Attachments 11.4 and 11.5 - City of Busselton

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ATTACHMENT C - TREATMENT OPTIONS CONSIDERED IN THE COUNCILLOR WORKSHOP OF MAY 2011 ITEM 11.4 COUNCIL 12/10/2011 2 Another approach completely is to physically sink the algae to the bottom of the river through the use of flocculating clays and other materials. In fact one such trial of a prospective material has already been trialled on the LVR. These methods rely on the added material to bind together the algal cells so that they become heavier and sink. Much work has been conducted overseas mainly on dinoflagellate phytoplankton and relatively little on blue green algae which are the main LVR Phytoplankton type. Research in China has shown that Loess clays can remove algae and that clays mixed with Chitonase are especially effective. Chitonase is a natural product made from ground up mollusc shells. All of these products only remove algae from the surface to the bottom. However when the algal cells breakdown the nutrient is released and again becomes available for algal growth. This treatment therefore also needs to be used in conjunction with another product, such as Phoslock, that binds the phosphorous so it is not available. Chitonase is currently quite expensive. The price has been driven up by it’s medicinal uses. Algal removal for the LVR Another approach is to physically remove the algae from the river which is difficult given the buoyant nature of the blue greens involved. During the Jan 2000 algal bloom in the Swan suction trucks were effectively used to remove algae, which was then transported to a Water corporation Waste water treatment facility. The technique works because the buoyant algae floats to the surface in the vacuum truck and the algae clear water can be decanted from the bottom which reduces the number of truck journeys required. The disadvantage is that once the algae is removed more will grow due to the abundant supply of phosphorus and so treatments of Phoslock would also be required. The advantage of physical removal is that both nutrients and organic sludge are removed from the system. This option has not been costed and would depend on disposal at Water Corporation site and availability of vacuum trucks. Nutrisorb Nutrisorb is a by-product of the mineral sands industry produced by Iluka. It has very good physical filtration properties and therefore is thought to be a good treatment to use within the catchment close to the source of the pollutants. For example, it could be used as a soil amendment around point sources such as dairy effluent ponds and paddocks where the effluent is disposed of, or diffuse sources such as paddocks as a top dressing which prevents nutrients from getting into creek lines.
ATTACHMENT C - TREATMENT OPTIONS CONSIDERED IN THE COUNCILLOR WORKSHOP OF MAY 2011 ITEM 11.4 COUNCIL 12/10/2011 3 Use of nutrisorb to filter nutrients from the lower Vasse River in situ would require costly engineering processes to recirculate the water through pumps, filters and pipes and replace the filter medium on a regular basis as it became saturated. As this is not the intended application for this material it is not a good option for treatment of the Lower Vasse River. Bio-filtration Bio-filtration is the same process that is used for water Quality improvement of stormwater. The suggestion is that perhaps some of the bio-filtration basins that have been constructed for treatment of stormwater before it gets into the river in winter could be used for recirculation of the river water during summer. Bio-filtration uses soils and plants to take up the nutrients. Water entering the system is allowed to pass through the soil and plant roots giving them the opportunity to take up the nutrients. The soil medium takes most of the Phosphorous while the plants take out most of the Nitrogen. Excess water that is not transpired by the plants passes out the bottom of the system and back into the river. Periodically the plants need to be harvested and the soil medium replaced to remove the nutrients from the system. The constructed wetland at the end of Bunbury Street in the LIA has only recently been installed and will be monitored for its effectiveness to remove nutrient from winter run-off. The potential to treat water from the river during summer should be investigated. Macrophytes Submerged macrophytes have an important role in maintaining water clarity in wetland systems, and at low levels of nutrient enrichment, their presence can prevent a shift to a turbid, phytoplankton-dominated state (Scheffer, 2004). There has been much research regarding the mechanisms by which macrophyte maintain a clear-water state, which include: • enhanced top-down control of phytoplankton by grazing zooplankton; • sediment trapping and reduced resuspension; • alterations to nutrient cycling and availability, including competition with phytoplankton; • shading; and • possible effects of allelopathy. (Søndergaard and Moss, 1998; Stephen et al., 1998; Jeppesen et al., 1999). Despite their important role, there has been little research into the benefits of macrophyte restoration. Restoration of macrophytes is difficult in nutrient-enriched systems due to light limitations caused by dense growth of phytoplankton and epiphytes. Previous research in the Lower Vasse River has demonstrated that the submerged macrophyte Vallisneria australis can be grown successfully in
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LAND inSights ATTACHMENT A - DRAFT
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CA V ES R D BU SE LH WY CA V ES R D
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CA V E S R D CA V E S R D AL B E R
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ATTACHMENT A - DRAFT LEPS ITEM 11.5
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SUES RD VASSE ATTACHMENT A - DRAFT
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MEELUP BEACH RD CASTLE R O C K RD A
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CA V E S R D CA V E S R D AL B E R
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SUMMARY OF SUBMISSIONS PROPOSAL: Lo
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Attachments 11.4 and 11.5 - City of Busselton

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