Wastewater treatment and application in the advanced nanofiltration system

The Aral Sea Region is characterized by being a very demanding consumer of industrial wastewater treatment. We studied the effects of various pretreatment methods on aluminum production. This method can be used as an alternative one in industrial wastewater treatment. The aim of multi-year study is to explore a nanofiltration as a one of the most attractive technologies for this application since nanofiltration membranes can retain ions and small organic molecules from an aqueous solution. But it is also very challenging due to the presence of salts and operating problems such as fouling, salt deposition, etc. Result becomes available thank to experimental set-up based on an ion exchange and a reverse osmosis. Results are also verified by evaluation tests and field applications showing their usage and wastewater conversion efficiency. The technological scheme includes combined water treatment plant using desalination technology and additional block functioning for an aluminum production and a temporary storage. Aluminum is to be produced of the Syr Darya river rich of it with the help of cutting-edge technology of oxide film removal and cartridge packing. This work evaluates the use of aluminum accumulated in the reaction unit by means of aluminum powder plus water module to reduce the pollutant contents of industrial wastewater quickly and effectively. The invention makes it possible to reduce the cost of aluminum by 3-4 times. Energy consumption of the desalination process was also discussed. Extracted aluminum is a superior material for industry. The high activity of aluminum to water is prohibited by a thin layer of aluminum oxide on its surface. The water treatment system with a combined phase purification and desalination may contribute up to 50 per cent to meeting the reduction of energy consumption for end product (aluminum).


Introduction
One of the major industry directions is escalating capacities requiring new sources of energy and fresh water. Integrated management within the Aral Sea region is needed to help balance competing uses of water resources of Syr Darya river. It is polluted by waste water rich of aluminum salts from processes where aluminum compounds are used as catalysts for the metathesis polymerization or ethylbenzene production. Aluminum and its alloys are widely utilized in the different industries thanks to the solid oxide film on the surfaceh leading to high corrosion resistance.
Abdel-Fatah [1] also shows the potential and place of wastewater treatment in future water supply systems, if adapted to involve renewable energy sources for cost-effective fresh water generation and distribution. Several studies [2][3][4][5][6] looked at waste water sludge, and found it potentially appropriate to produce aluminum although it would require significant technological improvement. Pal et al. [7] SEWAN-2019 IOP Conf. Series: Earth and Environmental Science 408 (2020) 012024 IOP Publishing doi:10.1088/1755-1315/408/1/012024 2 specifically drew a connection to the transfer of learning from simulation experience through examining the model of combining treatment and recirculation of leather industry wastewater. None of the proposed projects considered designing a facility able to generate aluminum and fresh water at the same time.

Materials and methods
Technological layout of the experimental facility based on water treatment and reversed electrodialysis units is shown in figure 1. To extract aluminum from the concentrated waste water and make water usable directly by people, animals and plants pretreatment of desalination plants by pressure driven membrane processes (microfiltration, ultrafiltration and nanofiltration) considered to be preferred ( fig. 1, position 4). Reusing K ru , waste treatment K t and recycling K rc indexes are applicable to analyze waste water usability. Values of indexes varies from minimum to maximum levels.
Reusing index K ru evaluates the quality of process from the economic point of view. Waste treatment index K t characterizes the share of collected waste water and recycling index K rc is used to understand the amount of recycled waste water that can be reused later [8]. The description of the experimental facility is given in table 1.

Results and discussions
During experimental activities we found that 0.05 kWh per equivalent gram is consumed to transfer salt ions from the desalination and concentration chambers if the process ends at 8%-level. Meanwhile, a specific ion flow rate through the cell membrane equals 4 equivalent grams per hour per m 2 . The enough surface is then: where Е is working absorbtion capacity, equivalent gram per m 3 ; V is workload volume, m 3 ; d is specific salt consumption, equivalent gram per equivalent gram; φ is mixing multiplicity of solution; Ф is specific ion flow rate through the cell membrane, equivalent gram per hour per m 2 ; τ is design duration of a concentration process, hour•m 2 . The amount of facilities to handle a waste solution after an ion-exchange filter is then: where n is number of cell membrane couples in one facility; S м is working surface of one cell membrane, m2; m is number of ion-exchange filters in one facility.
The reverse osmosis has evoluated to reliable and established processes and displaced traditional desalination processesmulti-stage flash distillation (MSF). Different authors [9][10][11] provide an overview of recent process improvements in reverse osmosis. These improvements contribute to the cost effectiveness of the desalination process (table 2). Consequently, the key indicator is reduction of salts releases determine the overall economic viability of the proposed operation. This represents a savings of $650 in hourly cost for every 100 m3 of treated water in the Aral Sea region on a nation-wide. Concentrating is better implemented up to salinity of 100 g/dm 3 due to only 0.04..0.05 kWh per equivalent gram of electricity is then consumed. Under the circumstances, specific ion flow rate through the cell membrane are within 5..10 equivalent gram per hour per m 2 .
The results of the chemical analysis before and after treatment in the multi-stage electrodialysis module are presented in table 3.

Conclusions
Presented ideas contribute to the cost effectiveness of the desalination process, and ensure a sustainable production of drinking water on long terms. Meanwhile, cost of aluminum in the cost of commodity decreases by 3-4 times, combined with consumption of electric power 1.5-2 times lower. In addition, a risk evaluation focusing on the Aral Sea region was conducted and the results showed that aluminum will build up in association with the water desalination. Pretreatment of desalination plants by pressure driven membrane processes (microfiltration, ultrafiltration and nanofiltration) also contributes to network and make-up water treatment facilities at a district heating plant [12,13]. Compared to chemical pretreatment; new technology is applicable (1) to prevent corrosion in distillation processes, (2) fouling in a heat pump unit [14][15][16] and (3) further growth toxic near-bottom sediments in open water sources [17].