Wastewater treatment plants for villas, hotels and complexes in Bali

Sizing starts with people, not bedrooms. We work from roughly 150 to 200 litres per person per day, add staff and the kitchen, count the guests a property actually sleeps rather than the number on the listing, then allow retention time for the treatment stage to do its work. A hotel restaurant, a spa or a laundry changes the load far more than one extra room — so we ask for occupancy data and water bills before we draw anything.

What happens after treatment matters as much as the plant. In the clay around Canggu and Kerobokan a soak pit that works in August is a pond by January, so effluent needs a drainage field or reuse-grade water for irrigation. On the limestone of the Bukit the opposite is true: everything disappears instantly, straight towards the water table — which is why we never discharge untreated effluent into bottomless pits there.

STP sizing by guests, units and staff

These are the indicative loads we start from. The final figure comes from your occupancy pattern, but the order of magnitude tells you early whether you need a packaged unit or a plant with its own equalisation and sludge handling.

Indicative flows at 150–200 L per guest per day. Kitchens get a grease trap ahead of the plant; properties with uneven occupancy get an equalisation tank so weekend peaks do not wash the biology out.

The plant is only as good as what reaches it, so we size it together with the plumbing and drainage rough-in — vented lines, inspection chambers and falls that carry flow without blockages. On villa complexes one shared plant usually beats a tank per unit: one service contract, one effluent route and one log, which is how we plan the shared works in our villa complex construction projects.

What DLH checks — and the documents we hand over

Hotels, guesthouses and larger villa complexes operate under an environmental approval — SPPL, UKL-UPL or AMDAL depending on scale — and the environmental agency (Dinas Lingkungan Hidup, DLH) expects treated effluent to meet the national domestic wastewater standard, Permen LHK 68/2016: for example BOD 30 mg/L, COD 100 mg/L and TSS 30 mg/L. The approval itself is filed by the owner or an environmental consultant. Our part is the technical file and a plant that meets the numbers in daily use, not only on the day of inspection:

• Sizing calculation and process flow diagram
• As-built drawings of the plant and effluent route
• Commissioning record: seeding, flow and blower checks
• Effluent sample arranged for an accredited laboratory
• Operation & maintenance manual for your staff
• Service log, filled in at every visit

Maintenance: service visits and written logs

A treatment plant is a living process. Blowers keep the aerobic stage alive, diffusers clog, sludge builds up, and disinfection needs dosing. On a quarterly contract we check all of it, record effluent clarity and sludge depth, and write the findings into the plant's log — the document a hotel manager hands to an inspector and the first thing we read when something smells wrong. Service runs from IDR 1,850,000 per quarter, desludging quoted separately.

Three failures account for most of the emergency calls. Flotation: an empty plastic tank in a high water table lifts like a boat and cracks its inlet, so ours sit on an anti-flotation slab with straps, backfilled in stages with the tank part-filled. Overloading: a system sized for a family and then run as a six-bedroom rental, which turns a two-year desludging cycle into six months. And proximity: a plant or tank upgradient of a well, or within about ten metres of one, will contaminate it — so we site them downgradient wherever the plot allows, and specify treatment rather than distance where it does not.

Just a household septic tank? For a single family home a sealed bio septic unit is usually enough: a 3 m³ unit, installed and commissioned from IDR 21,500,000, serves a household of five to eight. We install them as part of our own builds; the sizing logic is the same, only smaller. Why water and wastewater come first on a small island is covered in our note on sustainable construction in Bali.