Effects of coupling a UF membrane with a mesh screen and elevating temperature in the methanogenic digester of a two-phased anaerobic system.

This study was conducted to investigate coupling of UF with a mesh screen under thermophilic temperatures and compare the effectiveness of membrane filtration and temperature change in the methanogenic digester. A two-phased anaerobic digester coupled with an ultrafiltration (UF) membrane system was used for anaerobic sludge digestion. The overall average chemical oxygen demand (COD) removal efficiency achieved in the two-phased anaerobic digester coupled with the UF membrane system was 97.9 ± 0.8%. In the methanogenic digester, 10.5% improvement of methane production rate was obtained by the increased microbial population and metabolic activity due to coupling with a UF membrane and a mesh screen and elevating the temperature from mesophilic to thermophilic conditions. The average methane production per VS loading and unit volume (m3) was 477.14 ± 31.5 and 567.15 ± 43.3 mL CH4g-1 VS before and after elevating the temperature, respectively. The optimal operating pressure for the UF membrane system was less than 3 kgf cm-2, and the mesh screen saved 19.0% of the operating cost and 17.3% of energy consumption. As a result, the UF membrane system enhanced the digestion of sewage sludge, where the elevation of temperature improved the methane production rate in the thermophilic methanogenic digester.

Complete reduction of highly concentrated contaminants in piggery waste by a novel process scheme with an algal-bacterial symbiotic photobioreactor.

The complete reduction of highly concentrated contaminants in piggery waste was achieved with an innovative process scheme consecutively combining autothermal thermophilic aerobic digestion (ATAD), an expanded granular sludge bed (EGSB) and a microalgal-bacterial symbiotic vertical photobioreactor (VPBR), followed by biomass recycling for effluent polishing. Contaminants in piggery waste, such as high organic and inorganic matter, total nitrogen (TN), and total phosphorus (TP) contents, were successfully reduced in the newly implemented system. The concentrations of volatile solids (VS) and the chemical oxygen demand (COD) for organic matter in the feed were reduced by approximately 99.3% and 99.7%, respectively, in the innovative system. The overall reduction efficiencies in TN, ammoniacal nitrogen, and TP were 98.8, 98.4, and 93.5%, respectively, through ammonia gas emission, coagulated sludge disposal, and the algal-bacterial symbiotic polishing process. Fecal coliform density was decreased to <1.7 × 10(4) CFU g(-1) total solids. Biogas and CH4 in the EGSB were generated in the range of 0.36-0.79 and 0.18-0.44 L g(-1) [VS removed], respectively, and contained 245 ± 19 ppm (v/v) [H2S].

Control of membrane fouling with the addition of a nanoporous zeolite membrane fouling reducer to the submerged hollow fiber membrane bioreactor.

The membrane fouling control via the addition of nanoporous zeolite membrane fouling reducer (Z-MFR) to the submerged membrane bioreactor (MBR) was investigated. Using scanning electron microscopy/energy-dispersive X-ray (SEM/EDX) analysis techniques, the characteristics of fouling on a hollow fiber membrane surface were also analyzed. The addition of Z-MFR to the MBR led to the adsorption of foulants and the flocculation of mixed liquor suspended solids (MLSSs), which resulted in substantially enhancing the membrane filterability. The critical flux values obtained from the sewage mixed liquors of 3400 mg L(-1) at the effective dosage rate of 0.03 mg Z-MFR mg(-1) MLSS was 85 L m(-2) h(-1) (LMH), which was enhanced by 42%. The transmembrane pressure (TMP) variation under the operating conditions of 30 LMH with 3500 mg MLSS L(-1) showed that the addition of Z-MFR extended the time required to reach the critical flux of 0.32 bar by 2.6-fold longer than the control. Thus, due to the hybrid functions of adsorbing foulants and precipitating colloidal substances with the addition of Z-MFR, a decrease in the foulant amount and an improvement of sludge flocculation have been attained simultaneously. As a result, the membrane fouling control was achieved effectively with the addition of the Z-MFR.

Using porous ceramic media in the upflow packed-bed reactor (UPBR) system for nitrogen removal via autotrophic nitrification and denitrification.

In this study, the feasibility of an innovative upflow packed-bed reactor (UPBR) system using porous sulfur and lime ceramic media (CERAMED-L and CERAMED-SL) to remove nitrogen for wastewater treatment was evaluated. The specific lime dissolution rates for CERAMEDs in the UPBRs show an inverse proportion to pH and resulted in 2.32 g as CaCO(3) kg(-1) CERAMED-L d(-1) and 1.64 g as CaCO(3) kg(-1) CERAMED-SL d(-1) at a pH 6.7. The calculated specific nitrification rate resulted 1.73-2.29 kg NH(4)(+)-N m(-3) CERAMED-L d(-1), with a F/M ratio in the range 0.08-0.31 g NH(4)(+)-N g(-1) VS d(-1). The alkalinity shortage in the feed solution seemed to be overcome by supplying specific alkalinity of 3.88 kg as CaCO(3) m(-3) CERAMED-L d(-1) through the dissolution of lime from CERAMED-L. Autotrophic denitrification efficiencies were in the range of 83-96% during the test period, and the average specific denitrification rates of 0.97-1.92 kg NO(3)(-)N m(-3) CERAMED-SL d(-1) and 0.19-0.36 g NO(3)(-)-N g(-1) VS d(-1) were obtained.

Implementation of an excess sludge reduction step in an activated sludge process.

In this study, excess sewage sludge reduction resulting from the modification of an activated sludge process by incorporation of an excess sludge digesting reactor (ESDR) was examined. The ESDR was coupled to the sludge return line, and enhanced the solubilization of cell mass under thermophilic aerobic conditions. The decrease in the level of total suspended solids (TSS) observed in the reference ESDR (without thermophilic microbial inoculation) was 13.76% whereas a TSS decrease of 32.09% was achieved by the test ESDR (with thermophiles), thus showing microbial enhancement of solubilization of 18.33% over a test period of 48 h. The average excess sludge solubilization ratios (beta values) of TSS were 51.17% and 41.56% in two distinct protocols varying in operative parameters. The calculated excess sludge reduction ratio was 49.60% with a sludge recirculation ratio of 2, but increased to 68.97% when the sludge recirculation ratio rose to 3. The sludge volume indexes (SVIs) for the control and test processes were 68.4 and 57.0 respectively, indicating the absence of any negative effect of the modification on sludge settling characteristics. Effluent water quality satisfied national legislative requirements.