Effects of solids concentration on activated sludge deflocculation, conditioning and dewatering

2001 ◽  
Vol 44 (2-3) ◽  
pp. 417-425 ◽  
Author(s):  
L. H. Mikkelsen ◽  
K. Keiding
Keyword(s):  
Activated Sludge ◽  
Apparent Viscosity ◽  
Complete Removal ◽  
Surface Erosion ◽  
Network Structures ◽  
Sludge Reduction ◽  
Digested Sludge ◽  
Solids Concentration ◽  
Anaerobically Digested Sludge

Optimum conditioning of activated sludge in terms of minimum CST was shown to correspond to the complete removal of turbidity, and the increase in turbidity with shear due to e.g. pumping is therefore expected to affect conditioning. The optimum polymer dosage was directly related to the turbidity of activated sludge after two minutes shear, and was considerably lower than the dosage required for charge neutralisation. The turbidity produced by shear increased more than is proportional with solids concentration and was directly related to the apparent viscosity. It is suggested that increasing solids concentration causes increased surface erosion when network structures are broken, and this causes increases in turbidity and required polymer dosage per solids mass. For Åby activated sludge, optimum polymer dosage per solids mass increased by 52% when the solids concentration was increased from 8.2 to 13.7 g SS/l. Modelling of the effect of solids concentration predicts even higher increases in required polymer dosage for higher solids concentrations. This means that reduced thickening prior to pumping and conditioning may be desirable when the hydraulic capacity of the dewatering device is sufficient. Similar trends were observed for an anaerobically digested sludge. For this sludge, reduction of turbidity with FeCl3 reduced the polymer demand.

Ozonation of endogenous residue and active biomass from a synthetic activated sludge

2011 ◽  
Vol 63 (2) ◽  
pp. 297-302 ◽  
Author(s):  
M. -A. Labelle ◽  
A. Ramdani ◽  
S. Deleris ◽  
A. Gadbois ◽  
P. Dold ◽  
...  
Keyword(s):  
Activated Sludge ◽  
Microbial Activity ◽  
Sludge Reduction ◽  
Digested Sludge ◽  
Active Biomass ◽  
Batch Tests ◽  
Coupled Process ◽  
Synthetic Sludge ◽  
Aerobically Digested

Coupling the activated sludge and the ozonation processes is an efficient, although expensive, solution for sludge reduction. A better knowledge of the mechanisms involved in the degradation of various sludge fractions by ozone is needed to optimize the coupled process. The objectives of this study were to determine the biodegradability of ozone-solubilized endogenous residue, the action of ozone on the active biomass and the solubilization yield of these two main sludge fractions. Batch tests were conducted with slug input of ozone stock solution into fresh or aerobically digested synthetic sludge. Biodegradability of the solubilized endogenous residue was increased by ozonation by up to 0.27 g BOD5/g CODi. Ozone caused biomass lysis, as opposed to an increase in maintenance needs, as shown by a correlation between the decrease in microbial activity and viability. Lysis caused by ozonation was associated with a solubilization of 20% of the lyzed cell COD mass. Solubilization yields were of 9.6 and of 1.9 to 3.6 g COD/g O3 for fresh and aerobically digested sludge, respectively. Design of sludge ozonation processes should account for the variability between the solubilization yield and biodegradability of the various sludge fractions.

Sludge drying reed beds

2003 ◽  
Vol 48 (5) ◽  
pp. 101-109 ◽  
Author(s):  
S. Nielsen
Keyword(s):  
Activated Sludge ◽  
Dry Matter ◽  
Wastewater Treatment Plants ◽  
Regional Climate ◽  
Matter Content ◽  
Dry Matter Content ◽  
Digested Sludge ◽  
Anaerobically Digested Sludge ◽  
Sludge Drying ◽  
Full Operation

Sludge reduction occurs by dewatering (draining, evapotranspiration) and mineralization. Sludge from wastewater treatment plants (2,500-125,000 PE) is treated in sludge reed basin systems with 1-18 basins with loading rates of 25-2,200 tons dry matter/year for 10 years. In general, the sludge type is surplus activated sludge or a mix of mesophile digested sludge and surplus activated sludge. Dimensioning and design of reed basin systems for 10-year periods of operation depends on how the sludge is produced, rate of production (tons of dry matter/year), sludge type, quality and regional climate. Loading cycles are related to the sludge type and the age of the sludge reed systems. The period can be divided into a number of operating phases: commissioning, full operation, emptying and re-establishment of the system. Experience shows that efficiency makes special demands on the design of the systems and on the operational control in order to obtain a final dry matter content in the sludge residue of approximately 40% and the number of operating years. Sludge loadings with surplus activated sludge and surplus activated sludge mixed with anaerobically digested sludge amount to a maximum of 60 and 50 kg dry matter/m2.year, respectively.

Mass and Viability Estimations of Nocardia in Activated Sludge and Anaerobic Digesters Using Conventional Stains and Immunofluorescent Methods

1994 ◽  
Vol 29 (7) ◽  
pp. 249-259 ◽  
Author(s):  
Mark Hernandez ◽  
David Jenkins ◽  
Blaine L. Beaman
Keyword(s):  
Activated Sludge ◽  
Anaerobic Digester ◽  
Gram Stain ◽  
Digested Sludge ◽  
Anaerobic Digesters ◽  
Detention Time ◽  
Anaerobically Digested Sludge ◽  
Anaerobic Digester Sludge ◽  
Nocardia Amarae ◽  
Immunofluorescent Method

An immunofluorescent method was developed to estimate the quantity and viability of Nocardia filaments in activated sludge and anaerobically digested sludge on both a mass and volume basis. The Gram stain counting technique of Vega-Rodriguez (1983) and Pitt (1988) was modified to estimate the mass of Nocardia in activated sludge and compared to the immunofluorescent method. Both methods were calibrated on a pure culture of chemostat grown Nocardia amarae. Using the immunofluorescence technique, Nocardia were estimated to comprise an average of 18% by weight of the VSS in a foaming activated sludge plant. Nocardia were found to be, on average, 79% viable as judged by INT reduction staining. Nocardia were found to comprise 13% of the VSS in a foaming anaerobic digester sludge and had an average viability of 63%. These organisms were estimated to be 30 to 50% viable in a mixed anaerobic digester with a hydraulic detention time of 14 days.

Presence of Phenolic Compounds in Sewage, Effluent and Sludge from Municipal Sewage Treatment Plants

1982 ◽  
Vol 14 (4-5) ◽  
pp. 143-150 ◽  
Author(s):  
F B DeWalle ◽  
D A Kalman ◽  
R Dills ◽  
D Norman ◽  
E S K Chian ◽  
...  
Keyword(s):  
Sewage Treatment ◽  
Municipal Sewage ◽  
Sewage Effluent ◽  
Capillary Gc ◽  
Digested Sludge ◽  
Calculated Concentration ◽  
Sewage Treatment Plants ◽  
Anaerobically Digested Sludge ◽  
Final Effluent ◽  
Dimethyl Phenol

A total of 25 municipal sewage treatment plants were sampled, 10 of which were resampled, to determine the quantity of phenolics in the sewage, final effluent and the anaerobically digested sludge using capillary GC/MS/DS/techniques. The study noted in decreasing order of frequency in raw sewage: phenol, pentachloro-phenol, dimethyl phenol, 3-methyl, 4-chlorophenol, 2,4,6-trichloro-phenol, 2,4-dichlorophenol, 2-nitrophenol, 2-chlorophenol, 2,4-dinitro-6-methylphenol and 2,4-dinitrophenol. The maximum concentration of phenol in sewage and sludge was 2800 ppb and 4460 respectively, while similar values for pentachlorophenol were 58 and 1200 ppb. Statistically calculated concentration reductions for phenol and dimethyl phenol were generally greater than noted for tri- and pentachlorophenol. Low decreases or increases were noted for monochlorophenol and especially for dichlorophenol as a result of the chloronation of the final effluent.

Increased Stability of Anaerobic Digestion by Controlled Recirculation

1991 ◽  
Vol 23 (7-9) ◽  
pp. 1229-1237
Author(s):  
Chaio-Fuei Ouyang ◽  
Tain-Gen Chang
Keyword(s):  
Substantial Reduction ◽  
Gas Production ◽  
Digested Sludge ◽  
Significant Saving ◽  
Methane Generation ◽  
Sludge Digestion ◽  
Solids Concentration ◽  
Secondary Sludge ◽  
Sludge Recycling ◽  
Growth System

The treatment characteristics of municipal sludge were investigated by the anaerobic activated sludge digestion (AASD) system. This study used the suspended growth system and mesophilic temperature in the digestors and separators; the system achieves a more stable and improved process; such a process configuration offers the possibility of a substantial reduction in the total volume necessary for efficient stabilization. This study presents data indicating that the AASS system is feasible. In general, with an applied solids concentration of TS= 2%, the nonbiodegradable portion of the substrate concentration contained in the primary and secondary sludge was found to be 40.6% and 35.1% on the basis or TVS and COD, respectively. This study also provides evidence that the reactions at a recycling ratio of R=1 and R=3 are considerably more stable than those achieved in conventional or other recycling ratio digestors with a HRT of 9 days or longer. The gas production and bioactivity is also higher than that normally produced by the conventional single-stage digestion system. The experimental results also indicate that the dilution rate exceeds the maximum specific growth rate as the HRT is decreased from 9 days to 6 days. The significant saving in reactor volume and enhanced methane generation should offset the energy required for digested sludge recycling.

Characterization of raw sludge, chemically modified sludge and anaerobically digested sludge in Hong Kong

1998 ◽  
Vol 38 (2) ◽  
pp. 25-32 ◽  
Author(s):  
C. W. Chu ◽  
C. S. Poon ◽  
R. Y. H. Cheung
Keyword(s):  
Hong Kong ◽  
Sewage Treatment ◽  
Sewage Treatment Plant ◽  
Treatment Plant ◽  
Chemical Properties ◽  
Primary Treatment ◽  
Digested Sludge ◽  
Total N ◽  
Chemically Modified ◽  
Anaerobically Digested Sludge

Chemically Enhanced Primary Treatment (CEPT) or Chemically Assisted Primary Sedimentation (CAPS) is being employed at the new sewage work on Stonecutters Island as part of the Strategic Sewage Disposal Scheme (SSDS) in Hong Kong. CAPS involves the use of chemical coagulants (such as lime or ferric chloride) to induce coagulation or flocculation and let these finely-divided particles form large aggregates (floc) so that they can settle out within a reasonable period of time. In this study, five sludge samples collected from different sewage treatment plants in Hong Kong were physically and chemically characterized. They were chemically modified sludge from Stonecutters Island (CAPS) raw sludge from Tai Po and Yuen Long Sewage Treatment Plant (STP) (rTP & rYL) and anaerobically digested sludge from Tai Po and Yuen Long STP (dTP & dYL). It was found that CAPS sludge was better than other 4 sludge samples in terms of settleability and dewaterability. CAPS sludge contained significant higher amounts (p<0.01) of extractable compounds than other sludges (except NO3− for dTP, NH4+ and PO43− for dYL). The concentration of total N and P in CAPS sludge were significantly higher (p<0.01) than other sludges (except dYL). The concentrations of total Cu, Pb, Ni, Cd, Cr and K in the CAPS sludge were also significantly higher (p<0.01) than other sludge samples. Most of the metals (Cr, Pb, Cr and Zn) in CAPS sludge were associated with the organically-bounded phase. It is concluded that there are significant differences in both physical and chemical properties between the chemically modified sludge and biological treated sludges.

Bioleaching of toxic metals from anaerobically digested sludge without external chemical addition

2021 ◽  
pp. 117211
Author(s):  
Zhiyao Wang ◽  
Gaofeng Ni ◽  
Jun Xia ◽  
Yarong Song ◽  
Shihu Hu ◽  
...  
Keyword(s):  
Toxic Metals ◽  
Digested Sludge ◽  
Anaerobically Digested Sludge
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