title: Fish populations of Lake Ngaroto, Waikato, and fish passage at the outlet weir.

authors: Hicks, Brendan J.

subjects: Lake Ngaroto

abstract: 1.Lake Ngaroto has a diverse fauna of native and introduced fish. It is largest of the Waipa lakes, is hypertrophic (i.e., has very high concentrations of plant nutrients), and is highly productive for this reason.
2.In an exhaustive fish survey that used gill nets, fyke netx, and beach seining, 4,317 fish of nine species were caught. The catch included five species of introduced fish. Over 70% of the catch was brown bullhead catfish; rudd, goldfish, a single mosquitofish, and a single koi carp were also caught. In summer, mosquitofish numbers a likely to be very high. 
3.Four species of native fish were caught, and of these, shortfinned eels wer the most numerous. Common bullies, a few longfinned eels, and a single common smelt were caught, thought common smelt and common bullies are expected to be much more numerous in summer.
4.The migratory species in the lake are the eels and common smelt. Eels are always migratory, as they spawn in the tropical ocean. Common smelt may be wither migratory or lake-resident, and the single individual caught in this survey had vertebral and gill raker counts diagnostic of a migratory fish. As smelt migrate upstream from the ocean in spring and summer, but are generally absent from freshwaters in winter, the low abundance in August and October 2001 is not surprising.
5.Eels are string migrators, and can climb rock faces and wriggle through small cracks and crevices during their migration. Common smelt migrate by swimming, and high velocities and free-falling water barriers can prevent their upstream passage.
6.We recommend that to all upstream passage of swimming species such as common smelt the rebuilt weir has zones with mean water column velocities no greater than 0.5 m s⁻¹, and preferably 0.3-0.4 m s⁻¹. The length of the downstream slop of the weir should be no more than 4 m, and the water depth over the weir should be at least 5 cm during the time of principal upstream migration (August to December).

text: Fish populations of Lake Ngaroto, Waikato, and fish passage at the outlet weir. 1.Lake Ngaroto has a diverse fauna of native and introduced fish. It is largest of the Waipa lakes, is hypertrophic (i.e., has very high concentrations of plant nutrients), and is highly productive for this reason.
2.In an exhaustive fish survey that used gill nets, fyke netx, and beach seining, 4,317 fish of nine species were caught. The catch included five species of introduced fish. Over 70% of the catch was brown bullhead catfish; rudd, goldfish, a single mosquitofish, and a single koi carp were also caught. In summer, mosquitofish numbers a likely to be very high. 
3.Four species of native fish were caught, and of these, shortfinned eels wer the most numerous. Common bullies, a few longfinned eels, and a single common smelt were caught, thought common smelt and common bullies are expected to be much more numerous in summer.
4.The migratory species in the lake are the eels and common smelt. Eels are always migratory, as they spawn in the tropical ocean. Common smelt may be wither migratory or lake-resident, and the single individual caught in this survey had vertebral and gill raker counts diagnostic of a migratory fish. As smelt migrate upstream from the ocean in spring and summer, but are generally absent from freshwaters in winter, the low abundance in August and October 2001 is not surprising.
5.Eels are string migrators, and can climb rock faces and wriggle through small cracks and crevices during their migration. Common smelt migrate by swimming, and high velocities and free-falling water barriers can prevent their upstream passage.
6.We recommend that to all upstream passage of swimming species such as common smelt the rebuilt weir has zones with mean water column velocities no greater than 0.5 m s⁻¹, and preferably 0.3-0.4 m s⁻¹. The length of the downstream slop of the weir should be no more than 4 m, and the water depth over the weir should be at least 5 cm during the time of principal upstream migration (August to December).

year: 2001

title: Pressure screening studies with wood pulp

authors: Weeds, Zuben

subjects: Wood-pulp Refining Separation

abstract: Pressure screening is used in paper making to separate components of a wood pulp slurry (water, wood fibre and solid contaminant material) and to concentrate the wood fibre. The complex solid-liquid and solid-solid mechanisms involved in pressure screening are still poorly understood. This thesis reviews the literature on pressure screening mechanisms and highlights the problems in the models used to describe pressure screening. 
Two models, based on well-mixed tanks in series, are developed to describe reject thickening behaviour of long and short screens. The first model uses a single one row of tanks to model steady flow from feed to accept and from feed to reject streams of a screen. A back-flow model, which had two rows of well-mixed tanks, one for the feedside and another for the accept-side of the screen, was also developed. The passage ratio for back-flow of fibre PB was estimated numerically by deducing the passage ratio for forward-flow of fibre PF. The model showed that PB can decrease more quickly than PF when feed consistency increases, even when overall passage ratio Pp remains constant. 
A small industrial pressure screen (diameter 203 mm, length 220 mm) was used to investigate the effect of screen length Ls and feed consistency Cf on pressure screening performance. The effects of pulp type ( eucalypt for short fibre and pine kraft pulp for short fibre), feed consistency (from 0.005% to 2% compared to approximately 1 % in industrial plants), screen length and placement along the length of the screen, rotor type (bump or step), and screen hole shape (round holes or slots) were investigated. Measurements of pulp consistency in the feed, reject and accept streams under different processing conditions were used to assess the screen models developed. Screening behaviour of screens less than 220 mm was studied extensively for the first time. 
The tanks-in-series model showed that the effect of screen length on reject thickening could be described as well-mixed tanks in series with plug flow behaviour when the screen was modelled as 100 tanks. The reject thickening factor T decreased semilogarithmically when number of tanks was decreased but increased slightly when the number of tanks was increased. . Reject thickening factor decreases when a screen with 1-mm hole is shortened from 220 mm to 27 mm. This reduction can be attributed mainly to the flow regime changing from plug to mixed flow.
The maximum volumetric accept flow rate Qmax decreased by approximately 30 % when a 55-mm screen section was moved from the feed end to the reject end. 1bis decrease in Qmax was consistent with an axial decrease in relative speed ( difference between rotor tip and pulp suspension in the feed annulus), along with an estimated 33% reduction in the negative pressure pulse PNP along the screen. Overall fibre passage ratio PP also decreased when the screen section was moved to the reject end, or when pulp was accelerated in a feed chamber upstream of the feed annulus. 
The three distinct regions and two critical feed consistencies observed when Cr increased from 0.005% to 2% are postulated to indicate when fibre accumulation on the feed and accept sides of the screen produces screen plugging. The critical Cr for the accept side is about ten times greater than that for the feed side due mainly to the fact that the conical holes have a larger diameter on the accept side so more fibre must accumulate before backflow is hindered. In Region 1 ( crowding number < 1 ), reject thickening is independent of feed consistency and remains constant regardless of rotor type (bump or step) and screen type (smooth holes or contoured slots). In Region 2 (1< crowding number< 60), reject thickening decreases with feed consistency. In Region 3 (crowding number > 60), reject thickening either . decreases with feed consistency or remains constant depending on the ratio of forward to back-flushing flow exhibited by the rotor and as predicted by the two-tanks in series model. For the step rotor with a flow ratio of 2:1 reject thickening is constant with feed consistency regardless of screen type. For the bump rotor with a flow ratio of 5: 1 reject thickening decreases with feed consistency regardless of the screen type.
Fibre-length fractionation index <I> increased with increasing Cr to a maximum at about Ct=0.7% when using a 1-mm smooth-holed screen with a bump rotor or at Ct=2% for a 2.4-mm smooth-holed screen. Fractionation index then decreased with increasing Cf. 
It is recommended that the back-flow model be further developed so that the volumetric flow ratio (ratio of forward flow to back flow) can be calculated from a residence time distribution. It is also recommended that fibre-length fractionation be attempted at various positions along the screen for medium consistency pulp (Cr of 8 to 12%) using unconventionally large holes (3-5 mm).

text: Pressure screening studies with wood pulp Pressure screening is used in paper making to separate components of a wood pulp slurry (water, wood fibre and solid contaminant material) and to concentrate the wood fibre. The complex solid-liquid and solid-solid mechanisms involved in pressure screening are still poorly understood. This thesis reviews the literature on pressure screening mechanisms and highlights the problems in the models used to describe pressure screening. 
Two models, based on well-mixed tanks in series, are developed to describe reject thickening behaviour of long and short screens. The first model uses a single one row of tanks to model steady flow from feed to accept and from feed to reject streams of a screen. A back-flow model, which had two rows of well-mixed tanks, one for the feedside and another for the accept-side of the screen, was also developed. The passage ratio for back-flow of fibre PB was estimated numerically by deducing the passage ratio for forward-flow of fibre PF. The model showed that PB can decrease more quickly than PF when feed consistency increases, even when overall passage ratio Pp remains constant. 
A small industrial pressure screen (diameter 203 mm, length 220 mm) was used to investigate the effect of screen length Ls and feed consistency Cf on pressure screening performance. The effects of pulp type ( eucalypt for short fibre and pine kraft pulp for short fibre), feed consistency (from 0.005% to 2% compared to approximately 1 % in industrial plants), screen length and placement along the length of the screen, rotor type (bump or step), and screen hole shape (round holes or slots) were investigated. Measurements of pulp consistency in the feed, reject and accept streams under different processing conditions were used to assess the screen models developed. Screening behaviour of screens less than 220 mm was studied extensively for the first time. 
The tanks-in-series model showed that the effect of screen length on reject thickening could be described as well-mixed tanks in series with plug flow behaviour when the screen was modelled as 100 tanks. The reject thickening factor T decreased semilogarithmically when number of tanks was decreased but increased slightly when the number of tanks was increased. . Reject thickening factor decreases when a screen with 1-mm hole is shortened from 220 mm to 27 mm. This reduction can be attributed mainly to the flow regime changing from plug to mixed flow.
The maximum volumetric accept flow rate Qmax decreased by approximately 30 % when a 55-mm screen section was moved from the feed end to the reject end. 1bis decrease in Qmax was consistent with an axial decrease in relative speed ( difference between rotor tip and pulp suspension in the feed annulus), along with an estimated 33% reduction in the negative pressure pulse PNP along the screen. Overall fibre passage ratio PP also decreased when the screen section was moved to the reject end, or when pulp was accelerated in a feed chamber upstream of the feed annulus. 
The three distinct regions and two critical feed consistencies observed when Cr increased from 0.005% to 2% are postulated to indicate when fibre accumulation on the feed and accept sides of the screen produces screen plugging. The critical Cr for the accept side is about ten times greater than that for the feed side due mainly to the fact that the conical holes have a larger diameter on the accept side so more fibre must accumulate before backflow is hindered. In Region 1 ( crowding number < 1 ), reject thickening is independent of feed consistency and remains constant regardless of rotor type (bump or step) and screen type (smooth holes or contoured slots). In Region 2 (1< crowding number< 60), reject thickening decreases with feed consistency. In Region 3 (crowding number > 60), reject thickening either . decreases with feed consistency or remains constant depending on the ratio of forward to back-flushing flow exhibited by the rotor and as predicted by the two-tanks in series model. For the step rotor with a flow ratio of 2:1 reject thickening is constant with feed consistency regardless of screen type. For the bump rotor with a flow ratio of 5: 1 reject thickening decreases with feed consistency regardless of the screen type.
Fibre-length fractionation index <I> increased with increasing Cr to a maximum at about Ct=0.7% when using a 1-mm smooth-holed screen with a bump rotor or at Ct=2% for a 2.4-mm smooth-holed screen. Fractionation index then decreased with increasing Cf. 
It is recommended that the back-flow model be further developed so that the volumetric flow ratio (ratio of forward flow to back flow) can be calculated from a residence time distribution. It is also recommended that fibre-length fractionation be attempted at various positions along the screen for medium consistency pulp (Cr of 8 to 12%) using unconventionally large holes (3-5 mm).

year: 2006

title: Haumanu Hauora: refining public health institution policy to include Māori and climate change

authors: Masters-Awatere, Bridgette

abstract: The deepening climate crisis generates specific impacts that will exacerbate the already disproportionately negative health outcomes experienced by Indigenous people. Disparate health outcomes have not spontaneously emerged, but rather have been foreshadowed by existing inequities. This article summarizes a sample of the work from a two-year research project in Aotearoa New Zealand to understand existing policy processes and ascertain the extent to which health institutions give serious consideration to climate change impacts on Māori (Indigenous people) with health vulnerabilities. Speaking to tāngata whenua (Indigenous Māori), District Health Board (DHB) employees, and subject matter experts (SMEs), it was clear that policy processes were ad hoc and problematically silenced consistent Māori input. While research participants expressed their experiences of, and aspirations for, dealing with climate change, their voices were not evident in DHB policy development processes. The deficit within existing policy process reflects a lack of preparedness in the face of climate change. Despite clear resilience and adaptation strategies, structural change is needed to address identified disadvantages. Through a co-designed policy framework (“Haumanu Hauora”), we guide policy formation to mitigate climate change risk to Māori (and others). Central to the revised policy framework is the creation of space for both internal and external Māori voices to ensure consistent Māori input throughout the policy process. We also introduce a commissioning, refining, and monitoring stage (that includes evaluation). Haumanu Hauora considers whānau-centered healthcare knowledge, needs, resources, and aspirations, to contribute to a transformed and responsive health system. Above all, we believe that strengthening health institution responsiveness to Māori health needs is essential.

text: Haumanu Hauora: refining public health institution policy to include Māori and climate change The deepening climate crisis generates specific impacts that will exacerbate the already disproportionately negative health outcomes experienced by Indigenous people. Disparate health outcomes have not spontaneously emerged, but rather have been foreshadowed by existing inequities. This article summarizes a sample of the work from a two-year research project in Aotearoa New Zealand to understand existing policy processes and ascertain the extent to which health institutions give serious consideration to climate change impacts on Māori (Indigenous people) with health vulnerabilities. Speaking to tāngata whenua (Indigenous Māori), District Health Board (DHB) employees, and subject matter experts (SMEs), it was clear that policy processes were ad hoc and problematically silenced consistent Māori input. While research participants expressed their experiences of, and aspirations for, dealing with climate change, their voices were not evident in DHB policy development processes. The deficit within existing policy process reflects a lack of preparedness in the face of climate change. Despite clear resilience and adaptation strategies, structural change is needed to address identified disadvantages. Through a co-designed policy framework (“Haumanu Hauora”), we guide policy formation to mitigate climate change risk to Māori (and others). Central to the revised policy framework is the creation of space for both internal and external Māori voices to ensure consistent Māori input throughout the policy process. We also introduce a commissioning, refining, and monitoring stage (that includes evaluation). Haumanu Hauora considers whānau-centered healthcare knowledge, needs, resources, and aspirations, to contribute to a transformed and responsive health system. Above all, we believe that strengthening health institution responsiveness to Māori health needs is essential.

year: 2023-05-05