Removal of metals and phosphorus recovery from urban anaerobically digested sludge by electro-Fenton treatment

Abstract Systematic investigations of the acidic dissolution of phosphorus (P), aluminum (Al), iron (Fe), and calcium (Ca) from Al-containing tertiary sludge were carried out in this work. The results were compared with the dissolution behavior of Al-containing anaerobically digested sludge to evaluate the P recovery potential in the form of struvite from tertiary sludge versus anaerobically digested sludge. Additional investigations of synthetically produced Al sludge served as a comparison for the dissolution behavior of P and Al without the influence of other contaminants (metals, biomass). In addition, the acid consumption was analyzed as a function of the target pH during the dissolution. The dissolution efficiency of ortho-phosphate in tertiary and anaerobically digested sludge after acid treatment at pH 2 was ∼90%. The dissolution efficiency of Al and Ca in tertiary sludge was also ∼90% at pH 2, while the release efficiency of Al and Ca in anaerobically digested sludge was lower, ∼70% at pH 2. In tertiary sludge, about 75% of Fe was found dissolved at pH 2, whereas in anaerobically digested sludge this value was higher, ∼90%. Based on the experimental data, it can be concluded that significant dissolution of phosphorus from Al-containing tertiary sludge can take place at pH < 3. The highest sulfuric acid consumption for P dissolution was observed in the case of tertiary sludge at pH 2.

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

Water Science & Technology ◽

10.2166/wst.1982.0094 ◽

1982 ◽

Vol 14 (4-5) ◽

pp. 143-150 ◽

Cited By ~ 22

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.

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

Water Science & Technology ◽

10.2166/wst.1998.0095 ◽

1998 ◽

Vol 38 (2) ◽

pp. 25-32 ◽

Cited By ~ 2

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.

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

Water Research ◽

10.1016/j.watres.2021.117211 ◽

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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Phosphorus recovery as struvite from digested sludge – experience from the full scale

Journal of Environmental Management ◽

10.1016/j.jenvman.2020.111743 ◽

2021 ◽

Vol 280 ◽

pp. 111743

Author(s):

Bart Saerens ◽

Sam Geerts ◽

Marjoleine Weemaes

Keyword(s):

Full Scale ◽

Phosphorus Recovery ◽

Digested Sludge

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A System having a Crystallization Process for Phosphorus Recovery from Methane Fermentation Digested Sludge

KAGAKU KOGAKU RONBUNSHU ◽

10.1252/kakoronbunshu.35.127 ◽

2009 ◽

Vol 35 (1) ◽

pp. 127-132

Author(s):

Kazuaki Shimamura ◽

Tateki Kurosawa ◽

Izumi Hirasawa

Keyword(s):

Crystallization Process ◽

Phosphorus Recovery ◽

Digested Sludge ◽

Methane Fermentation

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through tubing and fittings made of PTFE. Analysis was undertaken by the Warren Spring Laboratory of the Department of Trade and Industry, according to the method described by Bailey and Bedbo rough The results are shown in Table IV. and plotted in Fig. 3. and 4. Table IV. Variation of odour strength of extracted samples with volune of eluted air Volume of air Strength of odour samples passing through (dilutions) sludge before sampling (1/1) Raw sludge Digested sludge 0 154 000 9 900 11.1 53 000 350 22.2 30 600 270 55.6 15 500 190 111 8 200 160 It is clear from these results that there is considerable die-off of odour strength with time, and that, as would be expected, the anaerobic digestion of sludge can reduce the odour potential by at least one order of magnitude. To illustrate the importance of this die-off effect, the results have been re-plotted in Fig. 5. in a cunulative form; that is to say as cumulative percentage of the eventual colour release against volume of air. In the case of the raw sewage sludge, 38% of the ultimate odour was carried in the first odour sample, and 90% of the odour had been extracted by the passage of about 200 1. In the case of the anaerobically digested sludge, the same effect is much more marked; 72% of the ultimate odour was carried by the first sample, and thereafter the strength of the odour fell off very rapidly. There are two possible explanations for this. First, it can be postulated that as it is known that many of the important odorous chemical species are highly volatile, they may be only physically trapped in the sludge, and need little encouragement to transfer to the atmosphere. An alternative explanation concerns the existence of two equilibria. As the vapour/liquid equilibrium is disturbed by the passage of air, the concentration of dissolved compounds in the liquid phase falls, disturbing the ’solid’/liquid equilibrium The kinetics of transfer across this latter phase boundary are much slower than for the liquid/vapour transfer, so that the extraction of odour becomes limited by the rate of diffusion into the liquid phase. Two observations may be cited as evidence for this latter view. First, when sludge is applied to land, there is a rapid tail-off of odour nuisance after spreading. Hie incidence of rain after a dry period is known to result in an increased evolution of odour. Second, in earlier experiments samples of sludge were centrifuged, and the supernatant liquor discarded and replaced by tap water, before being used in the standard odour potential test. Some re-extraction of odour from the samples was rapidly found. In practice, both postulated mechanisms are probably at work, especially if the concept of ’solid/liquid equilibrium’ be extended to

Odour Prevention and Control of Organic Sludge and Livestock Farming ◽

10.1201/9781482286311-64 ◽

1986 ◽

pp. 152-152

Keyword(s):

Liquid Phase ◽

Tap Water ◽

Chemical Species ◽

Liquid Equilibrium ◽

Digested Sludge ◽

Order Of Magnitude ◽

Anaerobically Digested Sludge ◽

Solid Liquid ◽

Kinetics Of ◽

Potential Test

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Induced Magnesium Ammonia Phosphate Precipitation to Prevent Incrustations and Measures for Phosphorus Recovery

Water Practice & Technology ◽

10.2166/wpt.2006.051 ◽

2006 ◽

Vol 1 (3) ◽

Cited By ~ 7

Author(s):

Bernd Heinzmann ◽

Gerd Engel

Keyword(s):

Carbon Dioxide ◽

Ammonium Phosphate ◽

Phosphorus Recovery ◽

Anaerobic Sludge ◽

Digested Sludge ◽

Magnesium Ammonium Phosphate ◽

Limit Values ◽

Precipitation Product ◽

Washing Process ◽

Grass Growth

In 1994 for the first time massive incrustations in the centrifuges treating the digested sludge were detected in some wastewater treatment plants (WWTP’s) of the Berliner Wasserbetriebe, which were, as was found out later, mainly due to the precipitation of white MAP (magnesium ammonium phosphate = struvite) deposits with small portions of different calcium phosphate compounds. The reason for this was the over saturation of the digested sludge and the process water (from the separated centrate of the digested sludge) with carbon dioxide, the spontaneous release of or degassing of carbon dioxide, causing the pH to increase, thus altering the solubility equilibrium, and facilitating crystallisation, resulting in deposits (incrustations) on the walls. Obviously, the wastewater purification process used, with enhanced biological phosphorus removal and concentrated streams of digesting sludge, favours the formation of incrustations during sludge treatment. These incrustations were the cause of a lot of operational problems. To prevent incrustations, modifications in the process engineering technology have been applied after several studies and trials. Deliberate extraction of the CO2, e.g. by air injection through a fine-bubble surface aeration system at the bottom of the digested sludge storage tank just before the centrifuges, causes the pH to rise to approx. 8 and thus to cause induced struvite precipitation. This technology enables a precipitation product suitable for recycling to be generated and separated from the anaerobic sludge using a hydro-cyclone. A subsequent second hydro-cyclone stage allowed a further increase in the P-concentration to approx. 40 kg/m3, giving a yield of phosphorus of 20 %. This corresponds with P-load of approx. 316 kg/day and amounts to 18 % of the P inlet load in the WWTP Waßmannsdorf. It was shown that this experimental process is in principle suitable for the separation of the MAP precipitation product in the anaerobic sludge. A complete washing process for the raw MAP is not yet installed, and furthermore, to find the best sizes of nozzles in the hydro-cyclones and most effective pressures tests will have to be carried out soon at pilot level. A comparison with the minimum nutrients content for different kinds of fertiliser (super-phosphate, dicalcium-phosphate with magnesium, NP-fertiliser) defined by the German Fertiliser Regulations, shows that the precipitated MAP is within the range of other legally certified fertilisers. The MAP showed contaminant levels 5 times or more below the limit values of the German Sewage Sludge Ordinance. The MAP precipitation product is very soluble in different solvents (from ammonium chloride to hydrochloric acid). This implies that the precipitation product can be used as a long term fertilizer. In two test soils having a pH value of 6.6 and 7.1, the MAP precipitation solid was tested using standard ryegrass and showed good phosphorus availability from this material leading to a good grass growth.

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