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TAS Industrial wastewater treatment plant, Ravenna

Located at the Baiona Ecological Centre, Via Baiona Ravenna

  • 1 / 1   ndustrial wastewater treatment plant, Ravenna

The plant, located in the Baiona Ecological Centre in Ravenna, is authorised to treat industrial wastewater from firms in the Ravenna Chemical Industry District and special liquid waste, including hazardous waste, generated and delivered by third parties in tankers.

Page updated 26 August 2015

 
    Planned flow rate of organic process water treatment section
    1,200 m/hr
    COD treatment capacity of organic process water treatment section
    1,300 kg/hr
    TKN treatment capacity of organic process water treatment section
    60 kg/hr
    Planned flow rate of inorganic process water treatment section
    2,000 m/hr
    Organic process water treatment section authorised to treat
    110,000 tonnes/year of special liquid waste, including hazardous waste
    Authorised disposal codes
    D8/D9
    Increase in authorised capacity
    200,000 tonnes/year

    The plant is divided into three main sections:

    • Treatment section for organic process wastewater and liquid waste (TAPO)
    • Treatment section for inorganic process wastewater (TAPI)
    • Treatment section for sludge

    The treatment section for organic process wastewater and liquid waste (TAPO) comprises a complex series of treatment phases:

    • Physicochemical pre-treatment of special liquid waste arriving in tankers: Designed mainly for the abatement of heavy metals, this takes place in a special facility through the addition of calcium hydroxide, ferric chloride, complexant for heavy metals and polyelectrolyte; the treatment unit is completed by the thickening and centrifugation of the sludge, which is separated for disposal;
    • Primary treatment: Includes the separation of suspended solids and the abatement of part of the organic load of the waters. The dedicated unit receives and treats organic process wastewater arriving via a pipe coming from the Ravenna Chemical Industry District and via tankers from third parties. The current flow rate of the plant in normal operating conditions is 1,200 m per hour. Specifically, primary treatment includes:
    • Flocculation: Ferrous chloride is added in a dedicated tank and, depending on the acidity of the current, a milk of lime solution is used to keep the pH between 8 and 9 and an anionic polyelectrolyte encourages flocculation;
    • Clarification: The suspension produced through flocculation travels through the effect of gravity to two primary clarifiers, operating in parallel, for the abatement of heavy solid substances and part of the organic load. The sludge extracted from the two clarifiers is sent for sludge treatment where, first of all, it is screened by means of two vibrating screens. The coarser solid part is separated and sent for incineration in incinerator F3 and the sludge suspension is sent to the thickening unit;
    • Flotation: The effluent water from the clarifiers goes to two floatation systems where the light suspended parts, both solid and oily, which have difficulty sedimenting, plus a further amount of organic load, are removed. The water treated in the two floatation systems is sent to a 20,000 m equalisation tank before the following biological treatment. The foam and the light sludge extracted are sent to the sludge treatment section.
    • Biological treatment: This comprises the pre-anoxic denitrification stage for the nitrates present/recirculated, followed by the aerobic oxidation of the COD and the ammoniacal nitrogen. These phases take place in two "biological towers", each with a capacity of 16,500 m in which the pollutants are biodegraded by specific bacterial populations. The treatment is completed by the post-denitrification and post-aeration stages which take place in a covered tank, with the aspiration and treatment of the gaseous effluents through biofiltration. The sludge is decanted in three final sedimentation tanks which operate in parallel; one part of the sludge is recirculated for treatment while the residual part, the so-called excess sludge is channelled to the sludge treatment section. The clarified waters then move on to the last stage, filtration.
    • Filtration: The filtration unit comprises 6 constant flow rate gravity filters, with a double layer of sand and anthracite, which have the function of further reducing the suspended solids as well as the COD and the nitrogen in the sludge flocs. Before being released into external surface water, following filtration the water is subjected to the final aeration phase and, if applicable, chlorination in a special tank.

    The inorganic process wastewater treatment section (TAPI) is used for the abatement of suspended solids in wastewater that arrives via pipes from the Ravenna Chemical Industry District plants. This section receives both the industrial water which does not come into contact with process fluids and the runoff water coming from non-critical paved areas, as well as drain water from the F3 incinerator cooling towers. The TAPI section includes the following phases:

    • Screening, storage and sedimentation. The inorganic process waters are screened before being sent to a natural sedimentation tank with a volume of 10,000 m, which is also used for accumulation. In the tank, the low water speed allows the solid particles present to sediment; the sludge formed by the process is sent to the sludge treatment section;
    • Accelerated clariflocculation. The water leaving the sedimentation tank is sent to a distribution well where the necessary flocculants are added. From there, the current is transferred through the effect of gravity to two accelerated clarifiers with an overall capacity of 2,000 m per hour where further sedimentation of suspended solids takes place. The sludge separated in the two accelerated clarifiers is sent to the sludge treatment section, while the purified water is transferred to the final aeration tank which also receives the TAPO line waters before being discharged into surface water.

    All sludge produced during the process is treated in the sludge treatment section. The thickened chemical sludge (TAPO and TAPI lines) and the excess biological sludge are centrifuged and dried using a turbo dryer and sent to landfills for disposal.

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