Arla Foods Vimmerby Dairy Wastewater
A documented rotating-disc sidestream MBR for variable milk-powder and CIP wastewater
This case study concerns the milk-powder factory at Vimmerby, Sweden. It is not the same project as Arla’s separately reported Danish wastewater-reuse initiatives. The available technical account is historical, particularly its 2015 operating data, so the page distinguishes reported plant facts from engineering interpretation.
1. Site context and treatment objective
The factory needed additional wastewater capacity while the receiving municipal treatment plant was already at capacity. The reported municipal upgrade horizon was three to four years, whereas the dairy needed a faster production-supporting solution. The selected prefabricated modular plant was commissioned in approximately six to seven months.
The feed came from milk-powder production and associated clean-in-place (CIP) operations. The case report describes substantial variation in organic and inorganic load, pH, temperature, dissolved solids, and nutrient balance. That variability is central to understanding the design: the MBR was not simply a membrane added after a steady municipal activated-sludge process.
2. Documented process configuration
flowchart TB
A[Milk-powder and CIP wastewater] --> B[Rotating mechanical screen <1 mm]
B --> C[pH and conditional C:P adjustment]
C --> D[Pre-denitrification]
D --> E[Aerobic nitrification]
E --> F{High influent phosphorus?}
F -- Yes --> G[Conditional alum precipitation]
F -- No --> H[No alum addition]
G --> I[Sidestream rotating-disc ceramic MBR]
H --> I
I --> J[Permeate to wetlands]
I --> K[Rejected sludge return to denitrification]The reported membrane system used rotating 0.2 µm ceramic discs. The case author describes mechanical shear from disc rotation rather than relying only on the hydraulic shear of a conventional pumped sidestream loop.
3. Key design and operating decisions
- Fast modular delivery: the prefabricated plant addressed the time constraint created by municipal treatment capacity.
- Upstream variability control: online pH measurement and conditional carbon/phosphorus adjustment were used to keep biological treatment within the required operating envelope.
- Nutrient-responsive control: the reported control strategy used ammonium to influence nitrification/denitrification timing and phosphorus to govern phosphorus-source or alum dosing.
- Membrane protection: the reported operating sequence used filtration for 10–15 minutes followed by a 10-second over-pressure backwash. CEB or CIP was triggered by rising TMP rather than by a generic calendar alone.
4. Historical reported operating data
| Item | Reported case value or description |
|---|---|
| Reported treatment flow | Approximately 400–450 m³/day |
| Membrane | Rotating 0.2 µm ceramic discs; rotating-disc sidestream configuration |
| 2015 average COD | 3,320 mg/L influent; 30 mg/L outlet |
| 2015 average total nitrogen | 249 mg/L influent; 5 mg/L outlet |
| 2015 average total phosphorus | 22 mg/L influent; 0.21 mg/L outlet |
| 2015 average net flux / TMP | 35 LMH at 0.44 bar average TMP |
| Reported cleaning frequency | CEB approximately 3–4 times/month; CIP approximately 1–2 times/year |
| Reported historical energy/cost | 3.32 kWh/m³ total electricity and €0.59/m³ treated water; source-specific historical figures |
5. Outcomes and what they mean
The technical case report states that the plant met its discharge criteria during the two-year observation period despite variable loads, including occasional 20–30% increases in organic load. It also reports that the rapid project delivery allowed production expansion without waiting for municipal works.
6. Limitations and transferability
- The case report describes high dissolved-solids episodes, changes in sludge characteristics, and a period of high fouling that required CIP. The reported 35 LMH net flux was lower than values cited for other installations.
- Sludge handling represented a large share of the reported operating expenditure, and the plant did not have a separate sludge-treatment process beyond membrane dewatering.
- The energy, cost, concentrations, and cleaning frequencies are historical, site-specific values—not universal design targets.
- A new dairy project requires its own equalization, screening, toxicity/CIP review, nutrient-balance assessment, membrane pilot or vendor validation, cleaning strategy, sludge route, discharge permit review, and energy assessment.
7. Transferable lessons for engineers and operators
- Characterize CIP variability by campaign, not only by a single composite sample.
- Use online pH, nitrogen, flow, and relevant phosphorus information to connect biological control to chemical dosing.
- Define membrane cleaning triggers and recovery procedures before commissioning; do not rely on a nominal flux alone.
- Compare rotating-disc and conventional sidestream/immersed alternatives using whole-life energy, sludge, maintenance, spares, and operator capability.