Choose MBR when you need the best effluent quality for water reuse or strict discharge limits in the smallest footprint; MBBR when you want robust, low-maintenance treatment that tolerates fluctuating loads; and A2O when you need biological nitrogen and phosphorus removal at the lowest operating cost and have space for a clarifier. Many package plants combine these, for example A2O with MBBR media or A2O followed by MBR.
Which package sewage treatment process is right for you?
For most decentralized projects, the choice comes down to three biological processes. MBR (membrane bioreactor) gives reuse-quality effluent in the smallest footprint but costs more to run and maintain. MBBR (moving bed biofilm reactor) is robust and simple, handling variable loads well. A2O (anaerobic–anoxic–oxic) is the classic, low-energy route to nitrogen and phosphorus removal but needs a secondary clarifier and more space.
This guide explains how each process works, compares them in one table, and matches them to villages, hotels, hospitals and factories. For equipment options, see our package sewage treatment plants.
What is a package sewage treatment plant?
A package (or integrated) sewage treatment plant is a factory-built system that combines several treatment stages, typically screening, equalization, biological treatment, solids separation and disinfection, in one or more steel, FRP or containerized tanks. It is delivered ready for connection, which shortens site construction compared with poured-in-place concrete plants.
Package plants commonly serve populations from a few dozen to several thousand people, or flows from a few cubic meters to a few thousand cubic meters per day. Larger capacities are reached by installing several modules in parallel.
How do MBR, MBBR and A2O work?
A2O (anaerobic–anoxic–oxic)
A2O is an activated sludge process with three zones in sequence. In the anaerobic zone, phosphorus-accumulating bacteria release phosphorus and store organic carbon. In the anoxic zone, bacteria use nitrate recycled from the aerobic zone to oxidize organic matter, converting nitrate to nitrogen gas (denitrification). In the oxic (aerobic) zone, air is supplied so bacteria oxidize organic matter and convert ammonia to nitrate (nitrification), while phosphorus-accumulating bacteria take up excess phosphorus. A secondary clarifier then separates the sludge, which is partly returned and partly wasted.
MBBR (moving bed biofilm reactor)
MBBR tanks are partly filled with small plastic carriers, typically polyethylene or polypropylene, that provide a large protected surface area for biofilm. Aeration or mixers keep the carriers moving, and a sieve at the outlet keeps them in the tank. Because biomass is attached to the media, MBBR tolerates shock loads and does not need sludge return. It still needs downstream solids separation, such as a settler or lamella clarifier.
MBR (membrane bioreactor)
MBR combines activated sludge with microfiltration or ultrafiltration membranes, usually submerged hollow-fiber or flat-sheet modules. The membranes replace the secondary clarifier, so the process can run at much higher mixed liquor concentrations, typically around 8,000–12,000 mg/L compared with roughly 2,000–4,000 mg/L in conventional activated sludge. Effluent passes through the membrane pores, so suspended solids are almost completely removed.
How do MBR, MBBR and A2O compare?
The table summarizes typical characteristics. Actual performance depends on influent quality, design loading and operation.
| Factor | A2O | MBBR | MBR |
|---|---|---|---|
| Effluent suspended solids | Depends on clarifier; typically good | Depends on settler; typically good | Very low; near zero |
| Nitrogen removal | Good (designed for it) | Good with anoxic stage | Very good with anoxic stage |
| Biological phosphorus removal | Good | Limited; chemical dosing often added | Good with anaerobic zone or chemical dosing |
| Suitability for direct water reuse | Needs tertiary filtration | Needs tertiary filtration | Yes, with disinfection |
| Footprint | Largest | Medium | Smallest |
| Energy use | Lowest | Low to moderate | Highest (membrane scouring air) |
| Tolerance to load swings | Moderate | High | Moderate to high |
| Sludge production | Moderate | Moderate | Lower (long sludge age) |
| Operator skill required | Moderate | Low | Higher |
| Key maintenance items | Blowers, sludge return, clarifier | Blowers, media sieves | Membrane cleaning and eventual replacement, blowers, permeate pumps |
| Relative capital cost | Low | Low to medium | Highest |
Hybrid configurations
Process labels overlap in practice. Common package plant designs include A2O with MBBR carriers in the aerobic zone (often called A2O-MBBR) to boost nitrification in a smaller tank, and A/O or A2O followed by MBR for reuse-quality water. When you compare quotes, ask for the full process train, not just the headline name.
Which process suits each application?
Villages and rural communities
Village systems face strongly varying flows (morning and evening peaks, seasonal population) and often have no full-time operator. MBBR or A2O-MBBR is usually the best fit because it tolerates load swings and needs little routine attention. An adequately sized equalization tank and simple remote alarms matter as much as the biological process. MBR is chosen where effluent must be reused for irrigation or discharged to a sensitive water body.
Hotels and resorts
Hotels often have limited space, strict aesthetic and odor requirements, and an interest in reusing treated water for landscaping or toilet flushing. MBR is the common choice for this reason. Resorts with seasonal occupancy need a plant that can be turned down without losing biomass; modular trains or a generous equalization tank help. Kitchen wastewater should pass through a grease trap first.
Hospitals and clinics
Hospital wastewater is similar to domestic sewage but carries higher pathogen loads and may contain pharmaceuticals and disinfectant residues. Regulators typically require effective disinfection with specified contact time and residual. MBR provides excellent solids removal, which improves disinfection reliability, while A2O or MBBR followed by good filtration is also used. Pair the plant with an on-site sodium hypochlorite generator to avoid storing large volumes of chemical.
Factories and industrial parks
A package plant is ideal for the domestic sewage from staff toilets, showers and canteens. Industrial process wastewater is different: it may contain oil, high COD, metals or extreme pH. Treat it separately or pretreat it, for example with dissolved air flotation for oily or high-solids streams, before blending with sanitary flow. MBBR is often preferred for its resilience to occasional load spikes.
How do you choose step by step?
- Define the design flow. Establish average daily flow, peak hourly flow and future expansion. For populations, use a local per-capita figure rather than a generic one.
- Characterize the influent. Typical parameters are BOD5, COD, TSS, ammonia, total nitrogen, total phosphorus, oil and grease, pH and temperature.
- State the discharge or reuse standard. Write the exact effluent limits that apply, including nitrogen, phosphorus and coliform limits if any.
- Assess the site. Note available area, ground conditions, whether tanks will be buried or above ground, climate (cold water slows nitrification) and power supply.
- Consider operation and maintenance. Be honest about operator availability and access to chemicals and spare parts.
- Compare life-cycle cost. Include energy, chemicals, sludge disposal, membrane replacement (for MBR) and labor over at least 10 years.
- Plan sludge handling. Even small plants produce waste sludge; decide whether it will be tankered away or dewatered on site with a compact sludge dewatering machine.
What maintenance does each process need?
- A2O: Check blower operation, dissolved oxygen, internal and sludge recycle rates, and clarifier sludge blanket. Waste sludge regularly to hold the target sludge age.
- MBBR: Inspect outlet sieves for blockage, verify carriers are moving evenly, and maintain blowers and diffusers. Media typically lasts many years.
- MBR: Monitor transmembrane pressure and permeability, carry out routine maintenance cleans and periodic recovery cleans with chemicals such as sodium hypochlorite and citric acid as specified by the membrane supplier, and keep fine screening (often 1–3 mm) in good condition to protect the membranes. Membranes have a finite life and should be budgeted for replacement.
Should the plant be buried, above ground or containerized?
Package plants come in several physical formats. Buried tanks, often FRP or coated carbon steel, save space and keep the plant out of sight, which suits hotels, villages and residential developments; they need correct backfill, anchoring against groundwater uplift and safe access to manholes. Above-ground steel tanks are easier to inspect and maintain and suit factories and industrial parks. Containerized plants place the treatment process inside or around standard shipping containers, which simplifies transport and makes them easy to relocate for construction camps or temporary sites.
Common mistakes when buying a package plant
- Sizing on average flow without allowing for peak flow and equalization.
- Specifying "MBR" or "MBBR" without stating the required effluent quality.
- Skipping fine screening ahead of an MBR, which shortens membrane life.
- Sending untreated industrial wastewater into a domestic sewage plant.
- Forgetting disinfection, sludge handling and odor control in the scope.
Get a package plant recommendation
Send your design flow, influent data, discharge or reuse standard, site conditions and power supply to [email protected], or reach us through our contact page. We will propose an MBR, MBBR, A2O or hybrid package plant sized for your project, with a clear process flow diagram and equipment list.
FAQ
Which package sewage plant gives the best effluent quality?
An MBR plant typically gives the best effluent because its membranes physically retain suspended solids and most bacteria. Effluent suspended solids are usually close to zero, which makes MBR the common choice for reuse in irrigation, toilet flushing or cooling.
Is MBBR the same as activated sludge?
No. In MBBR most of the biomass grows as a biofilm on plastic carriers that move freely in the tank, rather than as suspended floc. This makes it more tolerant of load swings and means it does not rely on returning sludge from a clarifier.
Can a package sewage plant treat industrial wastewater?
Package plants are designed for domestic-type sewage. Industrial process water with high oil, toxic compounds, extreme pH or very high COD usually needs pretreatment, such as equalization, pH correction or flotation, before it enters a biological package plant.
What does a hospital sewage plant need beyond normal treatment?
Hospital plants need reliable disinfection, typically with sodium hypochlorite, and good solids separation so the disinfectant works effectively. Local regulations often specify contact time and residual chlorine.
