What a Containerized MBR STP Is and Why It Fits San Diego Sites
A containerized MBR STP is a membrane bioreactor sewage treatment plant built inside a 20' or 40' high-cube ISO container, delivered factory-assembled, and lifted onto a prepared pad. Pure Aqua (S4) ships the MBR-C in 20' or 40' HC containers with insulated walls, a 1.5 mm drum screen on the inlet, fine-bubble diffusers in the aeration tank, and submerged hollow-fiber PVDF ultrafiltration modules. MENA-Water (S2/S5) and SIGMADAF (S1) describe the same architecture: a complete biological-plus-membrane system, pre-engineered and tested before shipping, so a San Diego site crew can complete hookup in days rather than months. The end result is a containerized MBR membrane bioreactor system that behaves like a packaged utility asset rather than a poured-concrete plant.
Inside the container, the MBR is an aerobic activated-sludge reactor where submerged ultrafiltration membranes replace the secondary clarifier, sand filter, and most of the tertiary polishing (SIGMADAF, S1). SIGMADAF (S1) reports biomass concentrations of 6,000–12,000 mg/L — roughly three to five times a conventional activated-sludge tank — because the membranes retain solids that a clarifier would lose. The membranes cited by Pure Aqua (S4) have a nominal pore size of 0.04 µm, which strips bacteria and most viruses in a single step. For a San Diego project, this effluent quality is generally sufficient for sewer discharge to the City of San Diego or for further polishing to California Title 22 water-reuse standards, depending on the disposal path you choose.
The MBR is not a complete pretreatment plant. SIGMADAF (S1) is explicit that fats, oils, hair, and grit must not enter the reactor or the membranes foul, so a 1.5 mm drum screen (Pure Aqua, S4) upstream is mandatory regardless of whether the source is a residential subdivision, a seasonal camp, or a worker colony. Plan for that screen and the pad it sits on as part of the containerized MBR package plant, not as an afterthought.
Step 1 — Convert Occupancy Into Design Flow (gpd and m³/day)
The sizing workflow starts with two numbers: peak population and a per-capita flow rate. Pure Aqua's MBR-C population-equivalent table is built on 50 gallons per person per day (Pure Aqua, S4), and that figure is the design basis used to map container size to occupancy. For a San Diego residential or camp project, take peak occupancy — the maximum number of people on site on the busiest day — and multiply by 50 gpd to get the baseline daily flow before any peaking adjustment.
Residential and camp occupancies behave differently. A year-round residential community runs close to its average every day, so a 1.0–1.2× peaking factor is usually enough to cover morning and evening overlap. A camp — whether summer camp, migrant housing, or a seasonal worker colony — runs at low base flow in winter and surges during check-in, communal meals, shower blocks, and laundry cycles, so a 1.4–1.8× peaking factor is the right starting band. Pure Aqua (S4) does not publish a camp-specific factor; the 1.4–1.8× band is engineering practice for transient high-density occupancy and should be confirmed with the local reviewer.
The math is straightforward: design flow (gpd) = population × 50 gpd × peaking factor. To convert to cubic metres per day, divide by 264.2. Worked example: 200 campers × 50 gpd × 1.5 = 15,000 gpd ≈ 57 m³/day. San Diego's arid climate and indoor plumbing mean inflow is close to the design number — there is no stormwater dilution to lean on, so use the calculated value as the design flow rather than discounting it.
Step 2 — Check the Organic and Ammonia Load
Hydraulic capacity is only half of sizing. An MBR can move 57 m³/day of water through its membranes and still fail if the load on the biomass is wrong. For San Diego residential and camp projects, the design BOD and ammonia numbers must be confirmed with the local sewer agency or RWQCB, because camp and worker-colony kitchens, showers, and laundry can push organics well above typical domestic values.
MBRs tolerate high load better than conventional activated sludge because SIGMADAF (S1) cites 6,000–12,000 mg/L mixed-liquor suspended solids inside the reactor. That high biomass compresses the biological stage into a small footprint, but it only works if the food-to-microorganism ratio, solids retention time, and aeration are sized for the actual influent — not a generic municipal number. A supplier who quotes m³/day without asking for BOD, NH₃-N, and peak factor is quoting a pump, not a treatment plant.
When the disposal route is surface irrigation under Title 22, or when the City of San Diego's discharge limits trigger a nitrate cap, the biological stage needs an anoxic pre-chamber for nitrification–denitrification. SIGMADAF (S1) describes this configuration as a modified MBR system designed for high-nitrogen or nitrate-limited effluents. Ask any vendor whether their quoted container includes the anoxic zone, because adding it later means another tank, another blower, and a different container count.
Step 3 — Match Flow and Load to a Container Size
Containerized MBRs ship in two physical sizes: 20' high-cube and 40' high-cube ISO containers (Pure Aqua, S4). Everything else — tank count, membrane area, blower size — fits inside one of those two envelopes. MENA-Water (S2/S5) reports that more than 1,200 m³/day can be filtered in a single 40-ft ISO container at industrial scale, so any residential or camp flow in the typical 10–200 m³/day band will fit in one container, with the 20' HC covering the lower end and the 40' HC covering flows from roughly 50 m³/day upward.
The table below maps the design flow from Step 1 to a container size and the approximate population served at 50 gpd per capita, based on Pure Aqua's (S4) MBR-C sizing basis. Treat the values as a starting point for supplier discussion, not a guarantee — membrane area and blower sizing depend on the load inputs from Step 2.
| Design flow (m³/day) | Design flow (gpd) | Approx. population @ 50 gpd/capita (no peaking) | ISO container | Typical application |
|---|---|---|---|---|
| 10 | ~2,640 | ~50 | 20' HC | Small cabin cluster, single dorm |
| 25 | ~6,600 | ~130 | 20' HC | Small camp, worker colony |
| 50 | ~13,200 | ~260 | 40' HC | Residential community, mid-size camp |
| 100 | ~26,400 | ~530 | 40' HC | Larger camp, multi-building residential |
| 200 | ~52,800 | ~1,050 | 40' HC (single) or two 40' HC | Large camp or community |
Footprint and weight drive site planning, not container count. A 40' HC container with water in its internal tanks is heavy, and a fully loaded unit needs a level concrete pad, truck access for delivery, and crane clearance for the lift. Confirm those constraints against the San Diego parcel before the supplier engineers the skid.
Step 4 — Lock In Pre-Treatment, Post-Treatment, and Reuse Targets
Pre-treatment is not optional. Pure Aqua (S4) builds a drum screen with 1.5 mm perforation into the MBR-C inlet specifically to keep hair, lint, and suspended solids off the membrane surface, and SIGMADAF (S1) repeats the warning that fats, oils, and hair must not enter the reactor. For a camp with shared kitchens and laundry, add a rotary mechanical bar screen for MBR pre-treatment ahead of the container to catch the FOG and rag load that a drum screen alone will miss.
Post-treatment depends on the discharge path. If the goal is on-site irrigation under California Title 22, plan for a disinfection barrier downstream of the MBR — UV or chlorination — because the MBR effluent is near-reuse quality but Title 22 still requires a disinfection step. A UV sterilizer for Title 22 reuse polishing is the usual fit for small community and camp flows, sized to the permeate pump flow rate. If the goal is sewer discharge, confirm the City of San Diego's discharge limits for nitrogen and surfactants before selecting the configuration; nitrate limits typically force the anoxic pre-chamber option described by SIGMADAF (S1).
Sludge handling is the line item that gets dropped from early budgets. MBR waste sludge is low-volume — SIGMADAF (S1) notes that sludge generation is minimal and requires only occasional blowdowns — but it still has to go somewhere. Factor in a small sludge storage tank and a licensed hauler arrangement sized to the blowdown frequency your supplier quotes, and confirm the receiving facility will accept the waste classification.
Step 5 — Apply the San Diego Sizing Checklist
Before a container is ordered, four site-side items have to line up. First, electrical supply: the MBR-C standard is 460 V / 3 Ph / 60 Hz (Pure Aqua, S4). Most San Diego residential sites run single-phase 120/240 V service, so confirm whether SDG&E can deliver three-phase to the parcel or whether a step-up transformer is needed — that is a hidden cost and a long lead item. Second, ambient temperature: Pure Aqua (S4) designs for 20–30°C operating with a 20°C design point. Coastal San Diego sits in that band year-round; inland and mountain camp sites can drop below 20°C on winter nights, which reduces nitrification efficiency and should be discussed with the supplier before the aeration package is locked.
Third, site access and noise. Aeration blowers are the dominant noise source on a packaged MBR, so the setback from the nearest residence matters for both the City of San Diego permit and the camp operator's neighbor relations. Fourth, the regulatory lane. The City of San Diego Sewer Design Guide governs any connection to the municipal sewer; the San Diego RWQCB (Region 9) governs on-site reuse and discharge to surface or groundwater; local building and zoning apply regardless. Permit timelines on these items routinely exceed the equipment lead time, so start the regulatory path before the deposit goes down.
Step 6 — Validate With a Sizing Worksheet and a Supplier
A sizing worksheet is the deliverable that turns the math above into comparable quotes. The input side should list peak population, design flow in gpd and m³/day, influent BOD and NH₃-N, effluent target, site elevation, available electrical service, and the maximum container footprint the parcel will accept. The output side, which a reputable supplier must return in writing, should list container size and count, total membrane area, MLSS target, blower kW, permeate pump kW, expected daily waste-sludge volume, and chemical consumption for membrane maintenance.
Cross-check the quote against reference designs. SIGMADAF (S1) and MENA-Water (S2/S5) both publish package-plant references in the 1–1,000+ m³/day envelope, so a San Diego residential or camp project sits firmly inside the documented design space. For the same flow band, a single 20' or 40' HC container from a packaged-MBR supplier — paired with a PVDF flat-sheet MBR membrane module if redundancy is needed — is usually the lowest-risk path for a project at this scale. Once the worksheet and the supplier's output line up, the containerized MBR STP is ready to order.
Frequently Asked Questions
How many people can one containerized MBR serve?
At Pure Aqua's (S4) 50 gpd per capita design basis, a single 20' HC container covers roughly 50 people at no peaking, and a 40' HC container covers up to about 530 people at no peaking. MENA-Water (S2/S5)
Frequently Asked Questions
How many people can one containerized MBR serve in San Diego?
A standard 40-foot containerized Membrane Bioreactor (MBR) unit typically processes between 10,000 to 25,000 gallons per day (GPD). Based on the California plumbing code estimate of 25 to 50 gallons per person per day for camps, a single unit can serve a population ranging from 200 to 1,000 people depending on the influent biological load and peaking factors.
What is the typical lead time for a containerized MBR delivered to San Diego?
The typical lead time for a custom-fabricated containerized MBR system ranges from 20 to 32 weeks. This includes the design phase, procurement of specialized membrane modules, off-site assembly, and factory acceptance testing before shipping to the San Diego site.
Do I need a discharge permit to send containerized MBR effluent to the San Diego sewer?
Yes, you must obtain an Industrial Wastewater Discharge Permit from the City of San Diego Public Utilities Department. Even if the effluent meets high-quality standards, the city requires a permit to monitor flow rates, chemical constituents, and potential impacts on local collection system infrastructure.
Can a containerized MBR meet California Title 22 for on-site irrigation at a camp?
Yes, containerized MBR systems can be configured to meet California Code of Regulations Title 22 standards for disinfected tertiary recycled water. To achieve this, the system must include redundant membrane filtration, strict turbidity limits of less than 0.2 NTU, and validated ultraviolet (UV) or chlorine disinfection processes.
What is the most common reason a containerized MBR undersizes for a camp project?
The most common cause of undersizing is the failure to account for diurnal peak flow variations and high-strength influent characteristics typical of camps. Designers often use average daily flow calculations rather than peak hourly flows, leading to hydraulic overloading of the membrane tanks and insufficient biological retention time during high-occupancy weekends.