About Secondary Battery Brine Wastewater Treatment in Zero Discharge Systems

This is the last installment of our series on secondary battery wastewater, and we will discuss the treatment process and domestic companies.

Basically, in the previous article, we discussed the problems with secondary battery wastewater.

1. Secondary battery parks are located by the sea
2. In Korea, ecotoxicity TUs are measured based on freshwater fleas, so it is difficult to accurately determine the ocean impact of salt wastewater because there are no marine reference species.
3. Waste battery recycling companies and environmental companies are also continuing to research and develop wastewater-related technologies.

Secondary battery technology is an ongoing development, so naturally, wastewater treatment is also being developed with various attempts. Today, we will introduce the processes and domestic companies that are good for basic salt wastewater treatment.

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Background of Zero Liquid Discharge (ZLD) systems and their use overseas

ZLDis perfect for brackish water

ZLD stands for zero discharge system, which is a technology that is currently at the high end of the water treatment market, like ultrapure water.

‘It is a technology that is premised on the idea of ‘zero discharge', which means that it is a technology that has the conclusion of 'water reuse'. However, ZLD is a technology that uses a lot of thermal energy and produces a lot of carbon dioxide emissions.

The ideal picture would be a more advanced ZLD approach that reduces thermal energy use and leads to zero emissions.

In my last column, I mentioned that the law of conservation of energy dictates that discharging fresh water into the ocean without reusing it will cumulatively cause the entire earth's groundwater to flow into the ocean, distorting the earth's rotation axis and resulting in groundwater depletion > water migration, as in the case of Indonesia.

The purpose of ZLD is to achieve multiple benefits. The idea is to reuse all of the water rather than waste it, leaving only the pollutants behind.

‘The scary thing about "salt wastewater" is that salts are ecotoxic, and it's much harder to capture that in TU levels in the ocean than in freshwater. It's also much less well studied in terms of health effects.

For secondary batteries, cobalt is harvested in some African countries where children are often used as laborers, and for lithium, there is a lack of in-depth research on the health effects.

The ideal system for salt wastewater is the ZLD zero discharge system from ZERO LIQUID, as salt poses unknown and unknown risks to ecosystems and life.

Key applications of ZLDs

_{Reference : Chulhwan Moon, "Zero Discharge System Policy and Technology, Future Directions", KOSEN Analysis Report}

<Power plants in the United States

ZLDs were applied in the 1970s to regulate high concentrations of flue gas desulfurization wastewater and cooling tower discharges from offshore power plants in the United States.
As the number of power plants increased and the salinity of the nearby sea increased, the number of ZLDs continued to increase, reaching 60/82 as of 2008.

The largest users of ZLD are power plants > electronics > fertilizers > chemical plants > mines.
The U.S. recently amended its legislation to prioritize ZLDs for wastewater discharges from flooring and fly ash conveyances and flue gas mercury removal systems.

<Chemical raw material production base in China

China uses fossil fuels to produce chemical raw materials and has applied ZLD primarily in coal mines. This is because most mines are located in areas with few freshwater sources, making water reuse essential.

In countries like the United States, most power plants are equipped with ZLDs, with the largest proportion of ZLDs being installed in coal>chemical plants, with ZLDs ranging from 110 to 2,300㎥.

<Textile factory in India

Textile factories that discharge more than 25 cubic meters of wastewater per day have been required to install ZLDs since 2015. As of 2008, 29 dyeing plants were equipped with ZLDs to reuse water and recover and use separated salt.
In addition to textile mills, brewing, alcohol distillation, power plants, and petrochemical plants are identified as potential markets for ZLD.

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ZLD process basics and greenhouse gas issues

The basic ZLD technology has been the use of ‘thermal continuous process evaporation'.

The approximate process of the ZLD system is shown below. It can be roughly categorized into two stages: pre-treatment and post-treatment of concentrate.

Pretreatment (descaling of ions) > Raw water (demineralized concentrate) > Brine concentrator (MVC) > Brine crystallize or evaporation ponds

• Salt concentrators consume large amounts of energy and use expensive materials to prevent corrosion.
• Brine crystallizers are for additional water recovery and require three times the energy of a concentrator.

_{Source:Making Waves; Zero liquid discharge for sustainable industrial effluent management, Water (2021), 13, 2852. https://doi.org/10.3390/w1320285}

Because ZLDs use so much energy, reducing the amount of wastewater entering the crystallizer is necessary to reduce operating costs, and because they produce so many greenhouse gas emissions, a variety of technologies are being used in parallel with ZLDs to reduce these emissions.

Technologies added to ZLD's process - efficiency and greenhouse gases

Technical name	Pros	Limiting factors	Energy consumption
RO Reverse osmosis	Low energy use High technology maturity Modularized	Low processable salt concentration (up to 70,000 mg/L) Membrane fouling	Seawater: 2 to 6 kWh/m3 produced water Radix: 1.5 to 2.5 kWh/m3 produced water
ED/EDR Electrodialysis	High processable salt concentration (up to 100,000 ppm) Even if the concentration of silica is high, the membrane Fewer salts Modularized	Highly salty wastewater It takes a lot of energy to process. What it takes and how much it costs If the treatment of non-charged contaminants is Difficulty	7-15 kWh/㎥ raw water (Circles with salt concentrations above 15,000 mg/L number)
FO Isosmosis	High processable salt concentration (up to 200,000 ppm) Low-temperature heat sources are also available Modularized	Low permeability even at high salt Contaminant Migration in Induced Solutions Possible contamination of treated water due to Lack of field use cases	21 kWh/㎥ raw water (The salt concentration of the raw water is 73,000 mg/L, For a recovery rate of 64%)
MD Separators	High processable salt concentration (up to 200,000 ppm) Low-temperature heat sources are also available Less membrane fouling Modularized	Low permeability and recovery Poor treated water quality when wetting the separator If volatile contaminants are present, after Requires genus processing Lack of field use cases	40-45 kWh/m3 produced water 22 to 67 kWh/m3 produced water
MVC Salinity Concentrator	High technology maturity High processable salt concentration (up to 200,000 ppm)	Requires large amounts of energy High setup and operational costs Operating at high temperatures Not modularized	20-25 kWh/m3 raw water 28-39 kWh/m3 raw water

_{Source : Zero Discharge System Policy and Technology, Future Directions | Chulhwan Moon (Trends Report) https://kosen.kr/info/kosen/REPORT_0000000001061}

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About ZLD Equipment

1. Doosan Heavy Industries & Construction's high capacity zero discharge system

_{Source: https://www.doosanenerbility.com/heavy_file/business/data/water_epc/Water_plants_10th_Edition_kr.pdf}

Doosan Heavy Industries & Construction had a variety of seawater desalination technologies based on its ability to build the world's largest desalination plant in the Middle East. As explained above, ZLD is possible only with sufficient experience and infrastructure in RO technology, so Doosan had the technology to order large quantities of ZLD.

Generally, zero-discharge treatment facilities are based on reverse osmosis (RO) or evaporation technologies and are deployed in conjunction with various wastewater treatment processes such as softening, biological treatment, MF/UF, and others, depending on the characteristics and conditions of the wastewater at the source.

As the world's largest seawater desalination supplier, Doosan Heavy Industries & Construction's know-how in evaporation technologies such as multi-stage evaporation (MSF) and multi-effect (MED), as well as reverse osmosis processes, has enabled it to develop a zero-discharge treatment facility (120m³/d), and is in the process of expanding its capacity to more than 4,000 m³/d. In addition, the company is undertaking a zero-discharge treatment facility project at a petrochemical facility in Saudi Arabia, the first of its kind in Korea.

2. WelchronHantec's ZLD

_{Source: WelchronHantech official website : http://www.hantec.co.kr/html/energy05.asp}

Welchron Hantech is a company with a variety of technologies related to secondary batteries.

Lithium extraction facilities (Concentrated Crystal Facility), recycling facilities, separation membrane facilities, and wastewater treatment facilities.

We provide crystallizer facilities for mining lithium and nickel, which are raw materials for secondary batteries, recycling facilities for recycling resources, and finally wastewater treatment.

3. KistEngineer - Vacuum Evaporative Concentrator and NMP Solvent Regenerator

_{Source: KistEngineer Official Blog : https://blog.naver.com/dhsung73/223226796524}

KistEngineer's KISTHYDROMAT Vacuum Evaporative Concentration SystemThe most outstanding feature of Less energy(6,000~10,000 won per ton).
The closed-system control of thermal energy ensures that no additional energy is required beyond the power required to operate the vacuum pump alone.

It is an energy circulation type system that boils and condenses wastewater by operating a vacuum pump without supplying a separate heat source (electric heater, gas, steam) and explains that it is an evaporative concentration system that reduces the cost of wastewater treatment and is inexpensive to operate.

The 90%'s clean water can be recovered and reused or discharged/non-discharged, describing the benefits below.

• Only effluent from 10% is concentrated
• Evaporative concentration at low temperature operation due to processing under vacuum
• Environmentally safe design
• Automatic cleaning
• Low operating costs

KistEngineer's NMP Solvent RegeneratorThe

The cost of the NMP (N-Methyl-2-Pyrrolidinone) solvent used in the preparation of the cathode active material in this lithium-ion production process is a significant contributor to production costs.

KistEngine's NMP solvent regenerator can be applied to the recovery process of NMP, helping to reduce the cost of the secondary battery process.

Secondary Battery Industry Insights Series

Vol.1 Saemangeum Secondary Battery Wastewater Information Insight Vol.1 : View

Vol.2 What is Secondary Battery Brine Wastewater? ARK Environment : View

Vol.3 Lithium Mining and Environmental Impact Assessment - Secondary Battery Insightsvol.3 : View

Vol.4 Zero Liquid Discharge (ZLD) and Secondary Battery Wastewater - Background, Pros and Cons : View

Vol.5 List of domestic companies related to secondary battery wastewater treatment : View