Process recovery after CaO addition due to granule formation in a CSTR Co-Digester : a tool to influence the composition of the microbial community and stabilize the process?

The composition, structure and function of granules formed during process recovery with calcium oxide in a laboratory-scale fermenter fed with sewage sludge and rapeseed oil were studied. In the course of over-acidification and successful process recovery, only minor changes were observed in the bacterial community of the digestate, while granules appeared during recovery. Fluorescence microscopic analysis of the granules showed a close spatial relationship between calcium and oil and/or long chain fatty acids. This finding further substantiated the hypothesis that calcium precipitated with carbon of organic origin and reduced the negative effects of overloading with oil. Furthermore, the enrichment of phosphate minerals in the granules was shown, and molecular biological analyses detected polyphosphate-accumulating organisms as well as methanogenic archaea in the core. Organisms related to Methanoculleus receptaculi were detected in the inner zones of a granule, whereas they were present in the digestate only after process recovery. This finding indicated more favorable microhabitats inside the granules that supported process recovery. Thus, the granule formation triggered by calcium oxide addition served as a tool to influence the composition of the microbial community and to stabilize the process after overloading with oil

Effects of heat shocks on biofilm formation and the influence on corrosion and scaling in a geothermal plant in the North German Basin

At geothermal plants, process failures often occur due to corrosion and scaling processes. Especially after heat extraction, sulfate reducing bacteria contribute to corrosion processes by producing reduced sulfur compounds. In biofilms containing scales such as iron sulfides, corrosion processes are enhanced. In a mobile bypass system located at the geothermal plant in Neubrandenburg (North German Basin), the influence of biofilm formation on corrosion and scaling was investigated. Short-term heat shocks were successfully tested in the bypass system in order to reduce biofilm formation and thus to diminish corrosion and scaling processes

Influence of microbial processes on the operational reliability in a geothermal heat store : results of long-term monitoring at a full scale plant and first studies in a bypass system

This paper describes microbial metabolic processes that are considered to be relevant for the technical reliability of a geothermal heat store. The study reports on changes of the microbial community composition in geothermal well fluids of different temperatures and after plant downtimes monitored by genetic fingerprinting. Stagnant conditions favored the enrichment of bacteria, sulfate reducers (SRB), and sulfur oxidizers (SOB) in the well. Furthermore higher concentrations of DOC, SO_4_2-, H_2S, and H_2 were detected in the first fluids produced after plant downtime. The increased abundance of SOB indicated oxygen ingress during plant downtime. The interaction of SRB and SOB might have further enhanced corrosion and scaling processes. A mobile bypass system installed at the site will help to understand the processes occurring in the well and to study biofilm formation and corrosion rates at different temperatures

Development of new procedures of process control in waste digesters

Als Beitrag zur Prozessoptimierung der Co-Vergärung wurden Untersuchungen zur Steigerung der Raum-Zeit-Ausbeute von Biogasreaktoren durchgeführt. Das Ziel hierbei war einen Frühwarnindikator für die Prozessstörung „Übersäuerung“ zu entwickeln, um den Prozess der Biogasbildung gezielt zu steuern. Es wurden verschieden Maßnahmen wie die Reduzierung der Raumbelastung und der Einsatz von Additiven wie Natronlauge (NaOH) und Calciumoxid (CaO) untersucht, um den Prozess der Biogasbildung zu stabilisieren. Hierbei zeigte sich, dass CaO besser als NaOH für die Entsäuerung geeignet war. Insbesondere beim Einsatz von CaO konnte eine Aggregatbildung beobachtet werden. Das Calcium, das durch das CaO zugeführt wurde, verursachte Ausfällungen mit langkettigen organischen Säuren (LCFA) und mit Phosphat, das von phosphatspeichernden Organismen (PAO) rückgelöst wurde. Zusätzlich wurde die Abnahme der organischen Säuren in der flüssigen Phase vermutlich durch Adsorption der organischen Säuren an die Ausfällungen, durch die Säureaufnahme der PAO und durch einen Säureabbau in den Aggregaten aufgrund vorteilhafter Milieubedingungen ermöglicht. Aufgrund der besonderen Rolle des Calciums hinsichtlich der Prozessstabilisierung, wurde es auf die Eignung als Parameter zur Prozesssteuerung untersucht. Hierbei stellte sich heraus, dass der Quotient aus der Konzentration an organischen Säuren zur Calciumkonzentration (FWI) sensitiver hinsichtlich einer Prozessstörung war als die untersuchten typischen Prozessüberwachungsparameter. Experimentelle Untersuchungen zeigten, dass der FWI zwischen 3 und 7 Tagen vor dem Eintreten einer Übersäuerung durch signifikante Änderungen in seinem Verlauf warnte. Dieser Zeitraum war für die Einleitung von Maßnahmen zur Stabilisierung des Biogasprozesses ausreichend. Zur Steigerung der Raum-Zeit-Ausbeute wurde die Raumbelastung über den FWI gesteuert erhöht. Hierbei stellte sich heraus, dass ein Zeitintervall von 8 Tagen zwischen zwei Erhöhungen der Substratfracht nicht unterschritten werden sollte. Der Betrieb bei Raumbelastungen von 6,0 und 9,5 kg oTS m-3 d-1 mit Fettanteilen von bis zu 87 % und bei Methanausbeuten von 0,9 m³ (kg oTS)-1 war mit dem Einsatz von CaO als Additiv erfolgreich.As a contribution to the optimization of co-digestion, investigations to increase the space-time-yield of digesters were accomplished. The aim was to develop an early warning indicator in terms of over-acidification to control the process of biogas formation. Different counter measures were undertaken to stabilize the process of biogas formation, including the reduction of the organic loading rate, the addition of sodium hydroxide (NaOH), and the introduction of calcium oxide (CaO). The results showed that CaO was more capable of stabilizing the process than NaOH. The formation of aggregates was observed particularly when CaO was used as the additive. The cal-cium, which was charged by the CaO addition, formed insoluble salts with long chain fatty acids (LCFAs), and caused the precipitation of calcium phosphate compounds. Additionally, the decrease in the amount of accumulated acids in the liquid phase was likely enabled by the adsorption of VFAs by the precipitates, the acid uptake by the PAOs and the degradation of VFAs in the aggregates containing favorable milieu conditions. Due to the special role of calcium in terms of process stabilization, its applicability as control parameter was investigated. The ratio of the concentration of organic acids to the calcium concentration (EWI) was found to be more sensitive in terms of process failures than the investigated typical monitoring parameters. The EWI warned be-tween 3 to 7 days before a process failure took place. Experiments showed that this period was long enough to take action successfully in counter measures to stabilize the process. The EWI was applied to increase the organic loading rate (OLR). The experiments showed that a time interval of 8 days between two increases of the OLR was found to be adequate. At OLRs of 6.0 and 9.5 kg VS m-3 d-1 including up to 87 % of fat, the operation of the biogas formation process with additions of CaO was successful. Although the OLR was as high, the methane yield reached almost its expected range with 0.9 m³ (kg VS)-1

Operational Demo Cases

This deliverable demonstrates the operational status of 10 demo cases deployed in 8 EU Member States and their specific NextGen objectives and CE solutions For each demo case, the deliverable show pictures of the prototypes and pilots installed, introduces the first technical results obtained until M 30 provides the specific KPIs (actual and expected) and the expected next steps per each sit

Störungen des Betriebs geothermischer Anlagen durch mikrobielle Stoffwechselprozesse und Erfolg von Gegenmaßnahmen

In the context of geothermal systems, biofilms can influence mineral formation and material resistance against corrosion. In three geothermal plants with different salinity and temperature, organisms of the sulfur cycle have contributed to process failures. On the cold side of a heat store, the increased diversity and abundance of sulfate reducing bacteria (SRB) revealed their participation in corrosion processes and their contribution to a decline in injection efficiency. In all plants, a temporary ingress of oxygen or nitrate led to an increased abundance of sulfur oxidizing bacteria (SOB) that might have accelerated corrosion. In addition, the increase in SOB abundance led to filter clogging in a cold store. Based on their role in microbial-induced corrosion (MIC), changes in the abundance of SOB and SRB may indicate the cause of failure. Measures to control microbial growth, mineral deposits and corrosion, such as temporary increases in temperature, acidification, and addition of hydrogen peroxide (H_2O_2) and nitrate, were evaluated.In geothermischen Anlagen können Biofilme die Mineralbildung und die Injektivität von Bohrungen sowie die Materialbeständigkeit beeinträchtigen. In drei bezüglich Temperatur und Salinität sehr unterschiedlichen Anlagen waren Organismen des Schwefelkreislaufs an Betriebsstörungen beteiligt: Die erhöhte Abundanz von Sulfat-reduzierenden Bakterien (SRB) auf der kalten Seite eines Wärmespeichers wies auf deren Beteiligung an der Korrosion und der Abnahme der Injektivität hin. In allen Anlagen führte der Zutritt von Sauerstoff bzw. der Eintrag von Nitrat zu einer temporären Zunahme Schwefel-oxidierender Bakterien (SOB) und hat vermutlich Korrosionsprozesse beschleunigt. Außerdem hatte in einem Kältespeicher die temporäre Zunahme der SOB ein Filterclogging zur Folge. Aufgrund ihrer entscheidenden Rolle bei mikrobiell induzierter Korrosion (MIC) weisen Änderungen in der Abundanz von SOB und SRB auf die Ursachen mikrobiell bedingter Störungen hin. Zur Beseitigung der Störungen wurden temporäre Erhöhungen der Temperatur, Säuerungen sowie die Zugabe von Wasserstoffperoxid (H2O2) oder Nitrat in den Anlagen getestet und aus mikrobiologischer Sicht bewertet