Used water still has value
Water enters the plant, leaves as wastewater, and part of it can return for reuse. Solid waste is similar: calculated properly, it becomes material.
Domestic and process water
Domestic water
Treating groundwater and surface water for housing, buildings and schools to the current domestic water standard.
Process water
Water for boilers, cooling, food, pharmaceuticals and electronics. Each industry has its own limits, so the technologies are combined to the quality required. See the six technologies →
Wastewater treatment
Domestic
Buildings, residential areas and industrial parks. AO, MBBR or MBR depending on footprint and effluent target.
Medical
Biological AO or MBR, always with disinfection before discharge.
Industrial
Start by analyzing each stream, then combine physico-chemical, biological and advanced oxidation steps to meet discharge limits.
Textile dyeing
Equalization, cooling when the water is hot, coagulation, biological treatment, then color removal with Fenton or ozone.
Electroplating
Separate chromium, cyanide and acid-alkali streams, treat each physico-chemically, then collect the precipitate and filter.
Common technologies
AO
Anoxic then aerobic, removing organics and nitrogen.
MBBR
Moving media hold the biomass and raise the load per tank volume.
MBR
Membranes replace the clarifier, giving clear effluent on a small footprint.
DAF
Fine bubbles float oil, grease and solids. Suited to food, seafood and paper.
Physico-chemical
pH adjustment, coagulation, flocculation and settling. Doses must be set by jar test.
AOPs
Ozone, UV, H₂O₂ and Fenton create strong radicals for persistent organics. Results depend on the water matrix.
Water reuse: MLD and ZLD
MLD
Minimal Liquid Discharge: cutting wastewater discharge as far as practical and returning most of it to use.
ZLD
Zero Liquid Discharge: no liquid leaves the site, and what remains is concentrated into solids.
250 m³/day in Hưng Yên
Reusing 60% of hazardous wastewater after treatment, brought back to domestic water quality.
Solid waste recycling
Portland cement must be fired at around 1,450°C and emits a great deal of CO₂. I research a different route, inorganic nano polymer concrete: an aluminosilicate binder forms in a strongly alkaline medium below 100°C and binds sand, clay and waste. The concrete needs no water curing, hardens as it dries, and can be adjusted across grades 50-600.
Gypsum residue into building materials
Gypsum residue from DAP fertilizer production is ultra-fine, around pH 2, and high in PO₄ and F. After treatment the acid is neutralized and the residue sets into a durable mass that does not break down in water, reaching grade 80-500. It is used for bricks, blinding concrete and road materials.
Thermal power ash and metallurgical slag
Reusing thermal power ash with a high slag content and metallurgical furnace slag in building materials. Blast furnace slag is porous and light, which suits lightweight concrete, unfired bricks and wall panels.
Unfired bricks from hill soil and saline sand
At grades 50-100 the mix uses locally available material such as hill soil, saline or fresh black sand, and construction waste. Uses include unfired bricks, low and medium class roads, and the base layer of higher class roads.
| Material | Laboratory | Test samples | Small-scale production |
|---|---|---|---|
| Gypsum residue | Done | Done | Ready |
| Thermal power ash | Done | Done | Ready |
| Metallurgical furnace slag | Done | Done | Ready |
| Dredged sludge from estuaries and ports | Done | Not yet | Not yet |
| Inert industrial waste | Done | Not yet | Not yet |
| Bauxite residue | Done | Done | Not yet |
| Saline sand | Done | Done | Ready |
| Construction waste and stone dust | Done | Done | Ready |
