch reactor system is suitable for effective conversion of food waste into CH4 and CO2. The hybrid two-phase system can be further developed into an effective and efficient way to enhance waste stabilization in operating bioreactor landfills.
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PMID:A hybrid two-phase system for anaerobic digestion of food waste. 1220 Oct 98

A hybrid anaerobic solid-liquid (HASL) bioreactor was developed to enhance food waste conversion. The HASL bioreactor is a modified two-phase anaerobic digestion system with a solid waste reactor and a high-rate anaerobic wastewater reactor, which was a UASB reactor. In this study, the methanogenesis in the UASB reactor was investigated under a semi-continuous operation of the food waste digestion system. The HASL process, including 7 days of start-up and 23 days of semi-continuous operation followed by 6 days of batch operation, was commenced by loading 2.8 kg of shredded food waste. During the semi-continuous operation, 0.2 kg of the same waste was loaded daily. The leachate from acidification phase, i.e., solid waste reactor, remained acidic (pH 4.9-5.5) and high in total VFA (TVFA), 9,500-11,500 mg/L, and COD (8,000-11,800 mg/L) levels. In the methanogenesis phase, i.e., UASB reactor, effective TVFA and COD removals (88 +/- 5% and 85 +/- 7%, respectively) were obtained, while the methane content was 71%. At the end of operation, about 78% of VS added in the HASL bioreactor was removed, while TOC and total COD reductions were 78% and 79%, respectively. The results showed that the use of UASB reactor in the semi-continuous HASL system can enhance the methanogenesis process and increase the methane content in biogas production.
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PMID:Semi-continuous anaerobic digestion of food waste using a hybrid anaerobic solid-liquid bioreactor. 1453 36

Concentrations of ten DDTs (2,2-bis-(chlorophenyl)-1,1,1-trichloroethane) of which p,p'-DDA (2,2-bis(chlorophenyl)acetic acid), p,p'-DDM (bis(chlorophenyl)methane) and p,p'-DBP (dichlorobenzophenone) are often neglected, were measured in 25 water and 25 sedimentary samples from Bohai Bay and its adjacent Haihe Basin. The ratio of o,p'-DDX/p,p'-DDX in the upper reaches of Yongdingxin River ranged from 0.71 to 2.44, suggesting that the potential source of pollution would be the manufacturing or use of dicofol near this river. While DDA accounted for 52-93% of the SigmaDDT concentration in water, DDA was only detected in three sedimentary samples. And DDM was found to be an important degradation product of DDT in water following DDA. It should be noted that DBP (0.60-3.30 ng/g) is a major metabolite comparable with DDE (2,2-bis(chlorophenyl)-1,1-dichloroethylene, nondetectable-1.80 ng/g) and DDD (2,2-bis-(chlorophenyl)-1,1-dichloroethane, nondetectable-2.86 ng/g) in sediment in Bohai Bay. Finally, the SigmaDDT concentration in sedimentary sample from Bohai Bay was found to be dependent on the TOC (total organic carbon) value.
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PMID:Fate of DDT-related compounds in Bohai Bay and its adjacent Haihe Basin, North China. 1582 6

Controlled experiments were carried out in a mesoscale subsurface flow sand filter treating municipal wastewater from a single household. The system consisted of a 50 cm high vertical flow column (pre-filter) with unsaturated flow and a 3 m long horizontal subsurface flow unit (main filter) with saturated flow. Fluxes of nitrogen and carbon were analyzed in 4 different operating conditions (low and high loading, with and without the prefilter unit). Water samples were taken from the inlet, the outlet and within the sand filter at different depths and locations and analysed for water quality (Tot N, NO3-N, NH4-N, TOC, DOC, CODcr, BOD5, SS, pH, and EC) and dissolved gas content (N2O, CH4, and CO2). Emissions of N2O, CH4, and CO2 were measured with the closed-chamber technique adjacent to water quality sampling points. The results show that prefiltering in a vertical, unsaturated flow column changed the incoming ammonium to nitrate during low loading. During high loading part of the ammonium nitrified in the pre-filter was lost by denitrification. Within the horizontal main filter there were two pathways for the incoming nitrate: denitrification and dissimilatory nitrate reduction to ammonium (DNRA).
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PMID:Analysis of nitrogen removal processes in a subsurface flow carbonate sand filter treating municipal wastewater. 1592 Dec 89

High salinity is one of the most well known inhibitors and salt concentrations above 1% are reported as highly saline. Salt may be found in the main collectors of municipal sewer systems which carry the risk of seawater infiltration and where domestic wastewaters are treated with landfill leachates such cases in Istanbul. Discharging of leachates into sewerage would also result in additional ammonium loads in Municipal Treatment Plants (MTPs). In this study, synthetic wastewater was fed to a lab-scale Upflow Anaerobic Sludge Bed (UASB) reactor operated at a constant hydraulic retention time (HRT) of 1 day. The salt concentration was increased artificially whereas the ammonium concentration was fixed at 1000 mg/l throughout the study. Results indicated no significant inhibition up to 2% salinity + 1000 mg/l NH4 and TOC removals could reach up to 88%. Besides, effective total biogas productions having methane content of 84% could be achieved. It is obvious that anaerobic microorganisms (especially methanogens) could well adapt to high salinity ratios. No inhibition at high ammonium concentration might have been attributed to the fact that the pH in the system was not high enough for the formation of free ammonia. Investigation of the combined effect of high salinity and ammonium was carried on by increasing the salinity to 3% in the study. Results indicated that TOC removals decreased to around 56% and 3% salinity caused . a sharp decrease both in organic material removal and total biogas production. Thus the critical salinity level was determined as 3% for the methanogens in the mesophilic anaerobic digesters.
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PMID:Behavior of an Up-flow Anaerobic Sludge Bed (UASB) reactor at extreme salinity. 1611 24

Cherry stillage is a high strength organic wastewater arising from the manufacture of alcoholic products by distillation of fermented cherries. It is made up of biorefractory polyphenols in addition to readily biodegradable organic matter. An anaerobic sequencing batch reactor (AnSBR) was used to treat cherry stillage at influent COD ranging from 5 to 50 g/L. Different cycle times were selected to test biomass organic loading rates (OLR(B)), from 0.3 to 1.2 g COD/g VSS.d. COD and TOC efficiency removals higher than 80% were achieved at influent COD up to 28.5 g/L but minimum OLR(B) tested. However, as a result of the temporary inhibition of acetogens and methanogens, volatile fatty acids (VFA) noticeably accumulated and methane production came to a transient standstill when operating at influent COD higher than 10 g/L. At these conditions, the AnSBR showed signs of instability and could not operate efficiently at OLR(B) higher than 0.3 g COD/g VSS.d. A feasible explanation for this inhibition is the presence of toxic polyphenols in cherry stillage. Thus, an ozonation step prior to the AnSBR was observed to be useful, since more than 75% of polyphenols could be removed by ozone. The integrated process was shown to be a suitable treatment technology as the following advantages compared to the single AnSBR treatment were observed: greater polyphenols and color removals, higher COD and TOC removal rates thus enabling the process to effectively operate at higher OLR, higher degree of biomethanation, and good stability with less risk of acidification.
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PMID:Integration of ozonation and an anaerobic sequencing batch reactor (AnSBR) for the treatment of cherry stillage. 1620 60


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