DEMM Engineering & Manufacturing
How to handle wastewater with low environmental and energy impacts
One of Australia's most remote and environmentally aware local authorities will open an Australian- engineered wastewater treatment plant this month that cuts maintenance, energy demands and OH&S issues.
The cost- efficient wastewater treatment system is currently being assembled (first half of 2018) by Australian company CST Wastewater Solutions for installation on World- Heritage listed Lord Howe Island in the second half of the year, to replace the existing waste management facility on the Island, 900 km off the coast of Eastern Australia.
The two-stage system–suitable for smaller, remote and ecologically sensitive community, municipal, agribusiness and industrial applications – was selected by the Island Board of Lord Howe after extensive testing to determine the best solution for the management and disposal of waste generated on the island.
“It uses a combination of coarse and fine screening and advanced dry compaction KDS separator technology to produce a more hygienic and more compact output that is easier to handle and transport. The system is more economical, compact and uses less energy and minimal water compared to alternative systems,” says CST Wastewater Solutions’ Managing Director, Michael Bambridge.
Japanese-manufactured and Australian-engineered KDS systems–for which CST Wastewater Solutions is exclusive distributor
– are being introduced to the Asia- Pacific for compact dewatering applications ranging from food processing, food waste, grease trap and waste oil through to municipal wastewater sludge, livestock manure and agribusiness processes.
ADVANCED GRIT REMOVAL
CST also distributes the Smith & Loveless PISTA 360 fine screening technology, which removes 95 percent of grit as small as 105 microns (140 mesh).
The technology sets an entirely new benchmark for grit removal, which has t ypically been set at 95 percent as small as 250 microns, says Bambridge.
The technology also:
• Reduces the enormous cost of de- sanding downstream aeration basins, channels and digestors.
• Reduces damage to downstream equipment from wear.
• Eliminates the loss of efficiency of downstream processes through loss of active volume.
• Enhances Waste Water Treatment
Plant reliability.
• Reduces OH&S hazards involved in unclogging systems.
• Helps to prevent environmental spills from blocked and f looded systems.
WASTE STREAMS
The existing waste management facility for Lord Howe Island sorts various waste streams including food waste, paper and cardboard, green waste, recyclable materials re- usable materials and general waste. Septic Waste from the residential and commercial system is also treated at this facility, drawn from about 220 wastewater systems on the island, 25 of which are commercial operations. Currently pumpouts are delivered to the facility via a 1,800 litre wastewater tanker.
CST Wastewater Solutions was tasked by the Lord Howe Island Board to review a “best fit” sludge dewatering system for the septic waste, because the current infrastructure is becoming outdated and the existing drying beds are to be decommissioned. Working with Lord Howe Island Board’s Project Manager, CST Wastewater Solutions developed an optimal solution that combined outstanding environmental performance with equally strong OHS performance – and which has a much smaller footprint than the drying rack system used currently, says CST.
CST’s new t wo stage system comprises:
1. The first stage is a CST Screen Extractor with coarse screening at 6.0mm up front to remove plastic, rags and other disposals t ypically found in community, commercial and industrial waste water treatment plants.
2. The second stage employed CST’s new KDS Separator technology for fine screening and dewatering of the fines. The KDS system was developed in Japan, a country which is highly focused on food and water purity. CST Wastewater Solutions engineers KDS’ latest technologies into Australian- engineered packages specified to achieve best results in individual locations, such as Lord Howe Island.
The compact KDS multi- disc roller separator features a unique self- cleaning dewatering and conveying system with oval plate separation and transfer structure that prevents clogging and permits automatic continuous operation that handles oily and fibrous material with ease.
“This simple-to- maintain separator offers a high throughput within a small body, with the smallest model being just under 350mm wide and weighing 50 kg. It is ideal for applications such as Lord Howe Island and other smaller communities and industrial applications throughout the AsiaPacific, including coastal, remote and ecologically sensitive areas. It is more hygienic and produces an output that is twice as light and half the cost to transport for disposal, compared to other systems. It is also extremely compact, energy efficient and uses minimal water,” says Bainbridge.
Designed for efficiency, sustainability and conservation of resources in small-to- medium applications, the energy- efficient KDS separator consumes as lit tle as 0.06kW hr of electricity and uses no wash water. Compared to alternate technologies it saves on power, space and money, he says.
“The KDS separator uses a fraction of the power of a centrifuge and involves no water usage during operation, unlike a belt press or a screw press. For a relatively low investment cost, it offers a high- performance alternative for example to sludge drying beds and geobags.”
The KDS technology can also be used for thickening of dissolved air f lotation sludge – a very common application throughout waste water operations – in which role it achieves solids capture of 97 percent thickened sludge at a dryness of 17 percent. Waste activated sludge dryness levels are t ypically 15-25 percent.
The compact rotational oval plate structure achieves high transportation and separation efficiencies, while the simplicity of the machine’s overall structure offers low maintenance, achieving cost and OH&S benefits through less handling being required to clear hazardous materials.
The ‘unique’ self- cleaning action of the KDS separator, which is available in hydraulic capacities from 264- 4092 gal/ hr (approx. 1000-15490 litres) with input solids content of t wo percent
Applications for which the separator is designed:
• Food processing waste, including snackfoods, kitchen and restaurant waste, raw wastewater ( primary screening) and sludge.
• Sewage treatment, including raw wastewater ( primary screening) and sludge to landfill.
• Abattoir, feedlots, and dairy farm wastewater and sludge. Cattle manure cake dryness of 25- 35 percent is t ypically achieved.
• Pig farm raw manure and sludge, with cake dryness of 20- 30 percent.
• Barrel polishing water, water- based paint wastewater, grease trap waste, dyeing wastewater, waste oil, and plastic recycling.
• Seafood processing.