What "Sizing" a Containerized MBR STP Really Means in São Paulo
Sizing a containerized membrane bioreactor (MBR) sewage treatment plant (STP) is not the same as picking the smallest 20-ft box on a price list. For a São Paulo residential condominium, worker camp, or hospitality site, sizing is the combined act of setting three linked outputs: the average daily flow in m³/day, the peak hydraulic load in m³/h that the feed pump and membrane tank must absorb, and the physical envelope — one 20-ft high-cube (HC) ISO container, one 40-ft HC, or a buried alternative.
Manufacturer reference points anchor the math. Pure Aqua publishes a sizing table based on "approximately 50 gpd per capita," which is the per-person daily allowance a São Paulo engineer can use as a first-pass bracket before refining with local data. The footprint side is set by MENA-Water, whose package plants "are standardized, available in different sizes" and can filter "more than 1,200 m³/day in one 40-feet ISO container," with the inside tanks in stainless steel. That envelope frames the entire calculation: any small residential or camp project in São Paulo state will land well below 1,200 m³/day, which means a single 20-ft or 40-ft HC unit is the realistic ceiling.
Containerized MBR is attractive in São Paulo because the factory pre-engineering, plug-and-play transport, and compact footprint remove most of the civil works a buried activated-sludge plant requires on a tight urban or resort lot. The local regulatory lens, however, is unavoidable. Effluent quality must satisfy CONAMA Resolution 430/2011, and any discharge to the public sewer or water-reuse application must also satisfy SABESP and CETESB standards. Confirm the exact BOD, COD, TSS, total nitrogen, and E. coli limits with the local authority before locking the specification.
Step 1 — Estimate Population and Per-Capita Flow
The first input in any MBR sizing methodology is the number of people the plant will serve, broken into the user groups that actually drive the load. For a São Paulo condominium, this is permanent residents and daytime visitors. For a worker camp in the construction or agribusiness sector, it is the on-site labour force plus catering and laundry staff. For a hospitality site, it is guests, plus housekeeping and restaurant load. Each group has a different occupancy schedule, and those schedules matter because the STP has to handle the worst day, not the average day.
Apply the 50 gpd per capita figure as a manufacturer-published order-of-magnitude benchmark, not as a final number. Pure Aqua's MBR-C sizing table uses this 50 gpd value to convert population into approximate flow. A São Paulo engineer should still request a per-capita flow from the local water utility, from the SABESP design manual, or from the relevant NBR 9649/1986 guidance for the specific project type, because Brazilian residential and camp projects often carry a lower per-capita water allowance than the U.S. benchmark the manufacturer uses. When the local number is not yet available, treat the 50 gpd value as the upper end of the bracket.
Convert the resulting gallons per day to m³/day so the figure can be compared directly with container flow ratings. The IDA Water Security Handbook (2019) gives the conversion explicitly: 1 m³ = 264.2 US gallons, or 1,000 litres. So a 200-person camp at 50 gpd per capita is roughly 10,000 gpd, or about 38 m³/day. The qualitative inputs a São Paulo engineer must request from the client before finalising this number are: weekly occupancy schedule, peak meal hours in the restaurant or cantina, laundry volume (kg/day or loads/day), and any on-site process water — vehicle wash, kitchen grease, pool backwash — that also discharges to the STP and must be added to the sanitary load.
Step 2 — Convert Average Daily Flow to Peak Hydraulic Load
Average daily flow is the number you can compare against a container's nameplate capacity, but it is not the number that sizes the pumps, the membrane tank, or the bioreactor volume. Peak hydraulic load is. The peak flow in a São Paulo residential or camp project arrives in two surges — early morning, when residents shower and toilets flush, and evening, when cooking, laundry, and bathing overlap — and a worker camp adds a third peak at the shift-change shower block.
Apply a peaking factor that reflects the user type. Residential developments typically use 2.0–2.5× the average; worker camps, where the whole shift washes at the same time, use 2.5–3.0×; event-driven hospitality sites (weekend resorts, harvest-season agribusiness camps) sit higher again. Multiply the m³/day figure by the appropriate factor and convert to m³/h by dividing by 24 to get the peak hourly throughput the containerized MBR must absorb without surge overflow at the equalization tank.
Two design checks follow. First, the feed-water pump and the 1.5 mm drum screen that Pure Aqua specifies as the pre-treatment for the MBR-C are the first hydraulic bottlenecks on a peak day; both must be rated for the peak m³/h, not the average. Second, the hydraulic retention time (HRT) in the bioreactor must stay above the minimum at peak flow. Too short an HRT washes out biomass and degrades effluent BOD and COD, which is exactly the failure mode that triggers a CONAMA 430 non-conformance. If the peak HRT falls below the design value, either the equalization tank must be enlarged, or a second container must be added in parallel.
Step 3 — Match Flow to a 20-ft or 40-ft High-Cube Container
The container selection step is where the sizing calculation becomes a physical decision. MENA-Water states that its MBR package plants are built so that "more than 1200 m³/day can be filtered in one 40-feet ISO container." That figure is the upper end of the envelope; the lower end is set by what a 20-ft HC can hold once the membrane tank, bioreactor, blower, and control panel are all packed inside the insulated, seaworthy container that manufacturers like Pure Aqua describe.
The table below maps population bands at the 50 gpd per capita benchmark to m³/day and to a recommended container size for a São Paulo residential or camp project.
| Population (at 50 gpd per capita) | Average daily flow | Recommended container | Site check |
|---|---|---|---|
| 50 people | ≈ 9.5 m³/day | Single 20-ft HC | Confirm feed pump rated for peak ≈ 1.0–1.2 m³/h |
| 100 people | ≈ 19 m³/day | Single 20-ft HC | Confirm peak HRT ≥ design HRT in bioreactor |
| 200 people | ≈ 38 m³/day | Single 20-ft HC or compact 40-ft HC | Confirm drum screen and pump rated for peak ≈ 4–5 m³/h |
| 500 people | ≈ 95 m³/day | Single 40-ft HC | Confirm truck access and crane pad for delivery |
| 1,000 people | ≈ 190 m³/day | Single 40-ft HC | Confirm blower noise setback from residential receptors |
Cross-check the container selection against site constraints before issuing a purchase order. Truck access for delivery, a level crane pad, available footprint, and the setback distance to the nearest residential receptor (because the blowers and the drum screen generate both noise and aerosol) are all real project inputs that can rule a container in or out. Pure Aqua notes that the company engineers and builds its systems in-house and that "all of our water treatment systems are pre-engineered using the latest CAD technology," which is the engineering basis for a one-off custom configuration around the same core modules. For an engineer sizing a São Paulo camp, that flexibility matters when the site geometry does not match a standard container footprint.
Step 4 — Confirm Membrane, Electrical and Environmental Fit
A correctly sized container still fails if the membrane, the electrical supply, and the local climate are not aligned. Pure Aqua's MBR-C uses "hollow fiber (HF) ultrafiltration (UF) membranes with nominal pore size of 0.04 µm," built as submerged membrane modules in TIPS PVDF material — the same configuration often paired with the DF-series PVDF flat sheet membrane module when the project needs a higher solids tolerance. The membrane's 0.04 µm pore size is what gives MENA-Water's MBR a 99.9999% reduction of virus and bacteria, which is the basis for any reuse claim the buyer wants to make to a São Paulo client for irrigation or toilet flushing.
The published operating envelope must be checked against São Paulo state conditions. Pure Aqua lists the operating temperature range as 68–86 °F (20–30 °C) continuous, with a design temperature of 68 °F (20 °C), and the electrical supply as 460 V / 3 ph / 60 Hz. São Paulo state typically meets the voltage requirement, but the climate check is the one that catches projects in the Serra da Mantiqueira and Campos do Jordão regions, where winter mornings can fall below the 20 °C lower bound. If the project site is in a cooler microclimate, the engineer must either specify a heating jacket on the bioreactor or accept a derated flow at low temperature.
The effluent check closes the sizing exercise. The discharge or reuse target must be confirmed against CONAMA 430/2011 and the local SABESP or CETESB standard — BOD, COD, TSS, total nitrogen, and E. coli. If the local standard constrains total nitrogen, an anoxic zone for denitrification must be included in the bioreactor; Pure Aqua's MBR-C already lists an anoxic zone as a standard option for NO3 removal. A pipeline UV sterilizer downstream of the membrane is the typical polishing step when the reuse target demands a tighter E. coli limit than the membrane alone can certify.
Containerized MBR vs Buried A/O Package: Which Suits a São Paulo Camp?
The real choice a São Paulo camp or condominium developer faces is not container versus no container — it is containerized MBR versus a buried A/O package plant. The containerized option is an integrated MBR membrane bioreactor system with the membranes, blowers, and control panel pre-assembled inside a 20-ft or 40-ft HC ISO frame. The buried alternative is a WSZ-style underground integrated sewage treatment plant, where the aeration, settling, and disinfection stages sit below grade and only the control kiosk is visible.
| Criterion | Containerized MBR (20-ft or 40-ft HC) | Buried A/O package (WSZ-style) |
|---|---|---|
| Footprint | One container envelope, surface-mounted | Below grade, only kiosk visible |
| Visual impact | Visible enclosure; can be screened with landscaping | Effectively invisible once buried |
| Transport & installation | Plug-and-play, factory-tested, one crane lift | Multiple tank sections, on-site assembly, longer install |
| Installation time | Days once the pad is ready | Weeks for excavation, tank placement, backfill |
| Effluent quality & reuse | Reuse-grade, suitable for irrigation and toilet flush | Discharge-grade unless tertiary treatment is added |
| Expandability | Add a second container in parallel | Add a second buried train, with civil works |
| Decision rule | ||
| Temporary, remote, or reuse-quality site | Choose containerized MBR | — |
| Permanent, dense residential, visual sensitivity | — | Choose buried A/O package (WSZ underground integrated sewage treatment plant) |
| Large camp with high peak-to-average ratio | Containerized MBR + small buried equalization tank | — |
The decision rule is straightforward. Choose a containerized MBR when the site is temporary, remote, or needs reuse-quality water; the factory pre-engineering, transport speed, and 99.9999% pathogen reduction justify the visible enclosure. Choose a buried A/O package when the STP must be invisible and the site is permanent. For larger camp projects where the peak-to-average ratio stresses a single container, the hybrid — a small buried equalization tank feeding a containerized MBR — gives both peak buffering and a small above-grade footprint.
Frequently Asked Questions
What is the fastest way to size a containerized MBR for a 200-person camp in São Paulo?
Start with 200 people × 50 gpd per capita = 10,000 gpd, or about 38 m³/day (Pure Aqua benchmark). Multiply by a worker-camp peaking factor of 2.5–3.0 to get ≈ 4–5 m³/h peak. A single 20-ft HC container will hold that flow, but the engineer must confirm the feed pump, drum screen, and bioreactor HRT are rated for the peak — and that the site climate sits inside the 20–30 °C operating window.
How much does a containerized MBR STP cost in São Paulo, and what is the lead time?
The research sources do not publish a São Paulo-specific price or delivery window. The engineer must request a project-specific quotation that includes the container size, membrane area, blower redundancy, and any denitrification or UV polishing required by the local CETESB or SABESP standard. Lead time is driven by container fabrication, membrane module availability, and sea-freight scheduling to the Port of Santos — request the manufacturer's current build slot and shipping terms in writing before signing.
Which Brazilian discharge standard applies to a containerized MBR in São Paulo state?
CONAMA Resolution 430/2011 sets the national effluent quality framework, and SABESP and CETESB add local discharge and reuse requirements. The engineer must request the exact BOD, COD, TSS, total nitrogen, and E. coli limits from CETESB (or SABESP, for projects discharging to the public sewer) before specifying the membrane area or the polishing step, because those limits determine whether a denitrification zone or a UV unit must be added to the standard MBR-C configuration.
How do I verify a containerized MBR supplier before placing the order?
Request factory test certificates for the membrane modules, the documented operating envelope (20–30 °C, 460 V / 3 ph / 60 Hz), and a reference list of operating containerized MBR plants in climates comparable to São Paulo. Confirm the supplier's local representative can commission the unit, train the operator, and supply spare membranes within the lead time the project allows — and cross-check the sizing methodology against the steps in this guide before signing.
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