Michael Sievers

Effect of ozonation on biodegradability characteristics of surplus activated sludge

The study investigates the effect of sludge ozonation on solid matter species, disintegration properties, sludge components, and solubilization characteristics under different operating conditions. Ozonation of surplus activated sludge samples taken from the secondary settling tank of a domestic wastewater treatment plant indicates that soluble nitrogen, phosphorus and COD concentrations proliferate as a consequence of extending the ozone feeding time. A steady increase both in soluble nitrogen concentration and ratio of organic phosphorus to soluble phosphorus is observed through ozonation where specific ozone doses range between 4 and 11 mg O3/g SS. Combined treatment of chemical oxidation and aerobic biodegradation to surplus activated sludge is also applied to improve the biodegradability of organic matter by partial chemical oxidative pretreatment with as little specific ozone consumption as possible. The partial oxidation by integrated ozonation is operated as a pre-oxidation step for the subsequent biological degradation, due to the fact that the competition with biological degradation in removing biodegradable organic compounds is avoided and most probably a more biodegradable sludge composition is obtained by means of ozonation. Combined treatment of chemical oxidation and aerobic biodegradation conducted to scrutinize the synergic effect of the coupled treatment system reveals that TS and COD removal efficiencies of ozonated sludge samples cannot be improved beyond the third aerobic biodegradation step.

Sludge Dewatering and Aggregate Formation Effects through Taylor Vortex Assisted Flocculation

Abstract For polymer induced flocculation processes, the effects of flow patterns in a gap of a conical stirrer on aggregate formation and subsequent sludge dewatering efficiency were analysed. Different flow regimes were identified by lab scale investigations with model substances and summarized in a Ta and Re number plane. An enhancement of sludge dewaterability for polymer induced flocculation processes was identified through post‐treatment of flocculated sludge aggregates by the specific flow pattern of stable and wavy Taylor vortices. Photo‐optical image analysis of flocculated aggregates shows a clear change of aggregate size distribution with less small particles during aggregate forming by Taylor vortices compared to classical flocculation procedure by stirrer. Results from technical scale dewatering analyses confirmed enhancement of sludge dewatering efficiency for six different dewatering machines using the identified wavy and stable Taylor vortex flow pattern regime.

Improved Sludge Dewaterability for Sequential Ozonation – Aerobic Treatment

Chemical treatment processes such as ozonation have mostly been considered as an efficient way for bio-solids minimization. The improvement of sludge dewatering was more a welcoming side-effect in these sequential processes. However, sometimes the loaded ozone dose to the sludge has a negative effect on dewaterability. This work address the most important issue found — the effect of ozone on sludge dewaterability in a single ozonation processes as well as in a sequential ozonation biological processes. It was found that the maximum sludge dewaterability was achieved with an ozone dose of 0.05 gO3/gTSS. This value was found to be less than the required ozone dosage that leads to sludge disintegration. However, it was observed that the sequential ozone and aerobic treatment allows further strong improvement of dewatering efficiencies.

Effect of ozone pre-treatment on sludge production of aerobic digestion processes

The effect of ozone in a chemical sludge disintegration process was evaluated. Sludge solution chemical oxygen demand (COD), total suspended solids (TSS) and settling were investigated in single and sequential processes. A significant influence of ozone dose on sludge disintegration was observed: ozone was utilised to degrade the soluble organic matter and to destroy cell surfaces and release the cell liquids. For a single ozonation step, we found an optimum ozone dose in the range of 0.008–0.013 g O3/g TSS to give the best COD and TSS removal efficiency. Disintegrated sludge was treated in a sequential process consisting of consecutive ozonation and bio-aeration (i.e. O3 + biological treatment). The tendency was dependent on accumulated ozone, treatment time and operational conditions. An accumulated ozone dose of 0.055 g O3/g TSS in two separate ozonation processes followed by biological treatments led to COD and TSS removal efficiency of 53 and 46.6%, respectively. The removal efficiency was improved by increasing aerobic treatment time and/or by mixing ozonated sludge with non-ozonated sludge. The settling ability of sludge was found to be fast at very low specific ozone doses. An observed tendency was the effect of ozone on cell disintegration and protein liberation. The use of sequential processes improved the settling tendency of sludge.

Aggregate characterisation by using the FlocFormer system to improve sludge dewatering.

In this paper, the influence of the polymer-induced flocculation on undigested sludge dewatering is investigated by image analysis. The mixing of flocculants in a so-called rapid-mixer and the subsequent forming of aggregates is carried out by the FlocFormer system, a new sludge conditioning system. For the mechanical dewatering a decanter device is used. To evaluate the efficiency of the dewatering process, the total solid content (TS) of the dewatered sludge is analysed. The results of this study show that this type of flocculation represents an alternative to improve sludge dewatering of undigested sludge. Compared with the standard conditioning (T-mixer), the FlocFormer leads to a better improvement (1.37 to 3.46%-points) in terms of TS while the rapid-mixer improves the dewatering efficiency only by 0.50 to 1.73%-points. Additionally, by using the FlocFormer conditioning, an optimal polymer dose of 5 g/kg TS has been detected. By increasing the polymer consumption (4-20% above the optimal dose) the dewatering efficiency remains practically constant (TS approximately 26.5%).

Energiewende in der Abwasserbehandlung

Die Energiewende in der kommunalen Abwasserbehandlung in Bezug auf die Elektroenergie ist technisch derzeit nur fur sehr grose Klaranlagen oder Klaranlagenverbunde im Zusammengehen mit thermischer Klarschlammverwertung moglich. Abwasser ist jedoch aufgrund seiner organischen Bestandteile ein Energietrager fur chemisch gebundene Energie. Eine mit Abwasser betriebene bio-elektrochemische Brennstoffzelle wird vorgestellt, die neue Moglichkeiten fur die energetische Nutzung von Abwasser aufzeigt.

Entwässerung von Elbsedimenten — Ein Beispiel für nachhaltigen Ressourceneinsatz

Im Hamburger Hafen lagern sich aufgrund der verlangsamten Fließgeschwindigkeit im Hafenbereich fortlaufend suspendierte Feststo e ab. Die feinen Partikel gelangen überwiegend über die Elbe in den Hafenbereich, während die gröberen Partikel durch die Tide der Nordsee stromaufwärts eingetragen werden. Zur Aufrechterhaltung der notwendigen Wassertiefen für Containerund Kreuzfahrtschi e werden die abgelagerten Sedimente ausgebaggert. Im Jahre 2015 sind insgesamt 8,5 Millionen m3 Baggergut angefallen. Der überwiegende Anteil des Baggerguts ist so gering belastet ist, dass nach den Kriterien des mit der Hamburger Behörde für Umwelt und Energie (BUE) abgestimmten Handlungskonzeptes eine Umlagerung in Hamburg, beziehungsweise nach den Kriterien des Einvernehmens mit SchleswigHolstein eine Verbringung in die Nordsee, möglich ist. Etwa 10 % des Baggerguts sind höher belastet und müssen an Land behandelt und entsorgt werden. Die Entsorgung umfasst abfallrechtlich die Verwertung und die Beseitigung. Dieser Anteil wird von der Hamburg Port Authority AöR (HPA) mit großem Aufwand in der 1993 in Betrieb genommenen METHA-III-Anlage (METHA – Mechanische Trennung von Hafensedimenten) nassmechanisch auf bereitet. Durch diese Baggergutentnahme wird die Elbe um ca. 1/3 der Schwermetallfracht, die Hamburg über den Oberstrom erreicht, entlastet [1]. Die METHA gilt heute noch als aktueller Stand der Technik und war auch Vorbild für andere Anlagen, wie z. B. die 2011 in Betrieb gegangene AMORAS-Anlage im Hafen von Antwerpen.

Ressourcenschonende Abwasserbehandlung – Chemikalien auf Basis nachwachsender Rohstoffe

Biogene Chemikalien erreichen zunehmend auch die Wasserwirtschaft, weil gerade hier das Umweltbewusstsein eine wichtige Rolle spielt. Die Randbedingungen fur deren Herstellung und Anwendung werden anhand von Beispielen aufgezeigt.

Verfahren zur P-Rückgewinnung

In den vergangenen Jahren wurde in Deutschland eine Vielzahl von Verfahren zur Ruckgewinnung von Phosphor aus Sekundarrohstoffen entwickelt und zum Teil bis zur Praxisreife gefuhrt. Eine Ubersicht wird gegeben.

Ozonation of pentylacetate contaminated waters from textile care industry

En este articulo, se evalua el uso del ozono para el tratamiento de aguas contaminadas con pentilacetato. El pentilacetato es un nuevo solvente que se ha comenzado a utilizar en el proceso de limpieza en seco de textiles, debido a sus beneficios economicos. Sin embargo, en la literatura tecnica no existen datos experimentales registrados sobre ozonizacion de aguas contaminadas con pentilacetato. Este articulo presenta resultados experimentales del efecto del pH en la velocidad de eliminacion de pentilacetato de aguas contaminadas a traves de un proceso de ozonizacion. A pH acido, el pentilacetato se elimina mediante una combinacion de simple volatilizacion y reaccion directa con el ozono molecular. Cuando el pH se incrementa, aumenta la velocidad de eliminacion de pentilacetato, mostrando la importancia del mecanismo por radicales libres. La constante de velocidad de reaccion para la eliminacion indirecta del pentilacetato por accion de radicales es de 2,6 x 109 M-1s-1.