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.

scholarly journals Comparison of the impacts of thermal pretreatment on waste activated sludge using aerobic and anaerobic digestion

2018 ◽  
Vol 78 (8) ◽  
pp. 1772-1781 ◽  
Author(s):  
Hyungjun (Brian) Jo ◽  
Wayne Parker ◽  
Peiman Kianmehr
Keyword(s):  
Anaerobic Digestion ◽  
Activated Sludge ◽  
Oxygen Demand ◽  
Waste Activated Sludge ◽  
Thermal Pretreatment ◽  
Decay Products ◽  
Anaerobic Biodegradability ◽  
Pretreatment Conditions ◽  
The Impact ◽  
Aerobic And Anaerobic

Abstract A range of thermal pretreatment conditions were used to evaluate the impact of high pressure thermal hydrolysis on the biodegradability of waste activated sludge (WAS) under aerobic and anaerobic conditions. It was found that pretreatment did not increase the overall extent to which WAS could be aerobically biodegraded. Thermal pretreatment transformed the biodegradable fraction of WAS (XH) to readily biodegradable chemical oxygen demand (COD) (SB) (16.5–34.6%) and slowly biodegradable COD (XB) (45.8–63.6%). The impact of pretreatment temperature and duration on WAS COD fractionation did not follow a consistent pattern as changes in COD solubilization did not correspond to the observed generation of SB through pretreatment. The pretreated WAS (PWAS) COD fractionations determined from aerobic respirometry were employed in anaerobic modeling and it was concluded that the aerobic and anaerobic biodegradability of PWAS differed. It was found that thermal pretreatment resulted in as much as 50% of the endogenous decay products becoming biodegradable in anaerobic digestion. Overall, it was concluded that the COD fractionation that was developed based upon the aerobic respirometry was valid. However, it was necessary to implement a first-order decay process that reflected changes in the anaerobic biodegradability of the endogenous products through pretreatment.

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.

scholarly journals The Impact of Selected Parameters on the Condition of Activated Sludge in a Biologic Reactor in the Treatment Plant in Nowy Targ, Poland

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2657
Author(s):  
Elwira Nowobilska-Majewska ◽  
Piotr Bugajski
Keyword(s):  
Wastewater Treatment ◽  
Statistical Analysis ◽  
Activated Sludge ◽  
Partial Correlation ◽  
Oxygen Uptake Rate ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Test Results ◽  
Partial Correlation Analysis ◽  
The Impact

The aim of this study was to determine the condition of activated sludge in the biologic reactor located in the collective wastewater treatment plant in Nowy Targ (Poland) based on OUR tests in the aspect of the impact of sludge’s concentration in the biologic reactor and dependence of BOD5/TN and BOD5/TP in wastewater flowing into the biologic reactor. The analysis was conducted based on test results from 61 samples of activated sludge taken from the biologic reactor and 61 samples of wastewater flowing into the biologic reactor. The analysis included the concentration of sludge in the biologic reactor. The following indicators were analyzed in wastewater flowing into the reactor: biochemical oxygen demand (BOD5), total nitrogen (TN) and total phosphorus (TP). The statistical analysis concerning the impact of the analyzed factors on oxygen uptake rate (OUR) tests was developed based on the Pearson’s correlation coefficient and partial correlation of many variables. Based on the results of the partial correlation analysis, nomograms were developed to determine the condition of activated sludge microorganisms (OUR) based on the BOD5/TN and BOD5/TP connection and knowledge of the sludge concentration in the bioreactor of the treatment plant. The presented nomograms can be formulated for each bioreactor based on activated sludge technology related the load of organic and biogenic pollutants in the wastewater flowing into the bioreactor and the concentration of the sludge in the bioreactor.

scholarly journals Mathematical modelling of waste activated sludge thermal disintegration

2018 ◽  
Vol 23 ◽  
pp. 00027
Author(s):  
Sylwia Myszograj ◽  
Magdalena Wojciech
Keyword(s):  
Activated Sludge ◽  
Mixed Models ◽  
Treatment Time ◽  
Oxygen Demand ◽  
Repeated Measurements ◽  
Waste Activated Sludge ◽  
Disintegration Time ◽  
Random Factor ◽  
Factor Measurement ◽  
The Impact

Chemical Oxygen Demand (COD) solubilisation was used to evaluate the impact of thermal pretreatment on the transfer of sewage sludge from particulate to soluble phase. It was gathering the experimental data needed for building of empirical mathematical model describing the relation between applied temperature and time and rate of COD solubilisation and degradation. In view of repeated measurements, in order to describe the relationship between changes in the fraction of dissolved COD and the time and temperature, mixed models have been adopted where by fixed factor measurement conditions have been adopted: time and temperature, while the random factor changes the characteristics of waste activated sludge. Linear and logistic nonlinear mixed models were analyzed. The tests demonstrated that all variables are statistically significant in assessing their impact on the efficiency of liquefaction of sludge. On the basis of the estimated model, the temperature rise of 10°C increases degree of disintegration 1.7% above the average treatment time for 0.5h, by 2.6% for 1 hour, and by 3.9% for 2h. COD values decrease between 3 to 23% at temperatures in the range of 55 to 115°C. At higher temperatures COD was reduced in the range of 32 to 44%. Disintegration time did not have the significant impact on the degradation effect.

The impact of sea water flushing on biological nitrification-denitrification activated sludge sewage treatment process

2002 ◽  
Vol 46 (11-12) ◽  
pp. 209-216 ◽  
Author(s):  
S.M. Yu ◽  
W.Y. Leung ◽  
K.M. Ho ◽  
P.F. Greenfield ◽  
W.W. Eckenfelder
Keyword(s):  
Activated Sludge ◽  
Capital Investment ◽  
Sea Water ◽  
Initial Period ◽  
Sewage Treatment ◽  
Ammonia Nitrogen ◽  
Inhibitory Effects ◽  
Original Design ◽  
Activated Sludge Processes ◽  
The Impact

The process performance of the two largest activated sludge processes in Hong Kong, the Sha Tin and the Tai Po Sewage Treatment Works (STW), deteriorated in the initial period after the introduction of seawater flushing in 1995 and 1996, respectively. High effluent ammonia nitrogen (NH4-N) and total suspended solids (TSS) in excess of the discharge standards resulted from incomplete nitrification and changes in floc characteristics. A desktop study on the inhibitory effects of salinity, particularly on nitrification, was subsequently conducted using the Tai Po STW operating data. To assist the upgrade of the Sha Tin STW a five-month extensive bench-scale investigation on a simple but flexible modified Ludzack-Ettinger configuration with bio-selector was conducted to quantify the inhibitory effects due to the saline concentration. The Sha Tin STW upgrade consists of restoration of its original design capacity (conventional process) of 205,000 m3/day from its currently much reduced capacity as a Bardenpho process. Only the volume of the existing biological process and clarifier is to be utilized. The saline concentration ranges from 3,500 up to 6,500 mg Cl-/L, both daily and seasonally. High and greatly fluctuating saline concentrations have been known to inhibit nitrification. Design consideration should also be given to the peak daily and seasonal TKN loading of up to three times the average. Although the nitrifiers maximum specific growth rate was significantly reduced to a low 0.25 day−1, the inhibition was considered to be tolerable with effluent NH4-N and NO3-N consistently at < 1 and < 6 mg/L. The bio-selector was demonstrated to be efficient in control of sludge foaming and bulking with SVI consistently ≤ 125 mL/g. Results from the IAWQ Model No. 1 and the hydraulic model of the secondary clarifiers allowed overall process capacity maximization. With an anoxic mass fraction of 25-30%, operating sludge age of 9-14 days and SVI ≤ 125 mL/g, both the design requirements and the effluent discharge standards could be met. Without these investigations, an unnecessarily large reaction basin and secondary clarifier volume, and hence capital investment, would have resulted.

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 A Practical Methodology for Forecasting the Impact of Changes in Influent Loads and Discharge Consents on Average Energy Consumption and Sludge Production by Activated Sludge Wastewater Treatment

2021 ◽  
Vol 13 (21) ◽  
pp. 12293
Author(s):  
Catarina Silva ◽  
Maria João Rosa
Keyword(s):  
Wastewater Treatment ◽  
Energy Consumption ◽  
Activated Sludge ◽  
Average Energy ◽  
Oxygen Demand ◽  
Operating Conditions ◽  
Limit Values ◽  
Oxygen Requirements ◽  
The Impact ◽  
Sludge Production

This paper proposes a simple and easy-to-use methodology for forecasting the impact of changes in influent chemical oxygen demand (COD) and in the emission limit values (ELVs) of COD and total nitrogen on average energy requirements for aeration and sludge production by activated sludge wastewater treatment plants (WWTPs). The methodology is based on mass balances of sludge production and oxygen requirements for carbonaceous material biodegradation and/or nitrification, oxygen transfer and aeration equipment efficiency. Using average values of historical data of regular monitoring (water quality and operating conditions) WWTP-specific equations of oxygen requirements, energy consumption and sludge production are derived as a function of influent COD and influent N-total, which may be used to quantify the impact of influent and ELV changes. The methodology was tested in five extended aeration WWTPs for three scenarios established by the utility. The results show that increasing influent COD, from 900 to 1300 mg/L, for example, significantly increases the energy consumption by 49% and sludge production by 53%. For influent 54–68 mg/L N-total, imposing 15 mgN/L ELV results in a 9–26% increase in energy consumption. The COD ELV change studied (season-specific, from 150 mg/L 12 months/year to 125 mg/L 8 months/year to 100 mg/L 4 months/year) increases the energy consumption by 1.8–2.6% and the sludge production by 4.3–5.4%.

scholarly journals Design of Sequencing Batch Reactor (SBR) Treatment Plant for Abattoir Wastewater (A Case of Apa Mmini Stream)

2020 ◽  
pp. 15-21
Author(s):  
Ogbebor Daniel ◽  
Ndekwu, Benneth Onyedikachukwu
Keyword(s):  
Activated Sludge ◽  
Sequencing Batch Reactor ◽  
Settling Velocity ◽  
Batch Reactor ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Treatment Method ◽  
Design Parameters ◽  
Sequence Batch Reactor ◽  
The Impact

Aim: The study aimed at designing a wastewater treatment method for removal of (Biological Oxygen Demand) BOD5 using Sequencing batch reactor (SBR). Study Design: SBR functions as a fill-and-draw type of activated sludge system involving a single complete-mix reactor where all steps of an activated sludge process take place. Methodology: The intermittent nature of slaughterhouse wastewaters favours batch treatment methods like sequence batch reactor (SBR). Attempts to remediate the impact of this BOD5 on the stream, led to the design of a sequence batch reactor which was designed to treat slaughterhouse effluent of 1000 L. Results: The oxygen requirement for effective removal of BOD5 to 95% was determined to be 21.10513 kgO2/d, while L:B  of 3:1 was considered for the reactor. Also, air mixing pressure for the design was 0.16835 bar, while settling velocity was . Conclusion: To ensure proper treatment of BOD5 load of the slaughterhouse, a sequencing Batch reactor of 1000 litre carrying capacity was designed. For effective operation of this design, the pressure exerted by the mixing air was 0.16835 bar which was far greater than the pressure exerted by the reactor content and the nozzle. Settling velocity of 0.0003445 m/s for 0.887 hrs was required for the reactor to be stable and a theoretical air requirement of 1.6884 m³/d was calculated. Hence the power dissipated by the rising air bubbles to ensure efficient mixing of oxygen in the reactor was calculated as 26530003.91 Kilowatts. With these design parameters, the high BOD5 load downstream of the river can be treated to fall below the FMEnv recommended limit of 50 mg/l.

Continuous treatment of flotation collector wastewater using a membrane bioreactor

2016 ◽  
Vol 73 (8) ◽  
pp. 1901-1909 ◽  
Author(s):  
Weixiong Lin ◽  
Yongkang Dai ◽  
Chun Wu ◽  
Pingting Xu ◽  
Jie Ren ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Extracellular Polymeric Substances ◽  
Tricarboxylic Acid Cycle ◽  
Reduction Rate ◽  
Oxygen Demand ◽  
Continuous Treatment ◽  
Treatment Technology ◽  
Time Period ◽  
Simulated Wastewater ◽  
The Impact

Aniline aerofloat (DDA) is a widely used material in China and has become a main pollutant in floatation wastewater. In this study, a membrane reactor (MBR) was constructed to continuously treat simulated wastewater contaminated with DDA. The study investigated the hydraulic retention time (HRT) and the impact of influent DDA concentration on MBR performance, and analyzed intermediates from the DDA biodegradation pathway and activated sludge transfer pathway. The results showed that a 3 h HRT was an efficient and economical time period for MBR to remove 95 ± 5 mg/L DDA from the simulated wastewater; the chemical oxygen demand reduction rate was 89.9%. DDA concentration negatively impacted MBR performance. MBR performance fluctuated slightly when HRT was 3 h, dissolved oxygen ranged from 4.8 to 5.3 mg/L, pH was between 6.5 and 7.0, and DDA concentrations were at 95 ± 5 mg/L DDA. The transfer pathway in the activated sludge of DDA was through soluble microbial products, loosely bound extracellular polymeric substances, tightly bound extracellular polymeric substances, and finally cell biodegradation. DDA initially degraded to aniline; the aniline was further biodegraded to other organic compounds and was finally mineralized through the tricarboxylic acid cycle. This study offers a new continuous biological treatment technology to address DDA.

The impact of slowly biodegradable organic compounds on the oxygen uptake rate in activated sludge systems

2013 ◽  
Vol 69 (6) ◽  
pp. 1136-1144 ◽  
Author(s):  
J. Drewnowski
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Treatment Plant ◽  
Oxygen Demand ◽  
Oxygen Utilization ◽  
Batch Tests ◽  
Hydrolysis Process ◽  
Major Discrepancy ◽  
The Impact ◽  
Activated Sludge Systems

The hydrolysis process of slowly biodegradable substrate (XS) has an impact on the efficiencies of nutrient removal in activated sludge systems. Measurement of oxygen utilization rates (OURs) and corresponding chemical oxygen demand (COD) is accepted as a very useful tool to reflect the consumption of biodegradable substrates. The influence of the SS fraction in biological wastewater treatment systems has been extensively investigated, but little information is known about the effects of XS on OUR. The aim of this study was to determine the immediate effects of particulate and colloidal (XS) biodegradable compounds on oxygen utilization for a full-scale process mixed liquor from a large wastewater treatment plant located in northern Poland. Since it is difficult to distinguish XS in a direct way, a novel procedure, based on the standard batch tests, was developed and run in parallel reactors with settled wastewater (SWW) and pretreated SWW samples. Two types of aerobic OUR experiments with low and high substrate/biomass (S0/X0 ratio) concentration, were carried out with the SWW without pretreatment, and pretreated with a coagulation–flocculation (C–F) method. The removal of colloidal and particulate fractions by C–F resulted in reduced process rates. The major discrepancy in the rate reductions (over 300% referred to the OURmax) was observed during the OUR batch test with high S0/X0 ratio.

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