Precipitation of Ferric Phosphate in Activated Sludge: A Chemical Model and Its Verification

1989 ◽  
Vol 21 (4-5) ◽  
pp. 325-337 ◽  
Author(s):  
Cornelia Luedecke ◽  
Slawomir W. Hermanowicz ◽  
David Jenkins
Keyword(s):  
Activated Sludge ◽  
Adsorption Mechanism ◽  
Solubility Product ◽  
Ferric Hydroxide ◽  
Phosphate Removal ◽  
Chemical Model ◽  
Additional Mechanism ◽  
Ph Values ◽  
Ferric Phosphate ◽  
Proposed Model

A chemical model of ferric phosphate precipitation was developed describing ferric hydroxy-phosphate precipitation either alone or together with ferric hydroxide. Conditions for formation of one or two precipitates are examined. The model also incorporates an additional mechanism for phosphate removal through adsorption of PO43− ions on the precipitate. Experimental verification of the proposed model was carried out in lab-scale batch and continuous activated sludge units fed with municipal primary effluent and at five pH values in the range of 6.5 to 8.0. Solubility of ferric phosphate in the activated sludge system was significantly different from that reported in the literature for distilled water systems and was pH-dependent with a minimum at pH of approx. 7.0. It is proposed that the composition of precipitating ferric hydroxy-phosphate can be represented by the empirical formula Fe2.5PO4(OH)4.5. Corresponding solubility product was estimated at pKsp=96.7. The adsorption mechanism has an important effect on total phosphate removal, especially at low residual phosphate concentrations.

Nitrate and Phosphate Removal by Co-immobilized Chlorella pyrenoidosa and Activated Sludge at Different pH Values

2003 ◽  
Vol 38 (3) ◽  
pp. 541-551 ◽  
Author(s):  
Guolan Huang ◽  
Yuan Wang
Keyword(s):  
Activated Sludge ◽  
Removal Efficiency ◽  
Ph Value ◽  
Nitrate Removal ◽  
Chlorella Pyrenoidosa ◽  
Phosphate Removal ◽  
Ph Values ◽  
Pva Gel ◽  
Influence Of Ph ◽  
Immobilization Method

Abstract A new immobilization method, the simplifying modified polyvinyl alcohol (PVA)-sulfate method, has been evaluated. The influence of pH value on nitrate and phosphate removal by co-immobilized Chlorella pyrenoidosa and activated sludge was studied. The results showed that the co-immobilized system was adaptable to the environment; the micro-algae reproduced rapidly inside a PVA gel carrier under pH ranging from 5.0 to 10.0. Phosphate removal efficiency of the co-immobilized system was distinctly affected by pH but nitrate removal efficiency was not affected very much. The co-immobilized system had a higher removal efficiency in the water when close to neutral. Under suitable circumstances, the removal efficiency of nitrate reached 80% in all four experimental periods; meanwhile, the highest removal efficiency of phosphate was 88% but decreased to 56% from the first period to the fourth period in the experiment.

Combined Chemical and Biological Removal of Phosphate in Activated Sludge Plants

1991 ◽  
Vol 23 (4-6) ◽  
pp. 611-621 ◽  
Author(s):  
Laurraine H. Lötter
Keyword(s):  
Activated Sludge ◽  
Current Literature ◽  
Nutrient Removal ◽  
Biological Process ◽  
Phosphate Removal ◽  
Ferric Sulphate ◽  
Laboratory Studies ◽  
Batch Studies ◽  
Biological Removal ◽  
Ferric Phosphate

Biological phosphate removal has been achieved in nutrient removal plants in Johannesburg by generating the required substrate for the process. Substrate generation has taken place by primary fermentation and subsequent elutriation. This technique, coupled with control of nitrate return to the anaerobic zone, has allowed phosphorus to be removed almost exclusively by biological means in plants designed for nutrient removal. However, operational problems with primary sedimentation tanks being used for fermentation, for which they were not designed, necessitated the occasional use of chemicals in the Northern Works plant. Contrary to current literature, the addition of ferric sulphate to this plant resulted in inhibition of polyphosphate storage; the cornerstone of the biological process. Laboratory batch studies revealed that iron-treated activated sludge showed a lower propensity for ferric phosphate precipitation than an untreated sludge. These laboratory studies were borne out by practical experence on two extended aeration plants, not designed for nutrient removal. The performance of these plants with different chemicals is discussed and possible reasons are advanced for some of the plant observations.

Operational Results of the Wolfsburg Wastewater Treatment Plant

1992 ◽  
Vol 25 (4-5) ◽  
pp. 203-209 ◽  
Author(s):  
R. Kayser ◽  
G. Stobbe ◽  
M. Werner
Keyword(s):  
Wastewater Treatment ◽  
Activated Sludge ◽  
Nitrogen Content ◽  
Total Nitrogen ◽  
Nitrogen Removal ◽  
Wastewater Treatment Plant ◽  
Treatment Plant ◽  
Phosphate Removal ◽  
Total Nitrogen Content ◽  
Activated Sludge Process

At Wolfsburg for a load of 100,000 p.e., the step-feed activated sludge process for nitrogen removal is successfully in operation. Due to the high denitrification potential (BOD:TKN = 5:1) the effluent total nitrogen content can be kept below 10 mg l−1 N; furthermore by some enhanced biological phosphate removal about 80% phosphorus may be removed without any chemicals.

scholarly journals Turbidity Changes during Carbamazepine Oxidation by Photo-Fenton

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 894
Author(s):  
Natalia Villota ◽  
Cristian Ferreiro ◽  
Hussein A. Qulatein ◽  
Jose M. Lomas ◽  
Jose Ignacio Lombraña
Keyword(s):  
Ferric Hydroxide ◽  
Coordination Complexes ◽  
Strong Increase ◽  
H2o2 Concentration ◽  
Iron Species ◽  
Ph Values ◽  
Carboxylic Groups ◽  
Main Decomposition ◽  
High Turbidity ◽  
Catalyst Dosage

The objective of this study is to evaluate the turbidity generated during the Fenton photo-reaction applied to the oxidation of waters containing carbamazepine as a function of factors such as pH, H2O2 concentration and catalyst dosage. The results let establish the degradation pathways and the main decomposition byproducts. It is found that the pH affects the turbidity of the water. Working between pH = 2.0 and 2.5, the turbidity is under 1 NTU due to the fact that iron, added as a catalyst, is in the form of a ferrous ion. Operating at pH values above 3.0, the iron species in their oxidized state (mainly ferric hydroxide in suspension) would cause turbidity. The contribution of these ferric species is a function of the concentration of iron added to the process, verifying that the turbidity increases linearly according to a ratio of 0.616 NTU L/mg Fe. Performing with oxidant concentrations at (H2O2) = 2.0 mM, the turbidity undergoes a strong increase until reaching values around 98 NTU in the steady state. High turbidity levels can be originated by the formation of coordination complexes, consisting of the union of three molecules containing substituted carboxylic groups (BaQD), which act as ligands towards an iron atom with Fe3+ oxidation state.

Observations Supporting Phosphate Removal by Biological Excess Uptake – A Review

1983 ◽  
Vol 15 (3-4) ◽  
pp. 15-41 ◽  
Author(s):  
G v R Marais ◽  
R E Loewenthal ◽  
I P Siebritz
Keyword(s):  
Activated Sludge ◽  
P Uptake ◽  
Phosphate Removal ◽  
Activated Sludge Process ◽  
Biochemical Mechanism ◽  
Paper Briefly ◽  
Uptake And Release

The paper briefly reviews the development of the biological excess removal of phosphorus in the activated sludge process, from 1959 when it was first observed to the present. It concludes by proposing, tentatively, a biochemical mechanism whereby excess P uptake and release can be explained.

Arsenic removal by ferric-chloride coagulation – effect of phosphate, bicarbonate and silicate

2011 ◽  
Vol 64 (5) ◽  
pp. 1046-1055 ◽  
Author(s):  
Dóra Laky ◽  
István Licskó
Keyword(s):  
Adverse Effect ◽  
Arsenic Removal ◽  
Linear Regression Analysis ◽  
Arsenic Concentration ◽  
Ferric Hydroxide ◽  
Multiple Linear Regression Analysis ◽  
Ph Values ◽  
Robust Model ◽  
Coagulant Dosage ◽  
Negative Effect

Jar tests with synthetic water were carried out in order to investigate the effect of phosphate, bicarbonate and silicate on arsenic removal efficiency by in-situ formed ferric hydroxide. Above 12 mg C/L inorganic carbon concentration, the adverse effect of bicarbonate was definite, and resulted in higher remaining arsenic concentration. At all pH values (7.5–7.8) and coagulant dosages (0.84–3.00 mg/L Fe) tested, the negative effect of phosphate on arsenic removal was also evident. In the presence of silicate small ferric-hydroxide colloids were formed, which were able to go through the 0.45 μm pore-size membrane. Compared to silicate-free systems, 2.5–3.5 times higher coagulant dose was needed to achieve the target arsenic concentration in the presence of 14–23 mg/L Si. At higher pH values the adverse effect of silicate was even more significant. All data were merged and multiple linear regression analysis was carried out in order to build up a robust model to predict the residual arsenic concentration if the raw water contains 50–60 μg/L initial arsenic concentration. The estimation was based on the following variables: PO4-P concentration, final pH, Si concentration, Fe(III) dose. The most important influencing factors proved to be the silicate concentration and applied coagulant dosage.

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