title: Studies of modified pumice and titanomagnetite filtration media

authors: Yang, Zailu

abstract: There is a continuing interest in filtration technologies capable of more efficient filtration, particularly of small microbial particles, but which place less reliance on the use of water treatment chemicals. In order to develop new options for granular filtration systems, two indigenous New Zealand media, titanomagnetite (TM) and pumice were investigated. TM was of interest because its particle size is finer than most filtration media and its magnetic properties allow the possibility of magnetic conditioning of the bed. A modified pumice, marketed as Silicon Sponge (SS), is already finding application in filtration systems where its low effective density and porous structure make it ideally suited for use as the upper layer of dual media filters. 

Particle size and surface charge are key parameters influencing the effectiveness of a given filtration medium. Finer medium particle size improves filtration efficiency but at the expense of lower hydraulic conductivity. Magnetic conditioning of fine TM filtration beds was used to improve hydraulic conductivity. Hydraulic conductivity was increased by 140% when a vertically aligned magnetic field 0.018 T was applied. However filtration efficiency was decreased by about 9% in the conditioned (expanded) bed. Adjustment of pH to enhance electrostatic interactions more than compensated for this decrease. 

The particulate matter of most waters requiring filtration is negatively charged. Surface treatment to make a filtration medium more electropositive is known to improve the medium’s filtration effectiveness. The isoelectric point (IEP) of natural TM, even after rigorous chemical cleaning, was found to be 3.64 ± 0.06 This value was confirmed by the preparation of a synthetic TM and the measurement of its IEP. Attempts to raise the IEP of natural TM by treatment with aluminium and iron polycation solutions were unsuccessful. 

Greater success was achieved in the modification of the properties of SS by treatment with aluminium and iron polycation solutions and mixtures of these solutions. IEPs ranging from the 4.10 ± 0.06 of acid rinsed SS to the 8.52 ± 0.06 of aluminium treated SS were achieved. In addition, it was found possible to impart magnetic properties to fine SS by the use of treatment solutions containing a mixture of ferric and ferrous ions. The presence of aluminium in the treatment solutions allowed higher IEPs to be obtained but the magnetic effect was reduced. In the absence of aluminium, the ferric/ferrous mixture gave a product with a magnetic effect that was 7% of that observed for pure magnetite. 

Filtration studies using 1.7 μm negatively charged kaolin as a model negative colloid showed that significant increases in filtration efficiency were achieved by medium pre-treatments with the aluminium and iron solutions. For example, turbidity removal for 710-1000 μm SS was increased from 22% to 94% by aluminium pre-treatment. 

The information on the performance of magnetically conditioned beds and the ability to enhance filtration efficiency by surface modification using iron and aluminium has potential applications in the design of novel systems for water and wastewater treatment. A small-scale system based upon the use of a permanent magnet has been proposed and work in this area is continuing.

text: Studies of modified pumice and titanomagnetite filtration media There is a continuing interest in filtration technologies capable of more efficient filtration, particularly of small microbial particles, but which place less reliance on the use of water treatment chemicals. In order to develop new options for granular filtration systems, two indigenous New Zealand media, titanomagnetite (TM) and pumice were investigated. TM was of interest because its particle size is finer than most filtration media and its magnetic properties allow the possibility of magnetic conditioning of the bed. A modified pumice, marketed as Silicon Sponge (SS), is already finding application in filtration systems where its low effective density and porous structure make it ideally suited for use as the upper layer of dual media filters. 

Particle size and surface charge are key parameters influencing the effectiveness of a given filtration medium. Finer medium particle size improves filtration efficiency but at the expense of lower hydraulic conductivity. Magnetic conditioning of fine TM filtration beds was used to improve hydraulic conductivity. Hydraulic conductivity was increased by 140% when a vertically aligned magnetic field 0.018 T was applied. However filtration efficiency was decreased by about 9% in the conditioned (expanded) bed. Adjustment of pH to enhance electrostatic interactions more than compensated for this decrease. 

The particulate matter of most waters requiring filtration is negatively charged. Surface treatment to make a filtration medium more electropositive is known to improve the medium’s filtration effectiveness. The isoelectric point (IEP) of natural TM, even after rigorous chemical cleaning, was found to be 3.64 ± 0.06 This value was confirmed by the preparation of a synthetic TM and the measurement of its IEP. Attempts to raise the IEP of natural TM by treatment with aluminium and iron polycation solutions were unsuccessful. 

Greater success was achieved in the modification of the properties of SS by treatment with aluminium and iron polycation solutions and mixtures of these solutions. IEPs ranging from the 4.10 ± 0.06 of acid rinsed SS to the 8.52 ± 0.06 of aluminium treated SS were achieved. In addition, it was found possible to impart magnetic properties to fine SS by the use of treatment solutions containing a mixture of ferric and ferrous ions. The presence of aluminium in the treatment solutions allowed higher IEPs to be obtained but the magnetic effect was reduced. In the absence of aluminium, the ferric/ferrous mixture gave a product with a magnetic effect that was 7% of that observed for pure magnetite. 

Filtration studies using 1.7 μm negatively charged kaolin as a model negative colloid showed that significant increases in filtration efficiency were achieved by medium pre-treatments with the aluminium and iron solutions. For example, turbidity removal for 710-1000 μm SS was increased from 22% to 94% by aluminium pre-treatment. 

The information on the performance of magnetically conditioned beds and the ability to enhance filtration efficiency by surface modification using iron and aluminium has potential applications in the design of novel systems for water and wastewater treatment. A small-scale system based upon the use of a permanent magnet has been proposed and work in this area is continuing.

year: 2001

title: Characterisation of a thermostable pepstatin-insensitive acid proteinase from a Bacillus sp.

authors: Prescott, Mark

subjects: acid proteinase

abstract: An acid proteinase, Wai 21a, produced by a thermophilic Bacillus species (strain Wai 21a) has been purified to homogeneity by cation-exchange chromatography, phenyl-Sepharose chromatography and anion-exchange chromatography. A pI of 3.8 was determined by isoelectric focussing. The protein contained some associated carbohydrate (20 mol hexose equiv/mol proteinase). Optimal proteolytic activity was observed at pH 3.0 (at 60°C). The Leu¹⁵-Tyr¹⁶ bond was the major site of hydrolysis for the oxidized B chain of insulin. Enzyme activity was not affected by inhibitors of the cysteine, metallo or serine class of proteinases. The aspartate proteinase inhibitor, pepstatin, did not inhibit enzyme activity. Inhibition of enzyme activity by 1,2-epoxy-3-(p-nitrophenoxy)-propane indicated the presence of at least one carboxyl group essential to the catalytic mechanism of the enzyme. Proteinase activity was inhibited by diazoacetyl-  -norleucine methyl ester in a slow and non-specific manner atypical of pepstatin-sensitive aspartate proteinases. Wai 21a proteinase may be classified as member of the pepstatin-insensitive group of aspartate proteinases. The thermal stability at pH 3.0 and 60°C increased 2.1-fold (t1/2, 4.5–9.7 hr) in the presence of 5 mM Ca⁺⁺. An increase in both pH (3.0–4.5) and Ca⁺⁺ concentration (0–30 mM) resulted in a 15-fold increase (t1/2, 15–230 min) in thermal stability at 75°C. The amino acid composition of Wai 21a proteinase was found to be similar to other pepstatin-insensitive proteinases from bacterial sources and in particular similar to the thermostable enzyme, kumamolysin.

text: Characterisation of a thermostable pepstatin-insensitive acid proteinase from a Bacillus sp. An acid proteinase, Wai 21a, produced by a thermophilic Bacillus species (strain Wai 21a) has been purified to homogeneity by cation-exchange chromatography, phenyl-Sepharose chromatography and anion-exchange chromatography. A pI of 3.8 was determined by isoelectric focussing. The protein contained some associated carbohydrate (20 mol hexose equiv/mol proteinase). Optimal proteolytic activity was observed at pH 3.0 (at 60°C). The Leu¹⁵-Tyr¹⁶ bond was the major site of hydrolysis for the oxidized B chain of insulin. Enzyme activity was not affected by inhibitors of the cysteine, metallo or serine class of proteinases. The aspartate proteinase inhibitor, pepstatin, did not inhibit enzyme activity. Inhibition of enzyme activity by 1,2-epoxy-3-(p-nitrophenoxy)-propane indicated the presence of at least one carboxyl group essential to the catalytic mechanism of the enzyme. Proteinase activity was inhibited by diazoacetyl-  -norleucine methyl ester in a slow and non-specific manner atypical of pepstatin-sensitive aspartate proteinases. Wai 21a proteinase may be classified as member of the pepstatin-insensitive group of aspartate proteinases. The thermal stability at pH 3.0 and 60°C increased 2.1-fold (t1/2, 4.5–9.7 hr) in the presence of 5 mM Ca⁺⁺. An increase in both pH (3.0–4.5) and Ca⁺⁺ concentration (0–30 mM) resulted in a 15-fold increase (t1/2, 15–230 min) in thermal stability at 75°C. The amino acid composition of Wai 21a proteinase was found to be similar to other pepstatin-insensitive proteinases from bacterial sources and in particular similar to the thermostable enzyme, kumamolysin.

year: 1995

title: Kua Huri Taku Tira: The Rereahu Journey Towards Autonomy

authors: Crown, Jenny

subjects: autonomy

abstract: The establishment of the Native Land Court in Aotearoa New Zealand by the settler government caused much upheaval for tangata whenua. Traditional land tenure was interrupted by the colonised view of land ownership. Impetus to establish individual ownership of land was placed upon iwi and hapū Māori. This necessitated the iwi and hapū of the Rohe Pōtae to define their own individual boundaries within the autonomous region.

Over one hundred years later, the New Zealand government were under pressure from the Māori community. Iwi and hapū were vociferous in their requirements. The returning of land and natural resources to Māori was of paramount importance. The implementation of the Māori Trust Board Act enabled iwi and hapū to establish governance entities which permitted access to government funding. These entities also provided a vehicle through which iwi could pursue cultural redress from the Crown. This was the only way forward – the way dictated by the Crown.

Devolution was to become a reality and a sign of the decolonisation process at play. Such would allow Māori to re-establish autonomy which had been lost over a century prior. Destructive notions such as marginalisation, disenfranchisement and displacement would be reversed and Māori would regain control over their own cultural practices, cultural resources and future. Under the Fourth Labour Government of New Zealand this became a reality for some iwi and hapū.

This thesis investigates the attempts made by the Rereahu iwi in securing such recognition. Interrogation into the many ways in which Rereahu has attempted to navigate the multiple political landscapes which still exist and continue to control iwi and hapū have been discussed. The study develops a theoretical framework of Māori wide concepts as applied through a Rereahu-centric lens. Thus, allowing for a balanced approach to the collection, collation and analysis of all evidence utilised in this thesis.

Key findings bring to light the effects colonisation has had and continues to have on Rereahu autonomy. The ways in which Rereahu has been misrepresented, and how Rereahu has responded to threats of colonisation in the 21st century are apparent. This thesis contributes new knowledge to the realm of academia through the experiences of the iwi Rereahu; and offers indigenous discourse regarding resilience and resistance.

The ongoing effects of colonisation being felt by the Rereahu iwi in this contemporary landscape are defined. It is an example of how the oppressed can easily become the oppressor. This thesis goes some way to highlighting the destructive nature of the Waitangi Tribunal process in regards to Rereahu. The knowledge presented in this thesis could be utilised by the Office of Treaty Settlements, education and health establishments, policy makers and the iwi of Rereahu in addressing and combating the negative effects created by the cycle of colonisation.

text: Kua Huri Taku Tira: The Rereahu Journey Towards Autonomy The establishment of the Native Land Court in Aotearoa New Zealand by the settler government caused much upheaval for tangata whenua. Traditional land tenure was interrupted by the colonised view of land ownership. Impetus to establish individual ownership of land was placed upon iwi and hapū Māori. This necessitated the iwi and hapū of the Rohe Pōtae to define their own individual boundaries within the autonomous region.

Over one hundred years later, the New Zealand government were under pressure from the Māori community. Iwi and hapū were vociferous in their requirements. The returning of land and natural resources to Māori was of paramount importance. The implementation of the Māori Trust Board Act enabled iwi and hapū to establish governance entities which permitted access to government funding. These entities also provided a vehicle through which iwi could pursue cultural redress from the Crown. This was the only way forward – the way dictated by the Crown.

Devolution was to become a reality and a sign of the decolonisation process at play. Such would allow Māori to re-establish autonomy which had been lost over a century prior. Destructive notions such as marginalisation, disenfranchisement and displacement would be reversed and Māori would regain control over their own cultural practices, cultural resources and future. Under the Fourth Labour Government of New Zealand this became a reality for some iwi and hapū.

This thesis investigates the attempts made by the Rereahu iwi in securing such recognition. Interrogation into the many ways in which Rereahu has attempted to navigate the multiple political landscapes which still exist and continue to control iwi and hapū have been discussed. The study develops a theoretical framework of Māori wide concepts as applied through a Rereahu-centric lens. Thus, allowing for a balanced approach to the collection, collation and analysis of all evidence utilised in this thesis.

Key findings bring to light the effects colonisation has had and continues to have on Rereahu autonomy. The ways in which Rereahu has been misrepresented, and how Rereahu has responded to threats of colonisation in the 21st century are apparent. This thesis contributes new knowledge to the realm of academia through the experiences of the iwi Rereahu; and offers indigenous discourse regarding resilience and resistance.

The ongoing effects of colonisation being felt by the Rereahu iwi in this contemporary landscape are defined. It is an example of how the oppressed can easily become the oppressor. This thesis goes some way to highlighting the destructive nature of the Waitangi Tribunal process in regards to Rereahu. The knowledge presented in this thesis could be utilised by the Office of Treaty Settlements, education and health establishments, policy makers and the iwi of Rereahu in addressing and combating the negative effects created by the cycle of colonisation.

year: 2019