scholarly journals Effect of Aluminium Salt Dosing on Activated Sludge Settleability Indicators: A New Settleability Model Development

Water ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 179 ◽  
Author(s):  
Peter Ojo ◽  
Augustine Ifelebuegu
Keyword(s):  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Model Development ◽  
Chemical Precipitation ◽  
Significant Rise ◽  
Volume Index ◽  
Engineering Practice ◽  
Proposed Model ◽  
The Impact ◽  
Sludge Settleability

There has been a significant rise in the use of aluminium salts (Al3+) for the chemical precipitation of phosphates in wastewater treatment plants due to growing stricter regulatory requirements for wastewater effluent release to the environment. The modelling of the settleability of the resultant Al3+ sludge in present engineering practice for design and optimisation are still based on conventional sludge settleability models. This paper describes a novel activated sludge settleability model which is designed to analyse the effects of Al3+ dosing on activated sludge settleability indicators, zone settling velocity (ZSV), and stirred specific volume index (SSVI). The impact of Al3+ dosing concentrations on ZSV and SSVI of full scale activated sludge plant were analysed in the laboratory over a three years’ period and the exponential form of the Vesilind equation was optimised and validated to include alum chemical dosing parameters. The proposed model equation was found to effectively describe the settleability of Al3+ dosed sludge for dosing concentrations range of 0 to 100 mg/L.

Perspectives on modelling micropollutants in wastewater treatment plants

2013 ◽  
Vol 68 (2) ◽  
pp. 448-461 ◽  
Author(s):  
Ludiwine Clouzot ◽  
Jean-Marc Choubert ◽  
Frédéric Cloutier ◽  
Rajeev Goel ◽  
Nancy G. Love ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Wastewater Treatment Plants ◽  
Model Development ◽  
Transformation Products ◽  
Current Status ◽  
Future Research ◽  
Engineering Practice ◽  
Wide Range ◽  
Receiving Waters ◽  
The Impact

Models for predicting the fate of micropollutants (MPs) in wastewater treatment plants (WWTPs) have been developed to provide engineers and decision-makers with tools that they can use to improve their understanding of, and evaluate how to optimize, the removal of MPs and determine their impact on the receiving waters. This paper provides an overview of such models, and discusses the impact of regulation, engineering practice and research on model development. A review of the current status of MP models reveals that a single model cannot represent the wide range of MPs that are present in wastewaters today, and that it is important to start considering classes of MPs based on their chemical structure or ecotoxicological effect, rather than the individual molecules. This paper identifies potential future research areas that comprise (i) considering transformation products in MP removal analysis, (ii) addressing advancements in WWTP treatment technologies, (iii) making use of common approaches to data acquisition for model calibration and (iv) integrating ecotoxicological effects of MPs in receiving waters.

Nitrification preservation in activated sludge during curative bulking chlorination

2003 ◽  
Vol 47 (11) ◽  
pp. 85-92 ◽  
Author(s):  
E. Cotteux ◽  
P. Duchene
Keyword(s):  
Activated Sludge ◽  
Pilot Plant ◽  
Wastewater Treatment Plants ◽  
Oxygen Uptake Rate ◽  
Ammonia Concentration ◽  
Synthetic Wastewater ◽  
Biological Wastewater Treatment ◽  
Simple Method ◽  
Method Of Measurement ◽  
The Impact

The bulking that occurs in biological wastewater treatment plants using activated sludge is very often controlled by the injection of sodium hypochlorite into the return activated sludge (RAS) stream. In the present study undertaken at two pilot plants fed with synthetic wastewater, the impact of the pass frequency of the sludge at the chlorine dosing point on the nitrifying flora is analysed. The pass frequency is one for the pilot plant 1 and two for the pilot plant 2. A dose of chlorine of 4.85 ± 0.05 g/kg/MLVSS per day was applied at both pilots. The preservative effect on nitrifying activity of the lowest concentration of chlorine at the dosing point and therefore of the highest pass frequency was evidenced. Among other tools, a simple method of measurement of the oxygen uptake rate enabled us to monitor the effect of chlorination on nitrification before recording an increase in the ammonia concentration in the bulking.

scholarly journals An Integrated Approach to the Biological Reactor–Sedimentation Tank System

Resources ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 94 ◽  
Author(s):  
Serena Conserva ◽  
Fabio Tatti ◽  
Vincenzo Torretta ◽  
Navarro Ferronato ◽  
Paolo Viotti
Keyword(s):  
Activated Sludge ◽  
Biological Process ◽  
Wastewater Treatment Plants ◽  
Great Influence ◽  
Integrated Approach ◽  
Biological Processes ◽  
Sludge Characteristics ◽  
Activated Sludge System ◽  
Proposed Model ◽  
Tank System

Secondary clarifiers are demanded to separate solids created in activated sludge biological processes to achieve both a clarified effluent and to manage the biological processes itself. Indeed, the biological process may influence the sludge characteristics, and conversely, the settling efficiency of the sedimentation basin plays an important role on the biological process in the activated sludge system. The proposed model represents a tool for better addressing the design and management of activated sludge system in wastewater treatment plants. The aim is to develop a numerical model which takes into account both the conditions in the biological reactor and the sludge characteristics coupled to the hydrodynamic behavior of a clarifier tank. The obtained results show that the different conditions in the reactor exert a great influence on the sedimentation efficiency.

scholarly journals Evaluation of the accuracy of two simple methods for microscopic activated sludge analysis

2018 ◽  
Vol 78 (10) ◽  
pp. 2104-2112
Author(s):  
Mateusz Sobczyk ◽  
Agnieszka Pajdak-Stós ◽  
Edyta Fiałkowska ◽  
Wioleta Kocerba-Soroka ◽  
Joanna Starzycka-Giża ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Wastewater Treatment Plants ◽  
Oxygen Demand ◽  
Microscopic Analysis ◽  
Volume Index ◽  
Sign Test ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Effluent Quality ◽  
Significant Difference

Abstract Biological microscopic analysis is a popular method employed in wastewater treatment plants worldwide for evaluating activated sludge condition. However, many operators still have reservations regarding its reliability. In this study, we evaluated and compared two methods of microscopic sludge investigation: the sludge index (SI) and the Eikelboom–van Buijsen method (EB). We investigated 79 activated sludge samples from nine treatment plants located in southern Poland over a 1-year period. For each sample, sludge volume index values were calculated and compared with the results of evaluation made on the basis of microscopic analysis. Additionally, the effluent quality was analysed in 45 of 79 cases, including investigation of suspended solids, biochemical oxygen demand, chemical oxygen demand, total nitrogen and total phosphorous. The sign test and Wilcoxon matched pairs test showed that a significant difference existed between the two investigated methods. General conclusions from both methods do not provide reliable information concerning nitrogen and phosphorus removal. The EB method had a tendency to be more conservative in its general conclusions than the SI method. Both are highly reliable for estimating activated sludge quality and solid separation properties.

Improvement of the intersection method for the quantification of filamentous organisms: basis and practice for bulking and foaming bioindication purposes

2016 ◽  
Vol 74 (6) ◽  
pp. 1274-1282 ◽  
Author(s):  
Humbert Salvadó
Keyword(s):  
Wastewater Treatment Plants ◽  
Two Dimensions ◽  
Volume Index ◽  
Filament Length ◽  
Improved Method ◽  
Sludge Volume Index ◽  
Filamentous Microorganisms ◽  
Different Types ◽  
Intersection Method ◽  
The Impact

Bulking and foaming phenomena in activated sludge wastewater treatment plants are in most cases related to the abundance of filamentous microorganisms. Quantifying these microorganisms should be a preliminary stage in their control. In this paper, the simplicity of quantifying them based on the intersection method is demonstrated, by redescribing the theory and applying a new improved protocol; new data of interest are also provided. The improved method allows us to use it with stained smears, including epifluorescence techniques. The error that could be made, when considering the distribution of filamentous bacteria in fresh microscope preparations in two dimensions rather than three is negligible. The effect of the different types of filamentous microorganisms on the settleability was also studied. The effect of the total extended filament length on the sludge settleability was shown to depend on the type of filamentous organism and how it aggregates. When these groups of filamentous organisms are found in small aggregations and there is an increase in the number of filamentous organisms, the sludge volume index (SVI) increases proportionally to the filament length. However, when aggregation increases, the impact on the SVI is significantly lower.

A simple empirical model for the clarification-thickening process in wastewater treatment plants

2014 ◽  
Vol 71 (3) ◽  
pp. 366-372
Author(s):  
Y. K. Zhang ◽  
H. C. Wang ◽  
L. Qi ◽  
G. H. Liu ◽  
Z. J. He ◽  
...  
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Empirical Model ◽  
Wastewater Treatment Plants ◽  
Volume Index ◽  
Compression Zone ◽  
Efficient Operation ◽  
Secondary Settling ◽  
Sludge Thickening ◽  
Simple Empirical Model

In wastewater treatment plants (WWTPs), activated sludge is thickened in secondary settling tanks and recycled into the biological reactor to maintain enough biomass for wastewater treatment. Accurately estimating the activated sludge concentration in the lower portion of the secondary clarifiers is of great importance for evaluating and controlling the sludge recycled ratio, ensuring smooth and efficient operation of the WWTP. By dividing the overall activated sludge-thickening curve into a hindered zone and a compression zone, an empirical model describing activated sludge thickening in the compression zone was obtained by empirical regression. This empirical model was developed through experiments conducted using sludge from five WWTPs, and validated by the measured data from a sixth WWTP, which fit the model well (R2 = 0.98, p < 0.001). The model requires application of only one parameter, the sludge volume index (SVI), which is readily incorporated into routine analysis. By combining this model with the conservation of mass equation, an empirical model for compression settling was also developed. Finally, the effects of denitrification and addition of a polymer were also analysed because of their effect on sludge thickening, which can be useful for WWTP operation, e.g., improving wastewater treatment or the proper use of the polymer.

The main wastewater treatment plant of Vienna: an example of cost effective wastewater treatment for large cities

2006 ◽  
Vol 54 (10) ◽  
pp. 79-86 ◽  
Author(s):  
G. Wandl ◽  
H. Kroiss ◽  
K. Svardal
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Nitrogen Removal ◽  
Nutrient Removal ◽  
Process Management ◽  
Wastewater Treatment Plants ◽  
Treatment Plant ◽  
Single Stage ◽  
Volume Index ◽  
Two Stage

Two-stage activated sludge plants succeed in stable treatment efficiency concerning carbon removal and nitrification with far less reactor tank volume than conventional single stage systems. In case of large treatment plants this fact is of great economic relevance. Because of the very small specific volume of these two-stage treatment plants in comparison with low loaded single-stage plants, internal cycles have to be applied to ensure sufficient nitrogen removal. Due to these internal cycles two stage activated sludge plants offer many possibilities in terms of process management which results in new process optimisation procedures as compared to conventional single-stage nutrient removal treatment plants. The proposed extension concept for the Main Treatment Plant of Vienna was validated with pilot plant investigations especially with regard to nitrogen removal where it proved to comply with the legal requirements. The operation of the treatment plant can easily be adapted to changes in temperature and sludge volume index occurring in full scale practice. Sludge retention time and aerobic volume in the second stage are controlled in order to secure sufficient nitrification capacity and to optimise nitrogen removal by means of the variation of the loading conditions for the two stages. The investigations confirmed that the specific two-stage activated sludge concept applied in Vienna is an economically advantageous alternative for large wastewater treatment plants with stringent requirements for nitrification and nutrient removal.

scholarly journals Influence of road salt thawing peaks on the inflow composition and activated sludge properties in municipal wastewater treatment

2021 ◽  
Author(s):  
J. Tauber ◽  
B. Flesch ◽  
V. Parravicini ◽  
K. Svardal ◽  
J. Krampe
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Municipal Wastewater ◽  
Wastewater Treatment Plants ◽  
Road Salt ◽  
Volume Index ◽  
Municipal Wastewater Treatment ◽  
Floc Size ◽  
Floc Structure ◽  
Autotrophic Biomass

Abstract Operational data over 2 years from three large Austrian wastewater treatment plants (WWTPs) with design capacities of 4 million, 950,000 and 110,000 population equivalent (PE) were examined. Salt peaks, due to thawing road salt were detected and quantified by electrical conductivity, temperature and chloride measurement in the inflow of the WWTPs. Daily NaCl inflow loads up to 1,147 t/d and PE-specific loads of 0.26–0.5 kg NaCl/(PE · y) were found. To mimic the plants' behaviour in a controlled environment, NaCl was dosed into the inflow of a laboratory-scale activated sludge plant. The influence of salt peaks on important activated sludge parameters such as sludge volume index, settling velocity and floc size were investigated. Influent and effluent were sampled extensively to calculate removal rates. Respiration measurements were performed to quantify activated sludge activity. Particle size distributions of the activated sludge floc sizes were measured using laser diffraction particle sizing and showed a decrease of the floc size by approximately two-thirds. The floc structure was examined and documented using light microscopy. At salt concentrations below 1 g/L, increased respiration was found for autotrophic biomass, and between 1 and 3 g NaCl/L respiration was inhibited by up to 30%.

scholarly journals The Impact of Aluminium Salt Dosing for Chemical Phosphorus Removal on the Settleability of Activated Sludge

Environments ◽  
2018 ◽  
Vol 5 (8) ◽  
pp. 88 ◽  
Author(s):  
Peter Ojo ◽  
Augustine Ifelebuegu
Keyword(s):  
Activated Sludge ◽  
Settling Velocity ◽  
Treated Wastewater ◽  
Volume Index ◽  
Sem Images ◽  
Sludge Flocs ◽  
Floc Structure ◽  
Aluminium Salt ◽  
Dose Concentration ◽  
The Impact

The use of metal salts like aluminium in the precipitation of phosphorus in activated sludge plants has increased considerably in recent years due to the need to achieve tighter discharge consents for phosphorus in treated wastewater effluent. The impact of aluminium salt (Al3+) dosing on the settleability of activated sludge as a function of zone settling velocity (ZSV) and stirred specific volume index (SSVI) were investigated in batch settleability tests over a three-year period. The results showed that ZSV increased with increasing dose of aluminium salt as SSVI decreased. This trend was observed for dosing concentrations of less than 100 mg/L. At a dose concentration >100 mg/L, the trend was reversed as ZSV decreased and SSVI increased. At dose concentrations of <100 mg/L, Al3+ helped in the bioaggregation of dispersed activated sludge flocs, thereby improving settleability. The surface morphology from the scanning electron microscope (SEM) images indicated that the initial potential of interfloc bridging, open floc formation, and spindly bulking noticed in the undosed activated sludge flocs were remarkably reduced as the flocs became more compacted after Al3+ treatment. At >100 mg/L of Al3+, the sludge settleability started to disintegrate due mainly to surface charge reversal linked to the formation of aluminium hydroxides and the resultant disintegration of the activated sludge floc structure.

Selector Volume in Pulp and Paper Activated Sludge Wastewater Treatment Plants – Bench Scale and Pilot Plant Studies

1994 ◽  
Vol 29 (5-6) ◽  
pp. 303-311
Author(s):  
J. Wessberg ◽  
T. Welander ◽  
M. Jönsson
Keyword(s):  
Activated Sludge ◽  
Pilot Plant ◽  
Wastewater Treatment Plants ◽  
Pulp And Paper ◽  
Volume Index ◽  
Sludge Volume Index ◽  
Bench Scale ◽  
Reference Process ◽  
Kraft Mill

Laboratory activated sludge reactors were operated on effluent wastewater from a kraft mill. Two of the three reactors were initially preceded with a “normal” size aerated selector, 2% of the total aerated volume, with unsatisfactory sludge volume index development. When the selectors were replaced by larger ones, 13% of the aerated volume, the sludge volume index could be kept below 50 ml/g for the selector processes while continuing to be higher and more unstable in the reference process. A pilot plant, operated in situ on the same wastewater, showed a comparable improvement in sludge volume index when its selector, 7% of the total volume, was replaced by one that constituted 13% of the total volume, corresponding to a selector load of 3 g BOD / g VSS * d. According to studies of the COD balance around one bench scale selector, the COD removal mechanism in the selector was respiration/assimilation rather than uptake/storage.

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