How the four-step sizing chain works for Alexandria projects
Sizing a containerized MBR STP for an Alexandria residential or camp project follows four steps. First, set the design population and select a per-capita flow (a 190 L/c/d baseline fits Egyptian residential ranges; lift to 200–250 L/c/d for camps with shared showers, kitchens, and laundry) to get Qavg. Second, convert to Qpeak using a peak factor of 2.0–2.5 for camps and 1.5–1.8 for steady residential. Third, match Qpeak against the standard container envelope — a 20 ft HC handles up to ~50 m³/day, a 40 ft HC covers 50–200 m³/day, with paralleling for higher flows. Fourth, layer Egypt-specific checks: specify 380V/3Ph/50Hz for the Egyptian grid, confirm 20–30°C ambient compatibility, and target EEAA Decree 44/2000 effluent limits before reuse is approved.
A containerized MBR is a pre-engineered membrane bioreactor inside a 20 ft or 40 ft high-cube container with a 0.04 µm submerged UF membrane (HydropureWater, S4; Pure Aqua, S4). The process train is fixed: feed passes a 1.5 mm drum screen, flows through an anoxic/aerobic biological stage, then through a submerged PVDF UF membrane tank before disinfection. For North Coast construction camps, Cairo-Alexandria desert road labour bases, and Borg El-Arab housing blocks, the unit arrives on a flatbed, drops onto a concrete pad, and needs only power and piped influent to start up — no reinforced basins, no long civil schedule (HydropureWater, S4).
The chain matters because membrane cassettes are flux-rate-limited, so the unit must be sized for Qpeak, not Qavg — otherwise transmembrane pressure rises and cleaning cycles shorten. The same four-step containerized MBR sizing method for African grid conditions is laid out in the HydropureWater Kinshasa guide, but every input here is rebound to Egyptian voltage, climate, and compliance. Walk the chain in order; skipping a step is the most common reason a quotation pack has to be reissued.
Step 1 — Set the design population and pick an Egyptian per-capita flow
The most common sizing mistake in Egyptian projects is under-counting occupants or copying a hotel per-capita value onto a labour camp. The design population is the primary input, and the per-capita flow is the multiplier that turns headcount into Qavg. Pure Aqua's stock baseline is 50 gpd, approximately 190 L per capita per day (HydropureWater, S4), and that figure is a starting point rather than a universal rule.
For a typical Alexandria residential development, where occupants are full-time and water fixtures are limited, per-capita flows of 130–180 L/c/d are more representative of Egyptian fixture norms (HydropureWater, S4). Labour camps on the North Coast and along the Cairo-Alexandria desert road, with shared showers, kitchen messes, and laundry facilities, typically sit at 200–250 L/c/d (HydropureWater, S4). Add 5–10% to headcount for visitors, guests, and shift-changeover surges, because a single morning wash block serving 300 workers in 90 minutes is a worst-case pattern that the next step must absorb (HydropureWater, S4).
Get the occupancy profile right before committing. Full-time residential is steady; seasonal construction peaks for 3–6 months; a shift-worker camp produces a sharp daytime peak that affects Qpeak. The only way to lock the per-capita number for an Alexandria site is an on-site water-use survey; do not commit before influent sampling across at least 2 weekdays and 1 weekend day, per the HydropureWater S4 methodology, applicable to Alexandria conditions. Without that survey, the per-capita value remains a placeholder and the rest of the sizing chain inherits its uncertainty.
Step 2 — Convert Qavg to Qpeak with a peak factor
A membrane bioreactor's flux is rate-limited, so the unit must be sized for peak hourly flow (Qpeak) rather than just Qavg. Apply a peak factor (PF) of 2.0–2.5 for camp occupancies and 1.5–1.8 for steady residential developments (HydropureWater, S4). The formula is Qpeak = Qavg × PF, then divide by 24 to get m³/h when Qavg is expressed in m³/day.
The factor matters because the membrane tank's equalization volume is finite. If the buffer is too small, influent surges push transmembrane pressure (TMP) up, shorten cleaning intervals, and risk compliance excursions during peak windows. Most containerized MBR skids include a small internal equalization tank sized for typical diurnal patterns; if the camp's peak profile is extreme — for example, a single morning wash block serving 300 workers in 90 minutes — specify external buffer storage of at least 4–6 hours of Qpeak (HydropureWater, S4). Internal equalization alone will not absorb that kind of surge.
A conservative engineer sizes for the worst observed 4-hour window, not the 24-hour average, and adds 20–30% spare capacity above Qpeak for population growth, seasonal load spikes, and future reuse upgrades (HydropureWater, S4). When evaluating a containerized MBR system for quotation, request the manufacturer's peak-factor curve and internal equalization volume so the spare-capacity assumption can be checked against the actual skid envelope rather than a generic datasheet.
Step 3 — Match Qpeak to the 20 ft or 40 ft container envelope
The standard envelope is fixed: a 20 ft HC unit handles up to ~50 m³/day; a 40 ft HC unit covers 50–200 m³/day; multiple containers can be paralleled for higher flows (HydropureWater, S4; Pure Aqua, S4). Translating Qpeak into a specific container size requires adding 20–30% spare capacity above Qpeak, then picking the smallest envelope that fits the resulting flow.
Worked example — 300-person North Coast construction camp. With the stock 190 L baseline, 300 × 190 L = 57,000 L/day = 57 m³/day Qavg. Lift the per-capita to 220 L for a camp with full showers and a canteen, and Qavg rises. Applying a camp peak factor of 2.2 to a 57 m³/day Qavg: Qpeak = 57 × 2.2 / 24 = 5.2 m³/h, which sits at the upper edge of a single 20 ft HC envelope with little spare capacity. The right call is to spec a 40 ft HC, or parallel two 20 ft units with one held as standby (HydropureWater, S4).
Worked example — 150-person New Borg El-Arab housing development at ~28 m³/day average. A single 20 ft HC unit with 20–30% spare capacity is the right call, and the second pad can stay plumbed but empty until occupancy climbs. For phased construction, the rule is to install a 20 ft unit now, plumb the second pad, and add the second 20 ft when occupancy hits 70% of design (HydropureWater, S4). The submerged membrane cassette inside either format can be expanded or replaced without replacing the container, so the scale-up is a cassette swap, not a crane lift.
| Population (at 190 L/c/d) | Container format | Approx. envelope | Spare-capacity note |
|---|---|---|---|
| Up to ~250 people | Single 20 ft HC | ≤ 50 m³/day Qavg | Hold 20–30% spare above Qpeak |
| ~250–500 people | 40 ft HC, or 2× 20 ft HC (one standby) | 50–100 m³/day Qavg | Parallel second unit at 70% occupancy |
| ~500–1,000 people | Multiple 40 ft HC paralleled | 100–200 m³/day Qavg | Reserve pad space at quotation stage |
| > 1,000 people | Modular parallel train (3+ units) | > 200 m³/day Qavg | Confirm crane access and pad geometry |
When requesting a quotation, ask the supplier to confirm the MBR cassette count and the internal equalization volume against the Qpeak value, not the Qavg, so the spare-capacity line in the table above reflects the actual delivered skid.
Step 4 — Egypt-specific site checks before you sign the PO
Four integration issues derail Egyptian projects before the first container is lifted: voltage, climate, compliance, and power resilience. Each one is catchable at quotation if the engineer asks the right question.
Power. Egypt's grid is 380V / 3Ph / 50Hz (Egyptian Electricity Holding Co. standard), which is distinct from the 220–240V / 50Hz Senegalese grid cited in the HydropureWater S4 methodology and the 460V / 3Ph / 60Hz stock Pure Aqua MBR-C build (HydropureWater, S4). Order a voltage-matched build or specify a step-down transformer at quotation; do not assume the stock spec will land on Egyptian terminals.
Climate. Alexandria summer ambient sits inside the 20–30°C operating band, so no HVAC is needed, but verify peak summer wastewater temperature during the site survey and check humidity at the pad location for control-panel derating. Coastal humidity in Alexandria and on the North Coast can push panel cabinets close to their derating curve in July and August.
Compliance. Confirm the receiving environment — Lake Mariout discharge, on-site irrigation, or municipal sewer — and target EEAA Law 48/1982 and Decree 44/2000 effluent limits before reuse is approved. On-site irrigation typically needs additional disinfection and possibly nutrient polishing beyond the stock MBR envelope, so build that step into the spec sheet rather than retrofitting it later. For a comparable compliance pathway on a different grid, see the MBR compliance pathway for reuse applications.
Power resilience. A typical Alexandria site experiences 4–8 hours of grid interruption per week, per the HydropureWater S4 methodology calibrated to Egypt grid reliability, so size a genset or solar buffer; otherwise a membrane plant will trip on the first sustained outage. Screening: camp greywater can carry sand, hair, and plastics that overwhelm a 1.5 mm drum screen if upstream grit removal is skipped, so specify a PVDF flat sheet membrane cassette protected by a matched rotary bar screen for upstream grit removal.
Alexandria design envelope at a glance
The stock design envelope is 20–30°C operating temperature with a 20°C design point, BOD 200–400 mg/L, COD 400–800 mg/L, and TSS 200–350 mg/L (HydropureWater, S4) — all of which match typical Alexandria residential and camp sewage. Effluent typically meets near-reuse quality (BOD < 5 mg/L, TSS < 1 mg/L per Pure Aqua's envelope, S4), which sits well below typical EEAA reuse limits for irrigation.
| Parameter | Stock containerized MBR envelope | Typical Alexandria residential / camp sewage |
|---|---|---|
| Operating temperature | 20–30°C (20°C design point) | Within band year-round |
| BOD influent | 200–400 mg/L | Low–moderate; canteen effluent may push higher |
| COD influent | 400–800 mg/L | Low–moderate; kitchen waste lifts COD |
| TSS influent | 200–350 mg/L | Low–moderate; sand from camp greywater |
| Pre-screen | 1.5 mm drum screen required | Mandatory for rags, sand, plastics |
| Stock power | 460V / 3Ph / 60Hz (stock build) | 380V / 3Ph / 50Hz (Egypt grid) — order matched |
| Effluent BOD | < 5 mg/L | Complies with EEAA Decree 44/2000 irrigation reuse |
| Effluent TSS | < 1 mg/L | Complies with EEAA Decree 44/2000 irrigation reuse |
For projects that include upstream grit removal, a rotary bar screen for upstream grit removal sized to the design flow keeps the 1.5 mm drum screen from blinding during the camp wash-block peak. Confirm screen aperture and spacing against the supplier's data sheet, since the screen is the first line of defence for the membrane cassette.
Selecting the right container format for your population
Use the population-to-container selector below to map indicative headcount (at 190 L/c/d) directly to a 20 ft HC, 40 ft HC, or paralleled configuration, with footprint and pad notes (HydropureWater, S4). All values are recalibrated to Egypt metric pads and the standard 150 mm RC flat concrete pad typical of the HydropureWater S4 reference build.
| Indicative population (at 190 L/c/d) | Container format | Footprint (L × W) | Pad note |
|---|---|---|---|
| Up to ~250 people | Single 20 ft HC | ~6.0 m × 2.4 m | Standard flatbed; tight sites OK |
| ~250–500 people | 40 ft HC, or 2× 20 ft HC | ~12.0 m × 2.4 m | Reserve space for parallel second 20 ft |
| ~500–1,000 people | Multiple 40 ft HC paralleled | ~12.0 m × 2.4 m per unit | Standard flatbed; longer clear approach |
| > 1,000 people | Modular parallel train | Sum of unit footprints + 1 m walkways | Allow crane access for lift-on/lift-off |
Reserve space for a parallel second 20 ft unit on every pad, even when the quotation only ships one, because adding the second unit at 70% occupancy is cheaper than retrofitting a pad later. The 150 mm RC pad is typical, but verify against the supplier's point-load data for the cassette skids inside the container, and confirm crane access for the lift-on/lift-off cycle before signing the PO on a containerized MBR system. For hospitality-scale packaged selection on a similar climate, see the packaged MBR selection for hospitality projects guide.
Frequently asked questions
What voltage specification do I need for an Alexandria containerized MBR?
Egypt's grid is 380V / 3Ph / 50Hz, while most stock containerized MBR skids ship at 460V / 3Ph / 60Hz. The buyer must request a voltage-matched build or confirm that a step-down transformer is included in the supplier's scope, and ask for the transformer kVA rating and impedance data so the genset and protection settings downstream can be coordinated.
Which EEAA permits apply to a containerized MBR in Alexandria?
Discharge and reuse are governed by EEAA Law 48/1982 and Decree 44/2000. The buyer must request the supplier's effluent compliance sheet showing BOD, COD, TSS, and faecal coliform against Decree 44/2000 limits, and confirm with the local EEAA branch whether the receiving environment — Lake Mariout, on-site irrigation, or municipal sewer — triggers additional disinfection or nutrient polishing before approval.
What is the typical lead time for a 20 ft or 40 ft HC MBR to an Alexandria site?
Lead time is project-specific and depends on the voltage-matched build, cassette configuration, and screen selection. The buyer must request a written delivery schedule from the supplier that includes the voltage-matched variant, the 1.5 mm drum screen, and any compliance-monitoring panel, and confirm whether the quoted Incoterm covers Alexandria port handling and inland transport to the North Coast, Cairo-Alexandria desert road, or Borg El-Arab pad.
Can a 20 ft HC unit be paralleled with a 40 ft HC unit on the same project?
Yes, but the hydraulic profile and PLC control must be matched. The buyer must request confirmation from the supplier that both units share a common control philosophy, equalization strategy, and alarm map, and that the influent manifold and effluent header are sized for the combined Qpeak rather than the individual unit envelope.
