ENV · Zero liquid discharge
Zero liquid discharge (ZLD) systems
Recover close to all of your effluent, meet a no-discharge condition, and turn the residue into compost, fuel, fertiliser or saleable salt rather than a disposal line item.
The starting point
What problem does it solve?
- “Our wastewater is costing us too much”
- “We're struggling to meet discharge regulations”
- “We can't expand because of water limits”
- “There is nowhere left to send the brine”
- “Our RO reject has become the whole problem”
Your solution can be ZLD.
Zero liquid discharge is one of the most effective methods available for treating industrial wastewater with high salinity, and it is usually the final stage of a treatment strategy rather than the first move. In the ZLD process, advanced technologies and equipment separate contaminants from the wastewater until the level of contaminants in the water is reduced to nearly zero.
What it actually solves is a constraint. A site that cannot discharge cannot expand. A site whose consent has tightened is running on borrowed time. A site paying to tanker brine away is funding somebody else's evaporation pond. ZLD removes the constraint by closing the water balance and converting the dissolved load into a solid you can manage.
It is not free, and we will say so early. The honest comparison is against minimum liquid discharge, which recovers around 85% of the stream on membranes alone at materially lower cost. If your consent allows a small concentrated discharge, MLD usually wins. If it does not, ZLD is the answer — and pre-treatment design decides what it costs.
Why it pays
Benefits
Near-total recovery
Complete treatment of process wastewater producing clean, high-quality water with nearly 100% recovery. Water leaving the evaporator carries total dissolved solids below 100 ppm — good enough for cooling tower make-up and boiler feed.
The residue becomes a product
Depending on the incoming wastewater, the solid output can become organic compost, backup fuel for an incinerator, organic fertiliser, animal feed, or recovered salt that is either reintroduced to the process or sold.
Runs unattended
The system operates 24/7. Cleaning is automatic, using clean-in-place and rinsing cycles without operator intervention, which keeps day-to-day labour off the operating cost.
Compliance that does not move
With no liquid discharge there is no discharge consent to breach. For sites in water-stressed regions or under tightening regulation, that removes an entire category of operating risk.
Evaporator choice, not evaporator dogma
We offer multi-effect evaporators, mechanical vapour recompression, multi-stage flash and forced circulation evaporators. Companies that offer only one evaporation method will always recommend it.
Designed down from pre-treatment
We design the pre-treatment stage specifically to reduce cost in the evaporation and crystallisation stages, which lowers investment cost and produces the most appropriate final output.
Process
How it works
The operational stages of a ZLD system are designed around three things: the characteristics of the wastewater — volume, composition and variability — the desired level of water recovery, and the economics of the site. It is not possible to determine the process steps precisely without enough information about the wastewater. The contaminants have to be identified first; the roadmap follows from them.
In general terms, the process resolves into five stages. Pre-treatment is the one that decides the cost of everything after it.
Process diagram
Pre-treatment → evaporation → crystallisation → drying → output management
Reserved for a static ZLD block-flow diagram showing feed, pre-treatment options (DAF, RO, UF, CCRO™, HART™), evaporator selection, crystalliser, centrifuge, dryer and the five solid output routes, with condensate and filtrate recycles marked.
Static process diagram — final artwork to be supplied.
Pre-treatment
One of the crucial stages, and for complex input streams it can be more complex than the evaporator stage itself. It improves system performance, reduces the number of evaporators required and therefore lowers overall cost. Methods used include dissolved air flotation, reverse osmosis, ultrafiltration, CCRO™, HART™ and others, selected according to the feed stream and what the evaporators need to see.
Evaporation
After pre-treatment the wastewater enters the evaporators. The method is chosen against process conditions, effluent properties and volume. Glorinda offers multi-effect evaporators (MEE), mechanical vapour recompression, multi-stage flash (MSF) and forced circulation evaporators (FCE), and the stage may involve several steps. The choice affects overall efficiency, energy use, initial investment, operating cost and maintenance cost. Output water is crystal clear with total dissolved solids below 100 ppm, suitable for reuse in cooling towers and boiler feed.
Crystallisation
Separates dissolved solids from the concentrated brine generated during evaporation. That brine carries a high load of dissolved salts and other non-volatile components; crystallisation recovers them as a solid product and sharply reduces the final liquid waste volume. The output then passes to a centrifuge, which reduces moisture content significantly and minimises the duty on the dryer. The stage involves three steps: generation of supersaturation, relieving of supersaturation, and control of supersaturation.
Drying
The portion of the stream that remains inadequately dried after crystallisation enters the dryer from the pusher centrifuge for complete water removal. This is the final step and it determines the moisture content of the output. Energy consumption is a design priority here, and air ventilation is incorporated so that dust from crystallisation and salt particles does not disperse into the surroundings. Dryer types include scraped surface dryers, agitated thin-film dryers (ATFD), steam tube bundle rotary dryers, spray dryers and fluidised bed dryers.
Managing the solid output
Five routes, in order of preference. Conversion to organic compost by reducing moisture to 30% w/w where the production line contains organic material. Incineration at approximately 70% w/w concentration using a backup fuel such as wood waste, bagasse or other organic residues in a standard boiler, serving as an energy source. Use as organic fertiliser or animal feed as a dry non-hygroscopic powder at 98% weight concentration — in alcohol production and yeast-containing lines the output may contain over 20% organic carbon and up to 17% potassium. Where the effluent contains valuable salts, crystallisation separates them into powder to be reintroduced or sold. Where none of these is feasible, disposal follows industrial guidelines through complete drying or landfill.
What we do on a ZLD project
- Analyse wastewater specifications and your disposal goals against the environmental standards that apply.
- Select the method and the technologies for pre-treatment, evaporation and crystallisation, and any other required components.
- Procure materials and equipment from in-area manufacturers or use Glorinda-developed technologies, depending on what the project needs.
- Install the system.
- Commission and operate.
- Train your operators.
- Provide after-sales services.
Where the cost sits
Three levers dominate. First, pre-treatment: every kilogram of solids and every scaling species removed before the evaporator is capacity you do not have to buy. Second, evaporator selection: MEE, MVR, MSF and FCE have very different energy and maintenance profiles, and matching that profile to the utilities you already have on site is where the operating cost is set. Third, the solid output route: a residue that can be composted, burned or sold behaves completely differently on the balance sheet from one that has to be landfilled as hazardous waste.
Applications
Where it is used
ZLD technology is designed and customised to the customer's needs and is used for treating wastewater across a wide range of industries.
Industries
- Oil, gas and petrochemical
- Power generation
- Food and livestock
- Cement
- Steel
- Rubber manufacturing
- Consumer goods manufacturing (CGMF)
- Pharmaceutical
- Mining
- Textile
- Wood and paper
- Electronic industries
- Palm oil
- Municipal wastewater treatment
Typical applications
- Concentration of RO reject
- Concentration and disposal of high COD streams
- Recovery of dissolved solids
- Solvent recovery
- Cooling tower blowdown that has nowhere to go
- FGD wastewater from coal-fired power plants
- High-TDS effluent from reactive dyeing and printing
- Ammonia and nitrogen-bearing condensate from fertilizer plants
- Sites operating under a zero-discharge permit condition
Equipment
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Over 200 types — cation, anion, mixed bed, chelating, adsorbent and chromatography media, with resin screening and process design support.
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TOC, oil-in-water, pH, conductivity, dissolved oxygen and CEMS packages with sampling systems and shelters.
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Vacuum and compression duties across wastewater, chemical, paper and power applications, including explosion-protected models.
Read moreSteam turbines
50 kW to 180 MW plus energy recovery sets that convert surplus steam pressure into power.
Read moreEngineering services
Engineering support for this technology
Selecting a process is an engineering decision, not a purchasing one. We run feasibility and pre-feasibility studies, characterise the stream, compare the routes on capital and operating cost, and act as owner's engineer while somebody else builds it if that suits you better.
Evidence
Projects
Sample layout. Reference projects are being cleared for publication with the clients concerned. The structure below is final; the content is placeholder.
SampleWater reuse retrofit — sample card
Card layout for a completed water reuse project: stream data before and after, recovery achieved, scope Glorinda held, and the client's own words.
SampleZLD package — sample card
Card layout for a zero liquid discharge package: feed characterisation, evaporator type selected, solid output route, and commissioning duration.
SampleOwner's engineer mandate — sample card
Card layout for an advisory mandate: the client's decision, the options assessed, and what changed in the tender as a result.
FAQ
Questions engineers ask
Taken from the questions procurement teams, plant managers and consultants actually send us.
What is ZLD?
Zero liquid discharge is a treatment strategy in which no liquid effluent leaves the site. Water is recovered for reuse and the dissolved load is converted into a solid. In practice it is a sequence — pre-treatment, evaporation, crystallisation, drying and solid output management — rather than a single piece of equipment.
How can I reduce the operating cost of a ZLD plant?
Mostly upstream of the evaporator. Effective pre-treatment reduces the number of evaporators required and lowers overall cost. Matching the evaporator type to the utilities you already have — waste steam, surplus power, available cooling — is the second lever. The third is finding a solid output route with value: compost, backup fuel, fertiliser, animal feed or saleable salt all beat hazardous disposal.
Do you have a ZLD system that fits my industry?
ZLD is designed and customised to the specific wastewater rather than sold as a standard model. We have designed for oil and gas, petrochemical, power, textile, pharmaceutical, food, cement, steel, mining, paper, electronics and municipal applications. The starting point in every case is the wastewater analysis.
Can Glorinda deliver the complete ZLD package?
Yes. We take a comprehensive approach to executing ZLD projects, overseeing the process from pre-treatment to the final stages: analysis, technology selection, procurement, installation, commissioning, operation, operator training and after-sales services. We also supply single stages into a wider EPC scope.
How clean is the recovered water?
The output water from the evaporator is crystal clear, with total dissolved solids below 100 ppm, indicating nearly 100% recovery. That is suitable for reuse in processes such as cooling towers and boiler feed. Where a higher grade is needed, ion exchange and EDI polish it further.
Is ZLD always the right answer?
No, and we will tell you when it is not. If your consent permits a small, concentrated discharge, minimum liquid discharge recovers around 85% of the stream using membranes alone and is considerably cheaper to build and run. ZLD is the answer when discharge is genuinely unavailable or when the recovered salt has value.
Conversion
Take this further
Send us the stream data, the discharge limit or the equipment list you are working from. An engineer reads every enquiry and replies with the questions that actually decide the solution — not a brochure.