A pilot-scale evaluation of aerobic–anoxic sludge digestion

A pilot-scale (300 L) evaluation of waste-activated sludge digestion by a cyclical aerobic–anoxic mode of operation was undertaken at ambient liquid temperatures (14–17 °C). Three experimental runs were conducted over a 2-year period. The first run compared the aerobic–anoxic process to a conventional, continuously aerated, digestion process. During the second run, the aerobic–anoxic digester was compared to a lime-supplemented conventional aerobic process. The third run compared two aerobic–anoxic digester units, operating at reduced (50 and 25% of normal) aeration rates during the aerobic period. In addition, basic data from batch tests are outlined and discussed. Results from the various experimental runs indicated numerous potential advantages for the aerobic–anoxic mode of digester operation. The main advantage was that turning the air on and off resulted in volatile solids reduction efficiencies similar to that in the continuously aerated systems. In addition to the potential for significant savings in aeration costs, another benefit of the intermittent aeration mode of operation involved improved supernatant quality of the final, settled effluent. Key words: aerobic digestion, anoxic, intermittent aeration, lime, pilot-scale, Redox potential, sludge, solids reduction.

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Sludge accumulation in polishing ponds treating anaerobically digested wastewater

Water Science & Technology ◽

10.2166/wst.2002.0011 ◽

2002 ◽

Vol 45 (1) ◽

pp. 75-81 ◽

Cited By ~ 4

Author(s):

P. Cavalcanti ◽

A. van Haandel ◽

G. Lettinga

Keyword(s):

Pilot Scale ◽

Important Conclusion ◽

Solids Concentration ◽

Volatile Solids ◽

Useful Life ◽

One Year ◽

Uasb Reactors ◽

Very High ◽

Sludge Accumulation

When ponds are used for wastewater treatment, settleable solids will form a steadily growing bottom sludge layer, which reduces their effective volume. Eventually this sludge must be removed to ensure that the pond maintains the required retention time to keep performing properly. The settleable solids may either be present in the influent or they are formed during the treatment as a result of algal flocculation. An experimental investigation was carried out to evaluate bottom sludge accumulation in a polishing pond used for treatment of UASB effluent. The mass and composition of the bottom sludge formed in a polishing pond was evaluated after the pilot scale pond had been in operation for 1 year and about 60 m3 of digested wastewater had been treated per m3 of pond. The bottom sludge mass represented a solids accumulation of 70 g per m3 of digested wastewater. About half of these solids were the result of settling of influent solids in the first part of the pond, while the other half was attributable to settling of algae, formed in the pond. It is concluded that the bottom sludge growth in a polishing pond is so low, that desludging during the useful life span of the pond will most likely not be necessary. This leads to the important conclusion that excess sludge discharge from UASB reactors (a major factor in operational costs) may be omitted, if a polishing pond is used for post-treatment. The bottom sludge had a high volatile solids concentration (58%) and the macronutrient fractions were also high (3.9% N and 1.1% P of the TSS mass). The bottom sludge was stable and could be dried directly without problems. The hygienic quality of the bottom sludge was very poor: about half the influent helminth eggs during one year of operation were found in the bottom sludge and the faecal coliform concentration was very high.

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Determinant impact of waste collection and composition on anaerobic digestion performance: industrial results

Water Science & Technology ◽

10.2166/wst.2000.0083 ◽

2000 ◽

Vol 41 (3) ◽

pp. 291-297 ◽

Cited By ~ 15

Author(s):

C. Saint-Joly ◽

S. Desbois ◽

J-P. Lotti

Keyword(s):

Anaerobic Digestion ◽

Waste Collection ◽

Biogas Yield ◽

Anaerobic Digestion Process ◽

Digestion Process ◽

Waste Composition ◽

Site Characteristics ◽

Volatile Solids ◽

Biogas Productivity

The performance of the anaerobic digestion process depends deeply on the quality of the waste to be treated. This has been already demonstrated at the lab-scale. The objective of this study is to confirm this result at the industrial scale, with very long representative period and with the same process, the Valorga process. According to the waste quality and the collection type and even with the same conditions of fermentation, the biogas yield can vary by a factor of 1.5 when it is expressed (under normal conditions of pressure and temperature) in m3 biogas/t fresh waste, and by a factor of 2 when it is expressed in m3 CH4/t volatile solids. So, the biogas performance does not characterise a process since it is deeply governed by waste composition. This biogas productivity becomes a pertinent parameter only with consistent and relevant hypothesis and/or analytical results on the waste composition which depends on the collection procedure, the site characteristics and the season.

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February 9 — Dentist Day in Russia

Spravočnik vrača obŝej praktiki (Journal of Family Medicine) ◽

10.33920/med-10-2002-10 ◽

2020 ◽

pp. 78-81

Author(s):

Oksana Rybachok

Keyword(s):

Early Childhood ◽

Oral Cavity ◽

Salivary Glands ◽

Spiritual Development ◽

The Body ◽

Mechanical Processing ◽

Normal Functioning ◽

Digestion Process ◽

Quality Of Food

«Man is what he eats,» these words belong to the great Pythagoras. He meant by these words the connection of the origin of consumed food with the spiritual development of man. In fact, a lot depends on the nature of nutrition, the quality of food and, of course, on the degree of its perception by the body. Digestion process begins not in the stomach, but directly in the oral cavity as a result of mechanical processing of products with teeth and under the influence of the secretion of the salivary glands. That is why healthy teeth are the key to the normal functioning of the whole organism — people should start taking care of their teeth from the early childhood and dentists, who are far from being beloved by everybody and are often carelessly evaded, are called upon to help keep the teeth healthy.

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CHARACTERISATION OF THE NITRIFICATION PROCESS FOR DESIGN PURPOSES

Water Science & Technology ◽

10.2166/wst.1994.0155 ◽

1994 ◽

Vol 30 (4) ◽

pp. 47-56 ◽

Cited By ~ 3

Author(s):

O. Sinkjær ◽

L. Yndgaard ◽

P. Harremoës ◽

J. L. Hansen

Keyword(s):

Kinetic Theory ◽

Nitrification Rate ◽

Experimental Basis ◽

Batch Tests ◽

Mode Of Operation ◽

Nitrification Process ◽

Aerobic Reactor ◽

The City ◽

Specific Evaluation ◽

Aerobic Sludge

Pilot plant experiments have been performed over a period of four years in order to establish an experimental basis for the upgrading of the treatment plants of the city of Copenhagen to nitrogen removal. The design chosen is based on the alternating mode of operation. Nitrification rates have been determined in batch tests on activated sludge extracted from the pilot plants and through the measuring of transient concentrations during the alternating mode of operation in the aerobic reactor. The data have been nonnalised to standard conditions by correcting them according to the kinetic theory. By monitoring the normalised nitrification rate it could be established that the nitrification process was occasionally inhibited. The aerobic sludge age required to maintain nitrification has been estimated. A specific evaluation has been made of the sensitivity of the required sludge age to the oxygen concentration and temperature.

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Pilot-scale Evaluation of AirPrex® for Digestate Treatment

Proceedings of the Water Environment Federation ◽

10.2175/193864717821495807 ◽

2017 ◽

Vol 2017 (1) ◽

pp. 119-138

Author(s):

Blair Wisdom ◽

Brad Van Anderson ◽

Isaac Avila ◽

Troy Gottschalk ◽

Kurt Carson ◽

...

Keyword(s):

Pilot Scale ◽

Scale Evaluation

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A Comparison of Two-Stage and Traditional Co-Composting of Green Waste and Food Waste Amended with Phosphate Rock and Sawdust

Sustainability ◽

10.3390/su13031109 ◽

2021 ◽

Vol 13 (3) ◽

pp. 1109

Author(s):

Edgar Ricardo Oviedo-Ocaña ◽

Angélica María Hernández-Gómez ◽

Marcos Ríos ◽

Anauribeth Portela ◽

Viviana Sánchez-Torres ◽

...

Keyword(s):

Organic Matter ◽

Product Quality ◽

Food Waste ◽

Phosphate Rock ◽

Pilot Scale ◽

Two Stage ◽

Green Waste ◽

Wet Weight ◽

Two Phases

The composting of green waste (GW) proceeds slowly due to the presence of slowly degradable compounds in that substrate. The introduction of amendments and bulking materials can improve organic matter degradation and end-product quality. However, additional strategies such as two-stage composting, can deal with the slow degradation of green waste. This paper evaluates the effect of two-stage composting on the process and end-product quality of the co-composting of green waste and food waste amended with sawdust and phosphate rock. A pilot-scale study was developed using two treatments (in triplicate each), one being a two-stage composting and the other being a traditional composting. The two treatments used the same mixture (wet weight): 46% green waste, 19% unprocessed food waste, 18% processed food waste, 13% sawdust, and 4% phosphate rock. The traditional composting observed a higher degradation rate of organic matter during the mesophilic and thermophilic phases and observed thermophilic temperatures were maintained for longer periods during these two phases compared to two-stage composting (i.e., six days). Nonetheless, during the cooling and maturation phases, the two treatments had similar behaviors with regard to temperature, pH, and electrical conductivity, and the end-products resulting from both treatments did not statistically differ. Therefore, from this study, it is concluded that other additional complementary strategies must be evaluated to further improve GW composting.

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