Packaged wastewater treatment plants allow municipalities, industrial sites, hotels and developers to treat wastewater close to where it is produced, using factory-built equipment and limited civil works. Three biological processes dominate the market: the membrane bioreactor (MBR), the moving bed biofilm reactor (MBBR) and the sequencing batch reactor (SBR). Each can produce a good effluent, but they differ in footprint, energy demand, operating effort and the quality of water they deliver. This guide explains how they work, compares them and lists the data you need for a proposal.
How MBR, MBBR and SBR plants work
All three processes break down BOD and COD biologically. They differ in how the biomass is retained and how treated water is separated from it.
MBR: biology plus membrane filtration
A packaged membrane bioreactor combines an aeration tank with submerged hollow-fibre PVDF membranes with a pore size of 0.04 µm. The membranes replace the secondary clarifier: treated water is drawn through the fibres as permeate, while the activated sludge stays in the tank. A typical line comprises fine screening, an anoxic zone for denitrification, the aeration tank, the membrane tank and sludge handling. Our MBR package units cover capacities from 5 to 5,000 m³/day.
MBBR: biofilm on moving carriers
In a moving bed biofilm reactor the biomass grows on polyethylene carriers with a specific surface area of 500 m²/m³. The carrier fill ratio is typically 25–67% of the tank volume, and hydraulic retention times are short at around 0.5–4 hours. A pure MBBR needs no sludge recirculation, but the treated water still requires a downstream solids separation step such as a clarifier. More detail is available on our MBBR package units page.
SBR: all steps in one tank
A sequencing batch reactor carries out all treatment steps in a single tank, in an automated cycle of fill, react, settle and decant. The cycle time is adjustable between 3 and 8 hours, and a PLC controls the sequence and adjusts aeration intensity based on dissolved oxygen measurement. Our SBR package units are designed for 50 to 10,000 m³/day.
Effluent quality and footprint
For most buyers the decisive question is what has to leave the plant. MBR delivers the highest and most consistent quality: BOD below 5 mg/L, TSS below 1 mg/L and more than 4-log bacteria reduction, with total nitrogen below 10 mg/L when an anoxic zone is included and total phosphorus below 1 mg/L with chemical precipitation. This makes a compact MBR system the natural choice where water is to be reused for irrigation or toilet flushing, usually after UV disinfection.
A well-designed SBR also reaches BOD below 5 mg/L, with total nitrogen below 8 mg/L and total phosphorus below 1 mg/L when the enhanced biological phosphorus removal (EBPR) cycle is used. MBBR achieves good BOD and nitrogen removal at high volumetric rates; the final level of suspended solids depends on the separation step that follows the reactor.
In terms of footprint, MBR is the smallest option: packaged MBR systems need up to 60% less space than conventional activated sludge plants. MBBR can save up to 60% tank volume compared with conventional activated sludge, which is why it is popular for upgrading existing tanks. SBR saves area by combining reactor and clarifier in one tank, although continuous inflow requires a buffer tank or several reactors operating in turn.
Energy, operation and sludge
Aeration is the largest energy consumer in all three processes. MBBR typically uses 0.3–0.8 kWh per m³ treated. MBR plants generally need more energy because, in addition to process air, the membranes are scoured with air to limit fouling and permeate pumps are required. SBR energy demand is moderate and can be reduced further by controlling aeration on dissolved oxygen.
Efficient air supply makes a measurable difference. Fine-bubble membrane aerators with bubbles of 1–3 mm achieve a standard oxygen transfer efficiency of 6–8% per metre of submergence, considerably more than coarse-bubble systems.
On the air generation side, turbo blowers with variable-speed direct drive achieve up to 40% energy savings compared with fixed-speed rotary lobe blowers.
Operating effort differs as well. MBR membranes rely on automated relaxation and backpulse, periodic chemically enhanced backwash with sodium hypochlorite or citric acid and, eventually, module replacement. Replacement MBR/UF membrane modules are available for major OEM systems such as Toray, Kubota, Memcor and Koch PURON.
MBBR is the most forgiving process: the carriers have an indefinite service life and the biofilm returns to performance quickly after shock loads. SBR, by contrast, depends entirely on its control system, so reliable instrumentation and automation with remote monitoring are essential.
Sludge production also differs. MBR operates at a long sludge retention time of 15–30 days, which tends to produce less and better stabilised excess sludge. In an SBR the sludge settles in the reactor and excess sludge is withdrawn at the end of a cycle. In an MBBR, excess biomass sloughs off the carriers and is removed in the downstream separation step.
MBR vs MBBR vs SBR at a glance
| Criterion | MBR | MBBR | SBR |
|---|---|---|---|
| Effluent BOD | < 5 mg/L | Good, depends on design | < 5 mg/L |
| Suspended solids | < 1 mg/L | Depends on separation step | Depends on settling |
| Nitrogen | TN < 10 mg/L (with anoxic zone) | Nitrification 0.5–1.5 g NH₄-N/m²/day | TN < 8 mg/L |
| Phosphorus | < 1 mg/L (chemical precipitation) | Chemical precipitation if required | < 1 mg/L (enhanced bio-P) |
| Footprint | Smallest, up to 60% less than activated sludge | Compact, up to 60% less tank volume | One tank for all steps |
| Energy | Highest (membrane air scouring) | 0.3–0.8 kWh/m³ | Moderate, DO-controlled |
| Variable loads | Needs buffering and fine screening | Very robust | Very well suited |
| Typical capacity | 5–5,000 m³/day | Sized on BOD and NH₄-N loads | 50–10,000 m³/day |
| Typical use | Water reuse, limited space, strict limits | Robust industrial treatment, plant upgrades | Variable flows, smaller communities |
When each process is the best choice
Choose MBR when
- the treated water is to be reused, for example for irrigation or toilet flushing;
- space is tight, as at hotels, resorts, industrial sites or decentralised communities;
- discharge limits for suspended solids or bacteria are strict.
Choose MBBR when
- an existing activated sludge plant is overloaded and needs more capacity without new tanks;
- high-strength industrial effluent with fluctuating loads has to be treated;
- robust, low-maintenance operation is a priority.
Choose SBR when
- flows vary strongly or arrive intermittently, as on industrial estates, at food and drink plants or in small communities;
- nitrogen and phosphorus removal is needed in a single tank;
- existing tanks or lagoons can be converted.
Design data needed for a proposal
The more of the following information you can provide, the more accurate the design and proposal:
- average and peak daily flow;
- type and origin of the wastewater (domestic, food and drink, chemical, mixed);
- influent BOD, COD, TSS, nitrogen and phosphorus concentrations;
- temperature and pH range, plus fats, oils and other problem substances;
- the discharge limits or reuse standard that must be met;
- available site area, existing tanks or lagoons, indoor or outdoor installation;
- for retrofits, the dimensions and current loading of the existing tanks.
Typical mistakes when choosing a package plant
- Sizing on average flow only. Peak flows and load peaks determine membrane area, cycle times and aeration capacity.
- Insufficient pre-treatment for MBR. Without fine screening, hair and fibres damage the membranes and shorten their life.
- Ignoring fats and oils. Greasy wastewater needs pre-treatment and, where relevant, polyurethane diffuser membranes instead of EPDM.
- Forgetting MBBR solids separation. The carriers retain biomass, but the effluent still needs a clarifier or comparable separation step.
- Underestimating cold wastewater. Nitrification slows down at low temperatures, so the design must be based on the coldest relevant conditions.
Frequently asked questions
What is the difference between MBR and MBBR?
An MBR keeps suspended activated sludge in the tank and separates the treated water with 0.04 µm membranes, which gives reuse-quality effluent with TSS below 1 mg/L. An MBBR grows the biomass on moving plastic carriers, which makes it compact and robust, but it needs a separate clarifier or another separation step.
Is SBR or MBR better for a small community?
If the effluent is simply discharged and flows fluctuate, an SBR is often the simpler solution, as it handles variable flows well and treats nitrogen and phosphorus in one tank. If the water is to be reused or space is very limited, a packaged MBR from 5 m³/day is the better fit.
Can a packaged MBR treat industrial wastewater?
Yes, provided the pre-treatment is suitable. Fine screening is essential, and oils, fats or toxic substances must be reduced before the biological stage.
Can an existing plant be upgraded instead of replaced?
Often, yes. Adding biofilm carriers converts existing tanks into an MBBR and can increase biological capacity without new tankage. Alternatively, submerged membrane modules can replace the secondary clarifier and raise effluent quality to MBR level.
Every wastewater is different, and the right process depends on your flows, loads and discharge requirements. Send us your wastewater data via our contact page and our engineers will prepare a proposal for a suitable MBR, MBBR or SBR package plant within 48 hours.