Case Study

Anaerobic Treatment of High-Strength Wastewaters

The Watsonia meat-processing factory at Spearwood in Western Australia produced high BOD and COD wastewaters. A suitable process was required to treat the wastewater before discharge to the sewer.

Solution

The effluent from the meat-processing factory now is treated in a Hybractor--a hybrid, high-rate anaerobic reactor for the treatment of medium- to high-strength industrial wastewater. It has the added benefit of producing methane.

Hybrid reactors combine the best features of suspended-bed and fixed-film technologies in one unit and comprise a(n)rotary screen for the removal of course material prior to equalization; equalization tank; anaerobic reactor tank for the production of methane gas;induced air flotation (IAF) cell for the removal of refined solids sludge solids tank; belt press for dewatering sludge; methane storage bag; and anaerobic bacteria, supported on a biofilm, to convert organic pollutants into methane and carbon dioxide.

The unit is designed to:

  • treat a wide range of waste strengths, composition, and volumes;
  • reduce power and wastewater discharge costs;
  • provide an energy credit by generating methane gas;
  • minimize hydraulic retention time (less than 20 hours);
  • use small reactors, keeping capital costs low;
  • have few moving parts, minimizing blockages--allowing low-operating and -maintenance costs
  • rapidly reach peak performance;
  • resist shock loads;
  • rapidly restart after shutdown; and
  • produce minimal sludge and odor.

Performance Characteristics

The Spearwood plant, has a feed flow of about 30 kL/hr at strengths of
BOD (total): 1200 to 2000mg/L.
BOD (soluble): 500 to 1000mg/L.
TSS: 800 to 2000 mg/L
oil & grease: 200 to 500mg/L.

Its output is
BOD (total): 100 to 300 mg/L
BOD (soluble): 40 to 100 mg/L
TSS: 100 to 300mg/L
oil & grease: 20 to 100 mg/L

Its other operating results include
biogas production: 600 to 1200m3/day;
biogas methane: 78 to 82%;
overall power consumption: 1.1 to 12kWh/kL; net operating cost: AUS$0.10 to 0.15/kL (including labor, power, chemicals, maintenance, and biogas credit); and total capital cost: $2.5 million.

For more information about this case study contact Lance Heath, manager, Technology Diffusion Services, Environment Industry Development Network, PO Box 237 Civic Square Act 2608, Australia. Tel: +61.2.6247.2860; E-mail: lheath@ibm.net.