Reliability analyses of activated sludge systems in attaining effluent standards

1993 ◽  
Vol 20 (2) ◽  
pp. 171-179
Author(s):  
Mukesh Sharma ◽  
W. B. Hall ◽  
E. A. McBean
Keyword(s):  
Activated Sludge ◽  
Oxygen Demand ◽  
Point Method ◽  
Aeration Tank ◽  
Design Point ◽  
Effluent Standards ◽  
Activated Sludge System ◽  
First Order Second Moment ◽  
Key Words Reliability ◽  
Activated Sludge Processes

A design-point method, or advanced first-order second-moment technique, is used for reliability-based analyses of activated sludge processes in meeting specified effluent standards. Three non-normal random variables, namely flow, influent biochemical oxygen demand (BOD), and influent suspended solids (SS) concentrations, are utilized in evaluating the performance of the activated sludge system. Two types of failure to attain specified effluent standards are considered, namely BOD failure and SS failure. The reliability of activated sludge system is studied with respect to the volume of the aeration tank using design-point method. Key words: reliability analyses, BOD, activated sludge.

Evaluation of ozonation and cryptic growth for biosolids management in wastewater treatment

1999 ◽  
Vol 39 (10-11) ◽  
pp. 155-158 ◽  
Author(s):  
E. Egemen ◽  
J. Corpening ◽  
J. Padilla ◽  
R. Brennan ◽  
N. Nirmalakhandan
Keyword(s):  
Activated Sludge ◽  
Continuous Flow ◽  
Growth Conditions ◽  
Aeration Tank ◽  
Biomass Growth ◽  
Waste Sludge ◽  
Process Configuration ◽  
Activated Sludge System ◽  
Expensive Problems ◽  
Cryptic Growth

The ultimate disposal of biosolids has been and continues to be one of the most expensive problems faced by wastewater utilities. The objective of this research is to develop a process configuration for reducing the waste sludge generation in an activated sludge plant by promoting cryptic growth conditions (i.e., biomass growth on intracellular products). For this purpose, excess biosolids from a continuous flow activated sludge system were solubilized using ozone as the cell lysis agent, and then returned to the aeration tank. It is hypothesized that growth under such cryptic conditions will result in low net microbial yields, and hence, minimal net solids wastage. The results of these preliminary studies indicate that the proposed process configuration has the potential to reduce the waste sludge production by 40% to 60%.

Fine Bubble Aeration Using a High Density Diffuser System

1992 ◽  
Vol 26 (9-11) ◽  
pp. 2437-2440 ◽  
Author(s):  
K. Thatcher
Keyword(s):  
Activated Sludge ◽  
Oxygen Transfer ◽  
Oxygen Demand ◽  
High Density ◽  
Plant Performance ◽  
Energy Usage ◽  
High Quality ◽  
Transfer Rates ◽  
Fine Bubble ◽  
Activated Sludge Processes

Current developments with the activated sludge processes with highly concentrated effluents highlight the requirement to (a) reduce energy usage (b) promote the production of high quality effluent. Having observed the efforts being made to improve plant performance we became aware that current methods had to be improved. It was also noted that a period of stagnation had occurred in the development of effective aeration systems. Improved aeration methods are needed which would allow for oxygen transfer efficiencies to be greater than 2kg/kWh. Such oxygen transfer rates should be continually variable in line with the oxygen demand prevailing at any given time. In our study of activated sludge plants we found that operational and electrical/mechanical maintenance was proving to be time consuming and very costly. With these problems in mind we have designed and developed the Fine Bubble High Density Diffuser System.

Use of microtox tests for screening industrial wastewater toxicity

1996 ◽  
Vol 34 (10) ◽  
pp. 43-50 ◽  
Author(s):  
Oliver J. Hao ◽  
Shin Chien-Jen ◽  
Lin Cheng-Fang ◽  
Jeng Fu-Tien ◽  
Chen Zen-Chyuan
Keyword(s):  
Activated Sludge ◽  
Oxygen Demand ◽  
Industrial Wastes ◽  
Wastewater Management ◽  
Waste Discharge ◽  
Significant Toxicity ◽  
Microtox Toxicity ◽  
Microtox Test ◽  
Activated Sludge Processes ◽  
The Impact

Conventional parameters such as chemical oxygen demand and suspended solids may not detect toxic compounds present in a variety of industrial wastewaters and treated wastes. Thus, the presence of toxicity in many industrial wastes presents a significant impact on biological wastewater treatment, and exerts adverse effects on receiving waters. Because of their easy technique and rapid turnaround results, the Microtox tests were used in this study to pinpoint unusual wastewaters, evaluate the toxicity reduction through activated sludge processes, observe the impact of excessive chemical addition to meet the transparency standard, and measure the impact of waste discharge on one particular receiving water. It was found that the results of Microtox tests were useful for such purposes; i.e., low COD wastes exhibited high Microtox toxicity; some activated sludge processes removed significant toxicity; and some effluents from coagulation/oxidation processes showed an increased toxicity. The application of the Microtox test to wastewater management is discussed.

Sludge reduction and performance analysis of a modified sludge reduction process

2013 ◽  
Vol 69 (5) ◽  
pp. 934-940 ◽  
Author(s):  
Zhen Zhou ◽  
Weimin Qiao ◽  
Can Xing ◽  
Yingjun Wang ◽  
Chunying Wang ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Nitrogen Concentration ◽  
Oxygen Demand ◽  
Reduction Process ◽  
Ammonium Nitrogen ◽  
Aeration Tank ◽  
Sludge Reduction ◽  
Oxidation Reduction ◽  
Solids Retention ◽  
And Performance

A modified sludge process reduction activated sludge (SPRAS) technology was developed by inserting a sludge process reduction (SPR) module, composed of an aeration tank and a settler, before the activated sludge system was proposed in this study. Compared with the anaerobic/anoxic/aerobic (AAO) process, the SPRAS resulted in a remarkable decrease in sludge production by 76.6%; sludge decay owing to lengthy solids retention time (about 121.5 d) could be the major cause. During the 217-day operation, the oxidation-reduction potential (ORP) (from 54 to −198 mV) and pH (from 7.8 to 5.0) at the bottom of the SPR settler gradually decreased, and low ORP and pH were in favor of sludge reduction in the SPRAS system. The insertion of the SPR module improved the removal efficiencies of suspended solids, chemical oxygen demand and ammonium nitrogen, and total nitrogen concentration in the effluent was reduced from 23.89 ± 4.82 to 14.16 ± 3.98 mg/L by 50% influent bypassing the SPR module. These results indicated that the SPRAS process could produce much less excess sludge and guarantee better effluent quality than the AAO process.

Treatment of farm dairy effluent with hybrid upflow multilayer bioreactor and activated sludge module

2010 ◽  
Vol 61 (7) ◽  
pp. 1683-1690 ◽  
Author(s):  
D. F. Shams ◽  
N. Singhal ◽  
P. Elefsiniotis ◽  
A. Johnson
Keyword(s):  
Activated Sludge ◽  
Oxygen Demand ◽  
Cod Removal ◽  
Synthetic Wastewater ◽  
Aeration Tank ◽  
Dairy Effluent ◽  
Biological Removal ◽  
Operational Variables ◽  
Farm Dairy Effluent ◽  
Good Potential

Biological removal of nitrogen and carbon from farm dairy effluent (FDE) was studied with two laboratory-scale systems following nitrification and denitrification processes. Each system consisted of an upflow multilayer bioreactor (UMBR) as a pre-denitrification unit, an aeration tank (AT) as nitrification unit and a secondary clarifier. The optimization of two operational variables, total hydraulic retention time (HRT) and internal recycle (IR) rate with both real-FDE and a synthetic-wastewater were investigated. First, HRTs of 2, 3, 4 and 5 days were tested with synthetic-wastewater at uniform IR rate. The HRT of 4 days proved optimum with high efficiencies for nitrification (>90%), denitrification (>90%) and total chemical oxygen demand (COD) removal (∼90%). The lowest efficiency was recorded at 2 days HRT with 7% nitrification efficiency. This was followed by experimentation with IR rates of 200%, 300% and 400% on both real-FDE and synthetic-wastewater at optimized HRT. The increase in IR to 300% improved the denitrification potential and overall performance with continuous high nitrification efficiency and COD removal whereas IR of 400% retarded the process. The application of combined UMBR and activated sludge system showed good potential for biological removal of nitrogen from FDE.

Comparative study of membrane bioreactor (MBR) and activated sludge processes in the treatment of Moroccan domestic wastewater

2018 ◽  
Vol 78 (5) ◽  
pp. 1129-1136 ◽  
Author(s):  
S. Kitanou ◽  
M. Tahri ◽  
B. Bachiri ◽  
M. Mahi ◽  
M. Hafsi ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Membrane Bioreactor ◽  
Ceramic Membrane ◽  
Oxygen Demand ◽  
Domestic Wastewater ◽  
Pilot Scale ◽  
Quality Parameters ◽  
Effluent Quality ◽  
Conventional Activated Sludge ◽  
Activated Sludge Processes

Abstract The study was based on an external pilot-scale membrane bioreactor (MBR) with a ceramic membrane compared to a conventional activated sludge process (ASP) plant. Both systems received their influent from domestic wastewater. The MBR produced an effluent of much better quality than the ASP in terms of total suspended solids (TSS), 5-day biological oxygen demand (BOD5) and chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN). Other effluent quality parameters also indicated substantial differences between the ASP and the MBR. This study leads to the conclusion that in the case of domestic wastewater, MBR treatment leads to excellent effluent quality. Hence, the replacement of ASP by MBR may be justified on the basis of the improved removal of solids, nutrients, and micropollutants. Furthermore, in terms of reuse the high quality of the treated water allows it to be reused for irrigation.

scholarly journals Biofloc production in activated sludge system treating shrimp farming effluent

2018 ◽  
Vol 23 (6) ◽  
pp. 1143-1152 ◽  
Author(s):  
Sandra Tedde Santaella ◽  
Maria do Socorro Vale ◽  
Clara Cabral Almeida ◽  
Willame de Araújo Cavalcante ◽  
Alberto Jorge Pinto Nunes ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Oxygen Demand ◽  
Shrimp Farming ◽  
Effluent Treatment ◽  
Nitrogen Compounds ◽  
Suitable Alternative ◽  
Activated Sludge System ◽  
Feed Cost ◽  
Shrimp Feed ◽  
Farming Industry

ABSTRACT The release of wastewater and the shrimp feed cost are the main challenges faced by the shrimp farming industry. An alternative solution to both problems is biofloc production in a unit external to the farm, in an activated sludge system for effluent treatment. The treatment system’s influent was composed of the shrimp farm wastewater supplemented with urea and sugarcane molasses. The results show that the average removal of chemical oxygen demand was 71% and the average biofloc production in the reactor was approximately 1.5g.L-1. Adding molasses to the influent contributed to the increase in the quantity and diversity of existing microorganisms that are beneficial to cultured shrimp. The mass balance of nitrogen compounds confirmed that nitrification occurred in the system. Therefore, the use of the activated sludge system is a viable and environmentally suitable alternative to produce bioflocs and shrimp farming effluent treatment.

Optimisation and Uprating of Activated Sludge Plants by Efficient Process Design

1988 ◽  
Vol 20 (4-5) ◽  
pp. 121-132 ◽  
Author(s):  
B. Chambers ◽  
G. L. Jones
Keyword(s):  
Mathematical Model ◽  
Activated Sludge ◽  
Plug Flow ◽  
Oxygen Demand ◽  
Full Scale ◽  
Aeration Tank ◽  
Effluent Quality ◽  
Integration Techniques ◽  
In Series ◽  
The Uk

Requirements to improve effluent quality and reduce operating costs at existing activated sludge plants in the UK have led to the development of an accurate mathematical model of the process which can be used for full-scale design. The WRc Activated Sludge Model has been developed over a number of years and is based on the concept of describing the kinetics of BOD removal by including a Monod term for growth and a Michaelis-Menten term for enzymatic activity. Since the first formulation of the model, further equations have been added which describe the use of oxygen and nitrate as electron acceptors for the conversion of BOD. The model equations can be used to predict the performance of most configurations of the activated sludge process by using the ‘tanks in series' concept to describe aeration tank mixing characteristics. Solutions to the equations are easily obtained by standard numerical integration techniques using a computer. The software has been written in such a way that the model can be used interactively by a plant designer. Results obtained using the mathematical model have been used to redesign several full-scale activated sludge plants in the UK. In some cases, it has been possible to reduce the energy costs for aeration by 40% whilst maintaining effluent quality by accurately matching the supply of oxygen to the spatially-varying oxygen demand in plug-flow aeration tanks. Bulking sludge problems have also been solved by the conversion of completely-mixed aeration tanks to plug-flow aeration tanks with complementary redesign of the aeration system.

Reduction of chemical oxygen demand in a conventional activated sludge system treating coke oven wastewater

2020 ◽  
Vol 273 ◽  
pp. 122482 ◽  
Author(s):  
Viktória Pitás ◽  
Viola Somogyi ◽  
Árpád Kárpáti ◽  
Péter Thury ◽  
Tamás Fráter
Keyword(s):  
Activated Sludge ◽  
Chemical Oxygen Demand ◽  
Oxygen Demand ◽  
Coke Oven ◽  
Conventional Activated Sludge ◽  
Activated Sludge System

scholarly journals Performance of Novel Contact Stabilization Activated Sludge System on Domestic Wastewater Treatment

2015 ◽  
Vol 19 (2) ◽  
pp. 7
Author(s):  
Andrés Felipe Torres Franco ◽  
Nancy Vásquez Sarria ◽  
Jenny Rodriguez Victoria
Keyword(s):  
Activated Sludge ◽  
Oxygen Demand ◽  
Domestic Wastewater ◽  
Growth Zone ◽  
Pilot Scale ◽  
Ammonia Nitrogen ◽  
Activated Sludge System ◽  
Suspended Growth ◽  
Removal Efficiencies ◽  
Final Effluent

A pilot-scale study was conducted to evaluate a traditional contact stabilization activated sludge system (CSASC) and a modified CSAS (CSASM) treating domestic wastewater. The CSASC system was comprised of a contact reactor (CR), a stabilization reactor (SR) and a secondary settler (SS); the CSASM included a second CR, a second SS (CR2 and SS2), and a modified SR (SRM) divided into four zones: an attached-suspended growth zone which allowed the system to reach an average sludge retention time close to 36 d and favored the occurrence of nitrification; an anoxic zone for denitrification occurrence; an aerated suspended growth zone with a high presence of organic carbon; and an additional aerated suspended growth zone with a high ammonia concentrations environment. The CSASC’s removal efficiencies of chemical oxygen demand (COD) and total ammonia nitrogen (TAN) were respectively 94±4 % and 53±12%; whereas CSASM’s efficiencies were 88±7% for COD and 92±7% for TAN. Concentrations of TAN and NO3 --N in the CSASC’s final effluent were 14.3±5.2 and 5.0±2.9 mg×L-1; and 4.8±4.4 and 9.1±5.8 mg×L-1 in the CSASM’s final effluent. Results demonstrated that the proposed configuration obtained higher nitrogen removal efficiencies than traditional CSAS.</p>

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