Development of Simple and Cost-effective Treatment System for Municipal Wastewater

This study developed an alternative municipal sewage treatment system based on the pilot- and full-scale experiments. This proposed system consisting of upflow anaerobic sludge blanket (UASB) and trickling filter using a polyurethane sponge as packing material. This aerobic process was originally developed and named as a down-flow hanging sponge (DHS). DHS reactors accomplished high process performance during pilot- and full-scale experiments in Japan and other countries. The effluent quality of the DHS reactors was comparable to that of activated sludge systems. Moreover, advantages of DHS reactors include simple operation and maintenance (O&M), no required oxygen supply, small land requirement, and less excess sludge production. Indeed, the estimated energy requirement and excess sludge production of UASB and DHS systems were found to be approximately 75 and 85 % lower than those of conventional activated sludge systems, respectively. The high process performance can be attributed to the fact that the DHS reactor maintains much of the sludge in the reactor at concentrations 5–10 times higher than activated sludge. This indicates that DHS reactors have the potential for use as reliable, affordable, and efficient treatment systems, and can be used widely including developing countries

In situ accessibility of Escherichia coli 23S rRNA to fluorescently labeled oligonucleotide probes

One of the main causes of failure of fluorescence in situ hybridization with rRNA-targeted oligonucleotides, besides low cellular ribosome content and impermeability of cell walls, is the inaccessibility of probe target sites due to higher-order structure of the ribosome. Analogous to a study on the 16S rRNA (B. M. Fuchs, G. Wallner, W. Beisker, I. Schwippl, W. Ludwig, and R. Amann, Appl. Environ. Microbiol. 64:4973–4982, 1998), the accessibility of the 23S rRNA of Escherichia coli DSM 30083T was studied in detail with a set of 184 CY3-labeled oligonucleotide probes. The probe-conferred fluorescence was quantified flow cytometrically. The brightest signal resulted from probe 23S-2018, complementary to positions 2018 to 2035. The distribution of probe-conferred cell fluorescence in six arbitrarily set brightness classes (classes I to VI, 100 to 81%, 80 to 61%, 60 to 41%, 40 to 21%, 20 to 6%, and 5 to 0% of the brightness of 23S-2018, respectively) was as follows: class I, 3%; class II, 21%; class III, 35%; class IV, 18%; class V, 16%; and class VI, 7%. A fine-resolution analysis of selected areas confirmed steep changes in accessibility on the 23S RNA to oligonucleotide probes. This is similar to the situation for the 16S rRNA. Indeed, no significant differences were found between the hybridization of oligonucleotide probes to 16S and 23S rRNA. Interestingly, indications were obtained of an effect of the type of fluorescent dye coupled to a probe on in situ accessibility. The results were translated into an accessibility map for the 23S rRNA ofE. coli, which may be extrapolated to other bacteria. Thereby, it may contribute to a better exploitation of the high potential of the 23S rRNA for identification of bacteria in the future

Use of G3-DHS Bioreactor for Secondary Treatment of Septic Tank Desludging Wastewater

Study was done for the use of the third-generation of downflow hanging sponge (G3-DHS) bioreactor for secondary treatment of septic tank desludging wastewater. The main objective of this study was to evaluate the prospective system of G3-DHS bioreactor to be applied in Indonesia. During experiment, the G3-DHS bioreactor kept a relatively high dissolved oxygen concentration under natural aeration. At a relatively short hydraulic retention (HRT) of 3 h, the G3-DHS bioreactor could remove up to 21% (SD = 15%) of total COD, 21% (SD = 7%) of filtered-COD, 58% (SD = 24%) of unfiltered-BOD, and 33% (SD = 24%) of ammonium removal. The final effluent had an unfiltered-BOD of only 46 mg/L (SD = 20 mg/L) that it was below the Indonesian standard (unfiltered-BOD = 100 mg/L) for thresholds of domestic wastewater treatment plants effluent

Characteristics of Granular Sludge in an EGSB Reactor for Treating low Strength Wastewater

A lab-scale expanded granular sludge bed (EGSB) reactor was operated at 20°C with low strength wastewater (0.6-0.8 g COD/L) for over 200 days. Reactor was inoculated with mesophilic granular sludge. The up-flow velocity was set to 5 m/h by effluent recirculation. The COD loading was increased up to 12 kg COD/m3/day until the day 76, resulting in hydraulic retention time of 1.5 hours. Physical properties (settleability anddiameter) of retainedsludge tended todeteriorate during the first 2-3 months, however sludge settleability kept sufficiently in the later part of experiment due to the reconstruction of granular sludge. The growth yield (Yg) of retained sludge (0.13 g VSS/g COD) was about two times higher than mesophilic and thermophilic granular sludge processes while the endogenous decay constant (Kd) is very low (0.0001/day) as compared with those processes. The sludge retention time of retained sludge reduced from 100 days to 40 days by the reduction of hydraulic retention time from 4 hours to 1.5 hours. Maintenance of 40 days of sludge retention time caused the stable retainment of biomass and the significant increase of methanogenic activity of the retained sludge

Intermittent Effluent Recirculation for the Efficient Treatment ofLow Strength Wastewater by an EGSB Reactor

In order to establish the appropriate methane fermentation technology for low strength wastewater, a 2.0 L EGSB reactor was operated at 20°C with 0.3 - 0.4 g COD/L of sucrose-based synthetic wastewater for 500 days. At the start up period, the reactor was operated in EGSB mode with a 5 m/h up flow velocity by continuous effluent recirculation. However, the EGSB reactor exhibited insufficient COD removal (50-60%) at COD loading of 7.2 - 9.6 kg COD/m3·day due to the low COD concentration in the sludge bed. Therefore, we proposed the new operation mode by switching to UASB mode (without recirculation, 0.7 m/h up flow velocity) for 30 minutes and EGSB mode for 10 minutes in 40 minutes cycle. Moreover we added sodium sulfide to make the low ORP condition. In this operation, COD removal increased dramatically, from 65% to 91%. Additionally, physical properties of the retained sludge were well maintained in this operation mode. Furthermore, the retained sludge possessed appropriate levels of methanogenic activity (0.2-0.4 g COD/g VSS/ day) at 20°C

Unjuk Kerja Down-Flow Hanging Sponge (DHS) Bioreaktor sebagai Secondary Treatment untuk Pengolahan Limbah Domestik

Pencemaran air limbah akan terus bertambah dengan meningkatnya jumlah penduduk dan aktifitas masyarakat. Berbagai proses telah diaplikasikan untuk pengolahan limbah domestik, tetapi umumnya proses-proses tersebut membutuhkan biaya operasi dan perawatan yang relatif mahal. Downflow Hanging Sponge (DHS) telah diusulkan sebagai pemecahan persoalan penanganan limbah domestik untuk negara-negara berkembang. DHS bioreaktor adalah pengolahan limbah secara biologis yang tidak membutuhkan aerator dan mudah dalam pengoperasian. Penelitian ini bertujuan untuk mengevaluasi bioreaktor DHS sehingga dapat diterapkan di Indonesia. Bioreakor DHS dioperasikan dengan hydraulic retention time (HRT) 4 jam. Hasil penelitian menunjukkan DHS bioreaktor mampu mengurangi hingga 34% Chemical Oxygen Demand (COD) total, 33% soluble Chemical Oxygen Demand (COD), 80% Biological Oxygen Demand (BOD) total, dan 65% ammonia