Wastewater treatment bacteria: biological treatment with measurable results

Fat-containing wastewater from foodservice, catering and food processing burdens municipal treatment plants at multiple levels simultaneously. In the influent area, triglycerides and fatty acids deposit on screen walls and bar screens, forming viscous floating layers. In the aeration tank, fat particles disrupt oxygen transfer — even 15–20 mg/l fat content measurably reduces O₂ transfer. In the digestion tank, insoluble calcium soaps inhibit the methanogenic population and reduce biogas yield.

The sewer stretches between discharge sources and the treatment plant are another critical segment. Fatty acids combine with calcium ions to form calcium soaps (so-called fatbergs), which constrict pipelines and release hydrogen sulphide (H₂S) under anaerobic conditions. H₂S oxidises in moisture to sulphuric acid — the primary cause of concrete corrosion in sewers. Remediation costs for H₂S-damaged sewer sections typically run €800–2,500 per linear metre.

The revised EU Urban Wastewater Treatment Directive (in force since 1 January 2025) tightens requirements for direct dischargers and strengthens the obligations of sewer network operators towards indirect dischargers. Municipalities and water associations that have historically relied on reactive chemical flushing are under increasing pressure to implement preventive, demonstrably effective measures.

A municipal treatment plant's biological stage works with activated sludge — a complex consortium of millions of microorganisms. This sludge is optimised for BOD₅ oxidation and ammonia nitrification. For triglyceride and long-chain fatty acid hydrolysis, however, it is poorly equipped: lipolytic specialists make up less than 1% of total biomass in a typical activated sludge.

The result: fat that enters the influent is barely biologically degraded — it floats, agglomerates and deposits. Mechanical screens and grit channels remove coarse grease, but emulsified and dissolved fatty acids pass these pre-treatment stages unhindered. In the aeration tank, they form hydrophobic layers on activated sludge flocs, disrupting sedimentation and increasing sludge volumes.

This is precisely where targeted application of microbial culture comes in. The concept: by adding high-concentration microbial culture at the influent, fat hydrolysis begins before the aeration tank. Cleaved fatty acids are water-soluble, can be oxidised by the normal activated sludge and do not enter the digester as insoluble lipid aggregates.

lipasanF® is deployed in municipal settings either as continuous dosing in the influent (dosing point: influent shaft or screen bypass) or as shock dosing in shafts with high fat deposition. The concentration of selectively cultivated microbial culture is 10 to 100 times higher than in broad-spectrum bioproducts typically offered for sewer maintenance.

Results from four municipal pilot projects are instrumentally documented. At Amperverband Bavaria, 25 m³ of fat was biologically degraded over 12 weeks — visible as a reduction in floating layer thickness in the influent shaft and primary clarifiers. At LINEG water association in North Rhine-Westphalia, fat content in the monitored sewer section fell by 40–60%. In Groß-Gerau and Pfungstadt, a measurable decrease in H₂S concentration and odour complaints in the surrounding residential area was additionally documented.

In practice: a pilot phase with an accompanying measurement programme can be set up with minimal effort — define dosing points, record baseline parameters (floating layer height, COD, influent fat content, H₂S concentration) and measure over 8–12 weeks. Lipobak supports this process from the outset and provides the documentation required by regulatory authorities and associations.