Wastewater and Odour Control

NEUTRA-MILL WATER TEATMENT SYSTEM – CASE STUDY

WASTEWATER/ODOUR CONTROL MELBOURNE SAND BELT

• pH raised
• Multiple water bodies treated
• Aqueous metal concentrations lowered
• Noxious odours (hydrogen sulphide, ammonia) controlled
• Treatment precipitates deposited within on-site water impoundments
• Achieved discharge standards for release into the stormwater system

LOCATION

Melbourne, Australia. 30 kilometres south-east of the city centre (Latitude: 37° 55′ S, Longitude: 145° 8′ E).

SETTING AND CLIMATE

The Melbourne sand belt is located in the south-eastern suburbs of Melbourne, and has supplied raw materials to the construction industry for over a hundred years.

CLIENTS

Various sand mine and landfill operators.

BACKGROUND

Unconsolidated sands of the Upper Tertiary “Brighton Group” have been exploited for construction purposes at dozens of locations in suburban Melbourne.

Irregularly distributed “fossilised hydrocarbon” deposits within this formation are associated with ultra fine grained pyrite (framboidal iron-sulphide) mineralisation. Mining in the sand belt often utilises conventional hydraulic extraction and processing methods to recover the quartz-rich sand and separate it from the pore filling carbonaceous and sulphidic material. The sulphidic material is extremely reactive and readily generates highly acid and metalliferous water.

Many of the abandoned opencuts have been used as landfills for municipal waste. The combination of acid generating material, incident rainfall and organic waste has facilitated the production of acidic landfill leachate at many of these waste disposal facilities.

SITE ISSUES

Acidified process water causes substantial damage to the pumps, pipes and affiliated sand processing equipment, and accelerates the ongoing acid generating reactions. In addition, during wet months, excess process water sometimes needs to be released from sites. This water is required to meet statutory discharge standards.

Reducing conditions and elevated nutrients associated with landfills have combined with sulphate-rich acid mine waters to promote the growth of sulphate reducing bacteria. Under acidic to near neutral conditions, these bacteria generate hydrogen sulphide gas causing significant off-site odour concerns.

Bodies of acid water and landfill leachate also have the potential to contaminate local groundwater resources.

No water treatment equipment is available at these sites as the problem of acid water was only identified recently. A Multi Purpose Neutra-Mill provided a low-cost, periodic solution to acid water and associated odour problems as they arose.

WORK PROGRAM

Earth Systems was contracted to examine water quality issues, provide management options and treat polluted water in the Melbourne sand belt, in relation to both sand mining and landfilling activities.

Work programs have included;

• Assessing water quality.
• Developing potential treatment strategies and determining dosing requirements.
• Conducting acid neutralisation and demineralisation treatment programs on process water, storage impoundments and landfill leachate ponds.
• Disinfecting bacterial-rich, acidic landfill leachate for on-site use and off-site disposal.
• Developing programs for controlling off-site noxious gas emissions.

RESULTS

• Instigated routine monitoring strategies for early identification of acid drainage.
• Identified and quantified the nature and scope of acid drainage issues.
• Developed cost-effective acid drainage avoidance and mitigation strategies.
• Predicted the likely economic and environmental consequences of acid drainage generation.
• Successfully treated multiple acid water bodies from 10 megalitres to 200 megalitres with a range of reagents.
• Neutralised acid process water to lower maintenance costs associated with sand processing equipment.
• Lowered suspended solids in turbid and bacterial-rich landfill leachate.
• Treated water to statutory discharge standards for release to the stormwater system.
• Controlled noxious odours from landfill leachate to avoid breaching EPA requirements.