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    Abstract

    WASATEX PROJECT

    The project aims to get water reusable into industrial production cycle through wastewater treatment.
    The total recycling of water is a prerequisite for reducing the environmental impact of industrial processes. The lack of global water resources makes it is necessary to treat water as a valuable asset, not only in specific areas of the world affected by drought, but also in Western Europe, where water resources, although available, have a high industrial cost.

    OLIMPIAS TEKSTIL doo, ASPEL Srl and EUROPROGETTI Srl. are realizing the Wasatex project.
    It is started in July 2014 and it will be completed within December 2016.

    This project is co-funded by the European Union within the CIP Eco-Innovation initiative (http://ec.europa.eu/environment/eco-innovation) of the Competitiveness and Innovation Framework Programme, CIP (http://ec.europa.eu/cip/)

    For the industrial development of the project, the textile factory in Osijek (Croatia) of Olimpias Tekstil group was chosen. The company currently uses only 5-10% of treated water in production processes. 
    The objective of the project is to recycle up to 90% of the treated water. 

    Situation before the Project

    Olimpias Tekstil is an establishment where dyeing and finishing cycles of textile fibers, primarily cotton and wool, are made.
    It occupies an area of about 81.000 square meters in an industrial district in which production units, residential homes and places of community reside.
    The company produces up to 8.000 kg/day of yarn and about 290 people work here.
    The waters conveyed to the treatment plant come mainly from the processes of finishing of yarns and fabrics.
    The phases of the dyeing and finishing of textile materials are particularly impactful from the environmental point of view, because:

    • They require large volumes of water
    • They are energy intensive
    • They produce air emissions and wastewater laden with pollutants, especially organic matter (COD and BOD5), salts (chlorides, sulfates and hardness), dye molecules and surfactants.

    The existing water treatment plant was built more than 10 years ago and is constituted by a biological unit with a classic final clarifier, designed to treat the wastewater from the textile plant and discharging them into the sewer. The water needed for industrial processes is completely pumped out from the well, about 1.600 m3/day, equivalent to the needs of 10.600 people.

    The function of water treatment plant

    Purify water and allow their industrial reuse is a duty to the environment and condition for acquiring production efficiency by reducing costs related to the use of natural resources.
    The biological process, currently adopted in the establishment of Osijek, effectively removes COD, BOD5, surfactants, oils and fats, nitrogen, phosphorus and suspended solids with the linked concentration of colloids and it is also partially operative with the color. It does not remove inorganic components such as hardness, alkalinity, silica, chlorides, sulfates and heavy metals. This makes impossible to reuse the treated water into production processes.
    To use the outlet water from the biological unit, it is necessary to perform other treatments to remove suspended solids, color, hardness and alkalinity and reach the chemical-physical water characteristics suitable for the processes of washing and fabrics’ rinsing. The total removal of the salinity is instead necessary to make the final water also suitable for the processes of dyeing and finishing.

    The implementation of the existing biological system, developed by Wasatex project, involves the following systems:

    1. Membrane Bioreactor (MBR),able to separate completely suspended solids, biomass, bacteria and microbes present in the oxidation basin. The output water is very clear (NTU <1) and contains a very low concentration of organic matter, a fraction of color and the inlet salinity.
    2. Resin filter, for the removal of the residual color, COD and surfactants.
    3. Softener filter and Decarbonating tower, to remove the hardness of calcium and magnesium and the alkalinity.
    4. Reverse osmosis (RO), to eliminate the soluble salts such as sulfates, chlorides, in addition to the residual COD, silica, alkalinity, etc.
    5. Nanofiltration (NF) to treat the RO’s rejections and separate monovalent salts, such as Sodium Chloride, from other compounds contained in solution, obtaining a brine (NaCl) that can be reused either as a saline agent to the dye baths, both for the regeneration of the softening filters.
    6. OX system, to destroy and then remove the complex molecules with high molecular weight, such as COD and color,concentrated in NF’s rejection, through radical group OH –.

    Expected Results

    With the addition of new purifying units of Wasatex project, up to 90% of the water can be reused in the industrial processes and the amount of water pumped from the well will be lower than 65% (equivalent to a reduction of 1.020 m3/day). This allows a remarkable water saving, a cost saving of water extraction and its discharge and the cost reduction of primary water treatments (softening and iron removal filters).
    The environmental benefit is obvious:

    • Lower consumption of natural resources to heat the water (recycled water has a temperature of about 30 °C against 15 °C of well water),
      Reduction of gas emissions and a cost saving relating to the fuel.

    The water, coming out from the decarbonating tower, after the biological treatments, filtration with MBR, color removal through RF and hardness reduction through SF, has the necessary characteristics to be used in washing operations after treatment of soaping. The reused water is about 300 m3/day.
    The water, coming out from the RO, has a quality so high that it can be reused for preparing the dyeing baths, for the execution of the bleaching and in all those industrial processes where are required parameters with very low limits of salinity and hardness. This characteristic allows obtaining technically more stable colors, superior light fastness, better yields of the dye, less use of sequestering agents and chemical agents in baths of dyeing and finishing. Furthermore, the operation of bleaching is much more efficient and stable over time, since alkali salts are not deposited on the fiber, and also a reduction in the use of the optical bleached is reached.
    The permeate produced by the RO membranes, as well as being excellent from the qualitative point of view, also guarantees the stability and repeatability of its characteristics over time; this avoids problems of color reproducibility and uniformity during the whole year, which are usually caused by seasonal variations of the primary water (summer-winter).
    The permeate of the RO is characterized by a very low salinity and a concentration of silica and hardness equal to zero, so it can also be used to feed the boiler for the steam production, reducing the consumption of chemical agents.
    The brine, coming out from the NF (permeate) that treats the RO’s rejections, can be used in the regeneration of the softener filters or like a saline agent for dyeing baths.

    Structural Requirements

    The revamping of Osijek plant did not require major structural alterations. It involves the:

    • Use an existing warehouse to place the sections of resin filter, softener, RO and NF, and resize the current equalization tank to obtain the storage tanks of treated water and place the unit of MBR.
    • Build a new technical room, close to the existing tanks, as shown in the following figure.

    Plants layoutFigure 1: Plant’s layout: new civil works in red; new machineries and equipment in different colors; existing plant in gray

    During the implementation of the plant, it will not need to suspend or modify the normal cycles of factory’s production, because a temporary bypass of the equalization tank will be set up in order to allow the biological processes also during the work of upgrade.

    Few data confirming the sustainability of Wasatex

    The Wasatex project can produce water reusable in industrial processes, reducing the consumption of water resources, the fuel consumption for its heating and reducing the related CO2 emissions.
    With the plant revamping, a reduction of 1.020 m3/day of water, from the current 1.600 m3/day to the expected 580 m3/day, will be reached.

    saving of incoming water

    Considering the recycled water has an average temperature of 30 °C, against a temperature of 15 °C of the well water, there will get an energy saving since the industrial boiler will heat the water up to the operating temperature, starting from a temperature of 30 °C instead of 15 °C.

    power savings

    Considering that CO2 emissions due to burned natural gas is equal to 2.276 g/Nm3 and that there is a reduction of natural gas consumption of 1.832 Nm3/day, CO2 emissions can be reduced of about 4.170 kgCO2/day, amounted to 1.251 tons CO2/year.

    The recycling of the treated water is also ECONOMICALLY FAVOURABLE, in fact in this case it can be reached a cost savings related to plant management of almost 400.000 €/year, basing the calculations on the following data:

    Working days per year 300 gg/anno Cost of pretreatment of well water 0,16 €/m³
    Cost of well water 0,24 €/m³ Cost of natural gas 0,473 €/Nm³
    Cost of water discharge 0,65 /m³ Cost of plant O&M 0,45 €/m³

    yearly net saving

    Therefore, the Wasatex project involves improvements both in terms of technical - economical, both in terms of ecological and social (reduction of environmental impact), consolidating the company's eco-friendly image in a world increasingly focused on compliance and environmental protection.


    The technology that benefits the environment and improves the productive performances

    Other benefits result from this innovative technology and are obtained thanks to the high quality of produced water (RO permeate):

    1. The permeate water has chemical characteristics such as to facilitate the processes of finishing, as well as the repetition of these processes.
    2. The quality of permeate water is technically perfect and stable. There are not seasonal variations in the characteristics of the water. This avoids adjustments on dyeing recipes, during the year, ensuring the repeatability of dyes.
    3. The colors of yarn and fabrics are more stable, both to the rubbing and in the light. They are also more brilliant, because they are not opacified by the presence of salts.
    4. In the dyeing processes, chemicals such as soaps, sequestering and equalizing are used in reduced quantity.
    5. Fewer number of dyeing’s remaking is necessary to correct tone variations, due to water quality.
    6. The permeate water can be used also in boilers: in this way, it is possible to save chemical products, such as sequestering agents, to do not dirty the pipes of the heat exchanger, to reduce maintenance, to maintain high yield of water-vapor exchange and to optimize the energy consumption. Additionally, the drains of the boiler are reduced, with a consequent energy saving (the temperature of the purge is about 90 °C).

    The Wasatex technology is TAILOR-MADE and FLEXIBLE: according to the characteristics of the water to be treated, to customer requirements and local restrictions, a solution tailored to the specific situation will be designed, inserting new technologies also in existing plants as per the Osijek installation.