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Landfill leachate treatment

By 15 September 2016acr, case, waste

The Client
The client is part of a group operating at an International level in many sectors and is highly experienced in many aspects of environmental services. The company provides the Region with many different services including street cleaning, waste collection and transport, graveyard services, public gardens maintenance, building and management of waste disposal plants, ecological stations and phytodepuration plants. The landfill in question covers a surface of 40,000 m2 and receives about 113 m3/day of waste, producing 50 m3/day of leachate.

The Challenge
The client’s main needs, which are typical of all companies operating in this sector, was reduction in the volume of leachate to be disposed of, whilst ensuring that any streams produced can be discharged from site in accordance with environmental obligation.

Parameters of the effluent to be treated:

Parameters UM Value
Conductivity mg/l 19,090
COD mg/l 6,760
NH4 mg/l 1,700
Total Solids 105°C % 1.2
BOD5 mg/l 1,000
Total Suspended Solids mg/l 200

The solution provided
A landfill leachate treatment plant with a capacity of 55,000 l/day was installed. This plant allows a reduction of 98% of the total volume to be disposed of, with the consequent dramatic reduction of the relevant costs and fully complaying with local environmental legislation.

Pre-treatment:
pH adjustment with hydrochloric acid: in this phase, the ammonium salification occurs due to the reduction of scaling phenomena.
Degassing: degassing of leachate to reduce formation of foam within the evaporator.

Evaporation/Concentration:
Evaled® RV TC 60000: First Phase Concentration – the pre-treated leachate flows into the vacuum heat pump evaporator, with mechanical vapour recompression and forced circulation, producing a concentrate and distillate.
Evaled® AC RW 3000: Second Phase Concentration – the concentrate from the first phase is further concentrated via a hot/cold water evaporator with natural circulation and heat exchanger with scraped heating surfaces. This second phase of concentration further reduces disposal costs.The obtained substance is a semi-solid residue disposable within the same landfill, fully complying with the current local environmental regulations.

Post-treatment:
Reverse osmosis: the distillate coming from the first phase and second phase evaporators goes through a membrane polishing step, followed by treatment through an ion exchange unit and activated carbon to ensure discharge standards can be achieved.

Parameters requested by the Italian current legislation (DLgs 152/06)

Parameters UM Evaled® Results Italian law in force
COD mg/l 4 100
NH4 mg/l 0,5 5
Chloride mg/l 70 100
BOD5 mg/l 3 20