Aquatic Solutions manufactures Johkasou FRP packaged STP plants — compact, factory-built sewage treatment systems based on Japanese Johkasou technology housed in corrosion-proof FRP (fibreglass reinforced plastic) tanks. Each unit integrates primary settling, anaerobic-aerobic biological treatment, clarification and tertiary treatment (pressure sand filtration, activated carbon adsorption and UV/chlorine disinfection) in a single plug-and-play module. The treated water meets CPCB norms for discharge and, after tertiary polishing, is suitable for reuse in flushing, gardening, cooling tower make-up and vehicle washing — cutting a building's freshwater demand by up to 40%.
Johkasou technology originated in Japan, where it is governed by the Johkasou Law and JIS standards and has been installed at more than five million sites for decentralised sewage treatment. Aquatic Solutions adapts this proven technology for Indian conditions — manufacturing Johkasou-type FRP packaged STPs at its Mumbai facility for apartments, villas, commercial buildings, resorts, hospitals, schools and small industrial townships. The result is a sewage treatment plant that installs in days instead of months, needs no masonry civil work, resists corrosion for decades and delivers tertiary-grade treated water ready for reuse.
What Is a Johkasou FRP Packaged STP Plant?
Johkasou (浄化槽) is Japanese for 'purification tank' — a compact, prefabricated sewage treatment unit that treats sewage at the point of generation rather than at a centralised plant. The technology has been refined over decades in Japan, where strict JIS (Japanese Industrial Standards) certification governs its performance, and modern Johkasou units achieve BOD removal efficiencies above 90%.
- Factory-built in FRP — the entire treatment train (anaerobic chamber, aerobic/contact aeration chamber, settling chamber, disinfection) is pre-assembled inside a single moulded fibreglass tank
- Plug-and-play installation — delivered to site finished, set on a prepared base, connected to inlet/outlet and power, and commissioned within days
- No masonry civil work — unlike conventional RCC STPs, there is no excavation-heavy construction, curing time or waterproofing risk
- Silent, odour-controlled operation — enclosed aerobic process with blower-based aeration; suitable for installation inside building basements or landscaped areas
- Minimal operator skill — automated control panel with blower interlocks; routine maintenance is desludging every 6–12 months
Why FRP Construction Outperforms RCC and MS
The tank material determines how long a packaged STP lasts and how much it costs to maintain. Aquatic Solutions builds its Johkasou packaged STPs in FRP (fibreglass reinforced plastic) because it solves the failure modes that plague other materials.
| Aspect | FRP (Johkasou) | RCC | MS |
|---|---|---|---|
| Corrosion resistance | Immune — FRP is inert to sewage, H2S and soil chemicals; no rusting or spalling | Sulphate attack, rebar corrosion, leakage through cracked concrete | Rusts rapidly in sewage environment; needs continuous painting and lining |
| Weight and transport | Lightweight — transportable by small truck, installable in basements and tight sites | Cast in situ; heavy excavation and shuttering required | Heavy; crane needed for handling |
| Installation time | 2–5 days on site | 4–12 weeks including curing | 2–4 weeks |
| Service life | 25+ years with no surface treatment | Waterproofing fails in 10–15 years; repairs are costly | 10–15 years with coatings |
| Leak-proofing | Seamless moulded shell — zero leakage, zero groundwater contamination risk | Depends on construction quality; leakage is common | Weld seams are weak points |
| Aesthetics and placement | Can be buried, placed on terraces or in basements; blends into landscaping | Permanent structure; consumes footprint | Exposed industrial appearance |
How the Aquatic Solutions Johkasou FRP STP Works
Inside one FRP shell, sewage passes through five engineered treatment zones. The process follows the Japanese Johkasou configuration — anaerobic treatment followed by contact aeration — which delivers high BOD removal with very low power consumption.
1. Screen & Grit Chamber
Raw sewage enters through an inlet screen that traps rags, plastics and coarse solids. Grit settles at the base and is removed during periodic maintenance.
2. Anaerobic Filter Chamber
Screened sewage flows through submerged filter media where anaerobic micro-organisms break down 40–60% of the organic load without aeration. This pre-treatment slashes the oxygen demand on the downstream aerobic stage, cutting blower power consumption.
3. Contact Aeration Chamber
Fine-bubble diffusers supply oxygen to biofilm carriers, where aerobic bacteria consume the remaining BOD and oxidise ammonia. The biofilm structure makes the process resilient to flow swings — important for buildings with variable occupancy.
4. Sedimentation & Sludge Return
Treated water enters a settling cone where biological solids separate out. A sludge-return loop recycles settled solids back to the anaerobic chamber to maintain biomass, while excess sludge accumulates for periodic desludging.
5. Chlorine Contact / Disinfection Chamber
Clarified water passes through a chlorine contact chamber (or UV disinfection, optional) that destroys pathogens before the effluent leaves the unit — safe for discharge or onward tertiary treatment.
Tertiary Treatment: From 'Discharge-Grade' to 'Reuse-Grade' Water
Secondary-treated sewage meets CPCB discharge norms, but reuse for flushing and gardening demands lower suspended solids, turbidity and pathogen counts. Aquatic Solutions offers a skid-mounted tertiary treatment package that polishes the Johkasou unit's secondary effluent to reuse-grade quality.
Pressure Sand Filter (PSF)
Removes residual suspended solids and floc down to 10–20 micron level, protecting downstream equipment and reducing turbidity to under 5 NTU.
Activated Carbon Filter (ACF)
Adsorbs dissolved organics, colour, odour and residual detergent traces — the difference between water that looks treated and water that looks and smells clean.
UV Disinfection or Chlorination
UV lamps deliver a pathogen kill without residual chemicals — ideal for reuse where skin contact is possible (gardening, vehicle washing). Chlorine dosing provides residual protection in storage and distribution lines.
Optional MBR Upgrade
For projects targeting the highest reuse standards, an MBR (membrane bioreactor) module replaces the settling step — delivering turbidity under 1 NTU and a complete pathogen barrier, with water ready for cooling tower make-up after a polishing RO.
Treated Water Storage & Distribution
A dedicated treated-water tank with dual-pump hydro-pneumatic system feeds the reuse network — separate plumbing (marked purple/ISI piping) for flushing lines and irrigation points.
Reuse of Treated Water: Applications and Savings
Every litre of treated water reused is a litre of municipal or tanker water saved — and a litre that does not need to be paid for twice. For a typical residential project, flushing and landscaping account for 30–40% of total water demand, and the Johkasou STP's tertiary output covers that entire share.
| Reuse Application | Water Quality Required | Notes |
|---|---|---|
| Toilet flushing | BOD < 10 mg/L, turbidity < 5 NTU, faecal coliform nil | Largest reuse application — 25–35% of building water demand |
| Landscape irrigation and gardening | BOD < 30 mg/L, pathogen-safe (UV treated) | Drip and sprinkler irrigation for gardens, lawns, plantations |
| Cooling tower make-up | Low TDS and turbidity; MBR + RO polishing recommended | Significant savings for commercial buildings and hotels |
| Vehicle washing and floor washing | BOD < 10 mg/L after ACF + UV | Common in residential societies, malls and service stations |
| Construction activities (dust suppression, curing) | Basic secondary quality adequate | Immediate offset of tanker water purchases during construction |
CPCB and most state Pollution Control Boards now mandate treated-water reuse for new residential and commercial projects — many municipal bye-laws require dual plumbing for flushing in buildings above a defined area. Aquatic Solutions supplies the tertiary package and dual-plumbing advisory as part of the Johkasou packaged STP scope.
Johkasou FRP STP Capacities and Footprint
| Capacity | Suitable For | Approx. Footprint |
|---|---|---|
| 5 KLD | Bungalow, villa, small clinic, holiday home | Approx. 2.5 m × 1.5 m |
| 10–20 KLD | Small apartment block, farmhouse, guest house | Approx. 3 m × 2 m |
| 30–50 KLD | Mid-size apartment complex, hotel, school | Approx. 5 m × 2.5 m or twin modules |
| 75–100 KLD | Large residential tower, hospital, commercial building | Twin or triple modules in parallel |
| 150–500 KLD | Townships, resorts, campuses, industrial canteen blocks | Multiple FRP modules on a common header |
Why Aquatic Solutions for Your Johkasou FRP Packaged STP
Aquatic Solutions designs, manufactures and commissions Johkasou-type FRP packaged STPs entirely in-house — from moulding the FRP shell to wiring the control panel and training your housekeeping team.
- Japanese-origin Johkasou process design adapted to Indian sewage characteristics and CPCB norms
- In-house FRP manufacturing — quality-controlled shells, no third-party tank dependency
- Integrated tertiary treatment (PSF + ACF + UV) and reuse plumbing advisory in one scope
- Capacities from 5 KLD to 500 KLD — single modules and parallel module trains
- Turnkey delivery: installation, commissioning, O&M training and annual maintenance contracts
- Service locations: Mumbai, Pune, Hyderabad, Bangalore, Chennai, Goa, Surat, Noida
Related Products and Pages
Frequently Asked Questions
What is a Johkasou FRP packaged STP plant?
A Johkasou FRP packaged STP is a compact, factory-built sewage treatment plant based on Japanese Johkasou ('purification tank') technology, manufactured in a fibreglass reinforced plastic (FRP) shell. It integrates screening, anaerobic filtration, contact aeration, sedimentation and disinfection inside a single tank, treating sewage at the point of generation without any civil construction. Aquatic Solutions manufactures these units in capacities from 5 KLD to 500 KLD for apartments, villas, commercial buildings, resorts and institutions across India.
Is Johkasou technology CPCB-compliant for use in India?
Yes — when properly sized and operated, a Johkasou-type FRP packaged STP consistently achieves BOD below 30 mg/L, TSS below 100 mg/L and pH in the 6.5–9.0 range required by CPCB discharge norms. Aquatic Solutions units are designed against CPCB and state PCB consent conditions, and each installation is backed by third-party lab reports. For projects where the state PCB has stricter norms, the tertiary package polishes output well below the discharge limits.
What tertiary treatment does Aquatic Solutions provide with its Johkasou STP?
The standard tertiary package includes a pressure sand filter (PSF) that removes residual suspended solids down to 10–20 microns, an activated carbon filter (ACF) that adsorbs colour, odour and dissolved organics, and UV disinfection or chlorine dosing for pathogen destruction. For the highest reuse-grade output, an optional MBR upgrade delivers turbidity under 1 NTU with a complete pathogen barrier. The tertiary skid is mounted alongside the FRP unit and delivered pre-piped.
Can the treated water from a Johkasou FRP STP be reused? For what applications?
Yes. After tertiary treatment, the water meets CPCB reuse norms and is suitable for toilet flushing (the largest demand in any building, 25–35% of total consumption), landscape and garden irrigation, vehicle and floor washing, and — with an MBR/RO upgrade — cooling tower make-up. Aquatic Solutions provides dual-plumbing advisory so flushing and irrigation lines run on treated water while potable supply remains untouched. Buildings typically cut freshwater purchase by 30–40% through reuse.
What capacities and footprint do Johkasou FRP packaged STPs come in?
Aquatic Solutions manufactures Johkasou FRP packaged STPs from 5 KLD (single villa or clinic) up to 500 KLD (townships and campuses) using parallel FRP module trains. A 5-KLD unit occupies roughly 2.5 m × 1.5 m; a 50-KLD installation fits in about 5 m × 2.5 m. Because the units are lightweight and sealed, they can be installed in basements, on terraces, in landscaped pits or above ground — wherever there is no room for a conventional RCC plant.
How long does installation take, and what maintenance does a Johkasou STP need?
Installation takes 2–5 days on site: the unit arrives factory-finished, sits on a prepared base, and is connected to the inlet, outlet and power supply — no masonry, curing or waterproofing is required. Maintenance is minimal: periodic desludging every 6–12 months, blower and diffuser checks, and routine media inspection of the tertiary skid. Aquatic Solutions offers annual maintenance contracts that include desludging, spares and performance monitoring.
Get a Quote for a Johkasou FRP Packaged STP
Tell us your project's sewage load and reuse requirements — we will size the right Johkasou FRP module, include the tertiary treatment package and provide a detailed quotation within 24 hours.