Replacement of Secondary Clarification by Membrane Separation—Results with Tubular, Plate and Hollow Fibre Modules

1999 ◽  
Vol 40 (4-5) ◽  
pp. 311-320 ◽  
Author(s):  
Berthold Günder ◽  
Karlheinz Krauth
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Hollow Fibre ◽  
Stable Operation ◽  
Membrane Systems ◽  
Process Technology ◽  
Mixed Liquor ◽  
Activated Sludge Processes

Membrane separation systems can replace the final clarification step to separate mixed liquor suspended solids (MLSS) in the activated sludge processes. Mixed liquor suspended solids concentrations as high as 20 g/l can be obtained compared with the typical 3-4 g/l for conventional activated sludge/secondary clarifier systems. This leads to much smaller reactor volumes. In addition, excellent, solids free effluent qualities can be achieved with this process technology. This paper reports about the parallel investigation of three membrane systems installed within or outside bioreactors of 7 to 9 m3 volume and flow rates from 1 to 3 m3/h. The different membrane modules were investigated: plate module (80 m2 membrane surface), hollow fibre module (80 m2) and tubular module (45 m2). At MLSS concentrations up to 25 g/l and water temperatures from 10 to 25°C a stable operation of the membrane systems was achieved for a period of more than one year. The energy consumption was approximately 1.5 kWh/m3 for the plate and hollow fibre and 3.0 kWh/m3 for the tubular module system.

Replacement of secondary clarification by membrane separation - results with plate and hollow fibre modules

1998 ◽  
Vol 38 (4-5) ◽  
pp. 383-393 ◽  
Author(s):  
Berthold Günder ◽  
Karlheinz Krauth
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Municipal Wastewater ◽  
Hollow Fibre ◽  
Treated Wastewater ◽  
Stable Operation ◽  
Membrane Systems ◽  
Process Technology ◽  
Mixed Liquor ◽  
Activated Sludge Processes

Submerged membrane systems can replace the final clarification step to separate mixed liquor suspended solids (MLSS) from treated wastewater in the activated sludge processes. Mixed liquor suspended solids concentrations as high as 20 g/l can be maintained compared with the typical 3–4 g/l for conventional activated sludge/secondary clarifier systems. This leads to much smaller reactor volumes. In addition, excellent, solid free effluent qualities can be achieved with this process technology. One major challenge, when applying membrane technology to municipal wastewater treatment systems, is handling the flow variations typically encountered by these systems. This paper reports about the parallel investigation of two membrane-systems installed within a 7 m3 and a 9 m3 bioreactor. One membrane system used submerged plate modules (80 m2 membrane surface), the other hollow fibre modules (83.4 m2). The emphasis of this first investigation was the hydraulic performance and elasticity of the membrane systems. At MLSS concentrations of 15 g/l and hydraulic retention times of 6 hours, flux rates of 15 l/m2 h under permanent operation and up to 30 l/m2 h for short periods of time were achieved (standardised to a temperature of 10°C). A stable operation at these rates could be achieved for a full 4 months period without chemical cleaning of the membranes. Future studies will focus on nutrient removal aspects and the energy consumption of the systems.

scholarly journals Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review

Membranes ◽  
2021 ◽  
Vol 12 (1) ◽  
pp. 60
Author(s):  
Arijit Sengupta ◽  
Mahmood Jebur ◽  
Mohanad Kamaz ◽  
S. Ranil Wickramasinghe
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Emerging Contaminants ◽  
Treatment Process ◽  
Membrane Separation ◽  
Membrane Surface ◽  
Membrane Bioreactors ◽  
Size Exclusion ◽  
Wastewater Treatment Process ◽  
Activated Sludge Processes

Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater.

Floc size distribution and bacterial activities in membrane separation activated sludge processes for small-scale wastewater treatment/reclamation

1997 ◽  
Vol 35 (6) ◽  
pp. 37-44 ◽  
Author(s):  
Boran Zhang ◽  
Kazuo Yamamoto ◽  
Shinichiro Ohgaki ◽  
Naoyuki Kamiko
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Membrane Separation ◽  
Small Scale ◽  
Nitrification Rate ◽  
Floc Size ◽  
Denitrification Activity ◽  
Concentration Changes ◽  
Activated Sludge Processes

Activated sludges taken from full-scale membrane separation processes, building wastewater reuse system (400m3/d), and two nightsoil treatment plants (50m3/d) as well as laboratory scale membrane separation bioreactor (0.062m3/d) were analyzed to characterize membrane separation activated sludge processes (MSAS). They were also compared with conventional activated sludges(CAS) taken from municipal wastewater treatment plants. Specific nitrification activity in MSAS processes averaged at 2.28gNH4-N/kgMLSS.h were higher than that in CAS processes averaged at 0.96gNH4-N/kgMLSS.h. The denitrification activity in both processes were in the range of 0.62-3.2gNO3-N/kgMLSS.h without organic addition and in the range of 4.25-6.4gNO3-N/kgMLSS.h with organic addition. The organic removal activity in nightsoil treatment process averaged at 123gCOD/kgMLSS.h which was significantly higher than others. Floc size distributions were measured by particle sedimentation technique and image analysis technique. Flocs in MSAS processes changed their sizes with MLSS concentration changes and were concentrated at small sizes at low MLSS concentration, mostly less than 60 μm. On the contrary, floc sizes in CAS processes have not much changed with MLSS concentration changes and they were distributed in large range. In addition, the effects of floc size on specific nitrification rate, denitrification rate with and without organic carbon addition were investigated. Specific nitrification rate was decreased as floc size increased. However, little effect of floc size on denitrification activity was observed.

Evaluating the treatment performance of a full scale Activated Sludge Plant in Islamabad, Pakistan

2012 ◽  
Vol 7 (1) ◽  
Author(s):  
S. S. Fatima ◽  
S. Jamal Khan
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Wastewater Treatment Plant ◽  
Suspended Solids ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Full Scale ◽  
Operational Parameter ◽  
Mixed Liquor ◽  
Treatment Performance

In this study, the performance of wastewater treatment plant located at sector I-9 Islamabad, Pakistan, was evaluated. This full scale domestic wastewater treatment plant is based on conventional activated sludge process. The parameters which were monitored regularly included total suspended solids (TSS), mixed liquor suspended solids (MLSS), mixed liquor volatile suspended solids (MLVSS), biological oxygen demand (BOD), and chemical oxygen demand (COD). It was found that the biological degradation efficiency of the plant was below the desired levels in terms of COD and BOD. Also the plant operators were not maintaining consistent sludge retention time (SRT). Abrupt discharge of MLSS through the Surplus Activated sludge (SAS) pump was the main reason for the low MLSS in the aeration tank and consequently low treatment performance. In this study the SRT was optimized based on desired MLSS concentration between 3,000–3,500 mg/L and required performance in terms of BOD, COD and TSS. This study revealed that SRT is a very important operational parameter and its knowledge and correct implementation by the plant operators should be mandatory.

Improving nitrogen removal in predenitrification-nitrification biofilters

2004 ◽  
Vol 48 (11-12) ◽  
pp. 419-428 ◽  
Author(s):  
L. Larrea ◽  
A. Abad ◽  
J. Gayarre
Keyword(s):  
Dissolved Oxygen ◽  
Activated Sludge ◽  
Nitrogen Removal ◽  
Suspended Solids ◽  
Complete Removal ◽  
Cod Removal ◽  
Nitrification Rate ◽  
Removal Rates ◽  
N Removal ◽  
Activated Sludge Processes

The effect on NH4-N removal rates in nitrification biofilters of filtered biodegradable COD and particulate COD leaving predenitrification biofilters was studied in a lab scale plant configured with the separated system of biofilters for secondary nitrogen removal from urban wastewaters. Applying a typical COD load of 11 kg/m3.day to the predenitrification biofilter and maximizing its COD removal by adding nitrates or by operating an improved control of the internal recycle, only 60% removal of filtered biodegradable COD was found. This value corresponds to the complete removal of the readily biodegradable substrate (30% of influent filtered COD) and 36% of filtered slowly biodegradable substrate (50% of influent COD). The remaining 64% of the latter entered the nitrification biofilter, causing competition between heterotrophs and nitrifiers for dissolved oxygen in the inner layers of the biofilm. Consequently the nitrification rate had relatively low values (0.5 kgN/m3.d) at 14°C despite using dissolved oxygen levels of 6 mg/l. This behaviour may explain the lower nitrification rates obtained in some cases of nitrification biofilters compared to those in tertiary nitrification after activated sludge processes. The particulate COD entering the nitrification biofilter is associated with the suspended solids leaving the denitrification biofilter which are adsorbed by the external layers of the biofilm, increasing its thickness. The activity of the nitrifiers was affected because of a lack of oxygen when the thickness was left to grow considerably. Therefore no significant particulate COD effect is expected to occur as long as backwashing is carried out with the appropriate frequency.

Clarifier Performance in Activated Sludge Process Treating Pulp and Paper Mill Effluents

1994 ◽  
Vol 29 (5-6) ◽  
pp. 313-328 ◽  
Author(s):  
Sakari Halttunen
Keyword(s):  
Activated Sludge ◽  
Suspended Solids ◽  
Paper Industry ◽  
Paper Mill ◽  
Field Studies ◽  
Pulp And Paper ◽  
Pulp And Paper Mill ◽  
Paper Mill Effluents ◽  
Sludge Settling ◽  
Activated Sludge Processes

High suspended solids concentrations are typical for pulp and paper industry treated effluents. A new clarifier model was developed to find the reasons for this problem. The model clarifier is divided into four different zones: inlet, settling, thickening and separation. In the inlet zone sludge is transported by water flow and neither thickening nor settling will happen. When water velocity decreases the main part of the sludge will settle until it reaches the thickening zone. Thickening will continue until the sludge is pumped away from the clarifier. Concentration increase depends on sludge concentration, time and specific thickening coefficient. The minor part, which is specific to the sludge, enters the separation zone and will either settle in the thickening zone or stay in the effluent. In intensive field studies on 12 different activated sludge processes sludge volume in the clarifier, effluent suspended solids concentrations and sludge settling qualities were examined. Modelled sludge blanket volumes were verified with blanket measurements. Modelled effluent suspended solids were also verified by concentration measurements. Sludge thickening characteristics can be estimated by DSVI. From the data collected two empirical relationships were noticed between sludge settling properties and process operation. Solids concentration in clarified water depends on settling number, which is the mean number of sludge settling during its residence time in the process (sludge age). Sludge settling properties seem to depend on collision load, which is defined as COD-load divided by return sludge biomass flow.

Effect of loading rate and intermittent aeration cycle on nitrogen removal in membrane separation activated sludge process

2002 ◽  
Vol 46 (8) ◽  
pp. 119-126 ◽  
Author(s):  
H. Nagaoka ◽  
C. Kudo
Keyword(s):  
Activated Sludge ◽  
Nitrogen Removal ◽  
Loading Rate ◽  
Membrane Separation ◽  
Organic Loading Rate ◽  
Aeration Tank ◽  
Activated Sludge Process ◽  
Intermittent Aeration ◽  
Organic Loading ◽  
Mixed Liquor

The performance of the submerged membrane separation activated sludge process with intermittent aeration was investigated in a laboratory scale experiment by changing organic loading rate and intermittent aeration cycle. A rectangular PVC tank was used as an aeration tank, in which a flat-sheet type Micro-Filtration membrane made of poly-olefin with a pore size of 0.2 mm was submerged. Organic loading rate to the reactor was set at 0.3 and 0.8 g-TOC/L/day. C/N ratio in the feed was set at around 5.0 for every condition. Aeration cycle was changed from 10 min-10 min (aeration - stop) to 120 min-120 min in different organic loading conditions. Flux through the membrane was set at 0.25 m/day. Membrane fouling proceeded rapidly in 0.8 g-TOC/L/day conditions. However, when organic loading rate was 0.3 g-TOC/L/day, bacterial metabolic substances were degraded rapidly compared to the production, thereby decreasing viscosity in mixed liquor. Nitrogen removal rate was between 60% and 80% for 0.8 g-TOC/L/day loading, and between 50% and 65% for 0.3 g-TOC/L/day loading. And the nitrogen removal was highest in 40 min to 60 min aeration cycle conditions. Too short aeration cycle did not result in sufficiently long anoxic periods for denitrification while too long a cycle resulted in unnecessary anaerobic periods after depletion of nitrate. Intermittent aeration was effective also for decreasing viscosity in mixed liquor.

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