Assessment of Biomethane Potential from a Novel Biofilm Based Wastewater Treatment System

Abstract

Wastewater contains various resources and utilized simultaneously in different treatment
compartments before being released into water bodies. Many municipal wastewater treatment
plants are undergoing expansion and reconstruction to meet the stricter effluent requirements
of the urban wastewater treatment directive (2024/3019). This situation is driving a demand for
sustainable solutions characterized by limited footprint, resource efficiency, environmental
friendliness, and cost-effectiveness.
The FramBlik project known as the future biofilm process, demonstrates a combined approach
by integrating a pretreatment pilot plant named Ideal carbon utilization (ICU) and a continuous
biofilm treatment process advancing MBBR (Moving bed biofilm reactor) called CellaTM
Technology, for resource efficient treatment. The FramBlik plant, located at Källby WWTP
(Lund), utilizes the ICU pilot plant to produce a carbon source from the incoming wastewater
and the CellaTM pilot plant to significantly enhance the biological phosphorus removal (Bio-P)
and nitrogen, which are key pollutants in wastewater.
The main focus of the thesis was to assess the methane potential of the Cella sludge from the
novel CellaTM pilot plant. The project comprises two BMP assays. The first assay focused on
Cella sludge with a pretreatment process. To investigate the comparison and effect of methane
potential, the sludge from the pretreatment pilot plant and sludge from the activated treatment
process was also considered. The second assay focussed on the Cella sludge without
pretreatment, where the screened wastewater directly enters the biological treatment plant
without the operation of pretreatment. CellaTM full scale and activated sludge samples from
Svinninge WWTP were also considered for the second assay. The BMP assay was carried out
along with the blank and control samples to validate the results of the methane potential of the
sludge samples. Gas chromatography was used to measure the volume of the biogas produced
during the incubation period. Emptying of the gas was performed when the pressure exceeds
above 2 atm. The nutrient contents present in the mixture was also measured.
The BMP results were expressed as NmL CH4 / g COD and NmL CH4 / g VS. However due to
handling and measurement errors in the COD, this project relies the BMP results primarily on
NmL CH4 / g VS. In assay 1, the average methane yield obtained from Cella sludge samples
was 295 ± 19 NmL CH4 / g VS and the assay 2 Cella sludge samples yielded 380 ± 20 NmL
CH4/ g VS. The Cella sludge sample characteristics from both assay 1 and assay 2 could have
differed in the proportion of easily biodegradable fraction. Specifically, the results of the
characteristics studies indicated that the Cella sludge samples without the operation of
pretreatment contained higher amounts of organic matter compared to the samples collected
when pretreatment was operational. The variation in the organic matter among the each day
Cella sludge samples are likely attributable to inherent variability or could be due to differences
in the loading rate.
The biofilm treatment process exhibited higher average methane yield of 325 ± 10 NmL CH4/
g VS compared to activated sludge treatment process with 200 ± 50 NmL CH4/ g VS as an
average methane yield. This data indicates that the characteristics of the organic matter and the
nature of the sludge influence the methane potential. Nevertheless, more research is needed in
the area of characterization and sludge biodegradability for the biofilm treatment process in the
future.

Popular Abstract

Waste to resources: nowadays, wastewater is no longer considered as waste. From wastewater, we can produce energy from the sludge in the form of biogas and nutrients can be recovered and used as a fertilizer for agriculture. The treated wastewater can be reused for toilet flushing, irrigation and in industries for various purposes. Research is going on for drinking purposes as well. However, the global warming trend is also increasing on the other end. Burning of fossil fuels, deforestation, mining, industrial processes and urbanization contribute to the causes for global warming. The burning of fossil fuels for electricity generation is one of the major causes for the rise in global warming trend. Replacing fossil fuels with biogas is considered a more sustainable approach. Biogas is the renewable gas produced from organic matter present in the wastewater. Anaerobic digestion is a widely used sustainable practice for biogas production. It is defined as degradation of the organic matter present in the substrate using microorganisms to produce biogas under anaerobic conditions.

Wastewater treatment plants combine sludge from the primary treatment (primary sludge) with sludge from the secondary treatment (secondary sludge) along with co-digestion of food or other organic wastes to improve the biogas yield through digestion process. The organic content in the wastes are biodegradable, responsible for biogas production. Many studies have indicated that, due to the lower organic content in the secondary sludge, the overall yield of the biogas potential is reduced. In recent days, secondary sludge from the biofilm treatment process has gained more interest because of its increased energy potential compared to sludge from activated sludge treatment process. Biofilm treatment process utilize support material for biofilm growth, providing efficient organic matter degradation for energypotential.

This master thesis assesses the methane potential of the sludge from a new biofilm based wastewater treatment process called CellaTM Technology. The study compares the methane potential of the sludge obtained from CellaTM Technology with and without primary treatment using biochemical methane potential tests. These tests determines the methane potential of the sludge samples. The volume of methane produced from the mixture during the incubation period was measured and analyzed (See Figure 1). The results indicates that the methane potential of the Cella sludge was higher when primary treatment was not operated compared to the methane potential of the Cella sludge when primary treatment was operated. This research is important for the future to understand the inherent advantages of biofilm systems to maximize the energy and resource recovery. Nevertheless, further characterization and biodegradability studies are necessary in the future for sludge from the biofilm treatment processes to promote environment sustainability.

• author: Murugan, Karthikeyan
• supervisor: Åsa Davidsson; Elin Ossiansson; Maria Piculell
• organization: Chemical Engineering (M.Sc.Eng.)
• course: VVAM01 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Earth and Environmental Sciences
• keywords: Wastewater, Biofilm treatment, Biogas, Methane potential, Water and environmental engineering
• language: English
• id: 9188884
• date added to LUP: 2025-05-22 08:44:49
• date last changed: 2025-05-22 08:44:49