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The effects of Electromagnetism on potable water and waste water has been proven in practice but not scientifically proven to the extent that it is accepted by Engineers and Engineering Consultants. The operating principle of magnetic filtration or separation is based on the interaction of electromagnetic fields with the materials under test. Technical water system (TWS) system configuration has been analysed to determine the system characteristics. Three field trials and some laboratory experiments have been reported in this report. Finite element software has been used for the analysis of magnetic field distribution of the TWS system and also for magnetic separation modelling. There is a need to do some more experiments for more convincing and conclusive outcome.

Geysers that discharge water and steam intermittently to the atmosphere are one of the rarest natural phenomena associated with geothermal systems. Several approaches including laboratory experiments, field observations and mathematical and numerical modelling studies are used in the present study to explain the behaviour of geysers and the important parameters controlling the eruption of geysers. A particular study is made of three geysers at Rotorua geothermal field: Pohutu, Prince of Wales Feathers and Waikorohihi. The existing mathematical model (steinberg et al., 1981a) is studied and an improved mathematical model is developed to accommodate two-phase flow and the variation in fluid properties with temperature. Both the existing and the improved mathematical models are used to model Pohutu and are able to reproduce not only the interval between eruptions but also the durations of the cavern filling and the duration of the pre-play stage observed by the author on the 20th of August 1993. Fully transient numerical models, which include the eruption process itself, are developed using MULKOM and the AUTOUGH2 simulators and produce reasonably good agreement with the analytical solutions and experimental data. The model provides information about the processes inside the geyser system and models the surface discharge which cannot be modelled using the Steinberg type of model. A fully transient model for Pohutu, which is developed using the AUTOUGH2 simulator, is able to reproduce the behaviour observed by the author on the 20th of August 1993. The results of sensitivity studies show that of the three Rotorua geysers, the Feathers is the most sensitive to changes in the rate of the hot upflow from depths. Both the Feathers and Waikorohihi are more sensitive to temperature changes than Pohutu. Pohutu is currently a vigorous geyser with preliminary pulsating spring behaviour; large changes in the rate and temperature of the hot upflow would be required to stop it erupting. All geysers are sensitive to variations in the water level and temperature in Te Horu.

Geysers that discharge water and steam intermittently to the atmosphere are one of the rarest natural phenomena associated with geothermal systems. Several approaches including laboratory experiments, field observations and mathematical and numerical modelling studies are used in the present study to explain the behaviour of geysers and the important parameters controlling the eruption of geysers. A particular study is made of three geysers at Rotorua geothermal field: Pohutu, Prince of Wales Feathers and Waikorohihi. The existing mathematical model (steinberg et al., 1981a) is studied and an improved mathematical model is developed to accommodate two-phase flow and the variation in fluid properties with temperature. Both the existing and the improved mathematical models are used to model Pohutu and are able to reproduce not only the interval between eruptions but also the durations of the cavern filling and the duration of the pre-play stage observed by the author on the 20th of August 1993. Fully transient numerical models, which include the eruption process itself, are developed using MULKOM and the AUTOUGH2 simulators and produce reasonably good agreement with the analytical solutions and experimental data. The model provides information about the processes inside the geyser system and models the surface discharge which cannot be modelled using the Steinberg type of model. A fully transient model for Pohutu, which is developed using the AUTOUGH2 simulator, is able to reproduce the behaviour observed by the author on the 20th of August 1993. The results of sensitivity studies show that of the three Rotorua geysers, the Feathers is the most sensitive to changes in the rate of the hot upflow from depths. Both the Feathers and Waikorohihi are more sensitive to temperature changes than Pohutu. Pohutu is currently a vigorous geyser with preliminary pulsating spring behaviour; large changes in the rate and temperature of the hot upflow would be required to stop it erupting. All geysers are sensitive to variations in the water level and temperature in Te Horu.

A phosphorus rich wastewater, typical of a dairy processing site producing milk powder, was biologically treated in a continuous activated sludge reactor. A literature review indicated there was a vast amount of information on the mechanisms of the Enhanced Biological Phosphorus Removal (EBPR) process and its application to domestic wastewaters, but little successful research on its application to dairy processing wastewater. The biodegradability of the wastewater organic fractions was assessed due to their impact on the EBPR process. Continuous anaerobic fermentation tests were used to determine the concentration of volatile fatty acids that could be generated, as these are required for successful EBPR. A fermenter hydraulic retention time of 12 hours and a temperature of 35 °C generated the highest concentration of volatile fatty acids, with an acidification rate of 65% (based on 0.45µm filtered COD). To permit improved dissolved oxygen control and increased flexibility, a multi-zone reactor was designed. A fermentation stage was also incorporated prior to the activated sludge reactor. This reactor was operated with anaerobic, anoxic and aerobic zones at an SRT of 10 days and stable biological phosphorus removal was achieved. A maximum of 41.5 mg P/L was removed and phosphorus release and PHA storage occurred in both the anaerobic and anoxic zones. The soluble COD consumed in the unaerated zones (anaerobic + anoxic) totalled 484 mg COD/L on the day of the zone study (day 158). The aerobic sludge phosphorus concentration averaged 7.0% mg P/mg VSS after system optimisation. The anaerobic volume was doubled in order to increase the anaerobic consumption of volatile fatty acids. This change increased the amount of soluble COD consumption in the unaerated zones to 632 mg P/L after 40 days but did not result in a significant increase in biological phosphorus removal. In the next series of trials, the concentration of nitrogen in the wastewater was decreased and the anoxic zone removed. This change did not improve the amount of biological phosphorus removal, which was 35 mg P/L at an SRT of 10 days. The effect of different sludge retention times was then investigated. Increasing the SRT to 15 days resulted in little change in phosphorus removal (34.5 mg P/L). Decreasing the SRT to 5 days resulted in the loss of EBPR. The medium term effect on the EBPR process by removing the fermentation stage was also assessed using an AO configuration at an SRT of 10 days. The amount of phosphorus removed decreased slightly after 34 days to 34 mg P/L, but the soluble COD consumed in the anaerobic zone increased to 624 mg P/L. It was concluded that a stable EBPR process could be established when treating a dairy processing wastewater with a continuous activated sludge reactor. The biological stability was sensitive to changes in the solids retention time and the removal of the fermentation stage.

The aim of this research was to investigate the feasibility of co-digestion of municipal primary sludge and whey by anaerobic CSTR (Continuous Stirred Tank Reactor), as well as the factors that affect the performance of the co-digestion reactors. Before studying the co-digestion process, a semi-continuous whey digestion experiment was conducted to analyze the feasibility of anaerobic digestion of whey along with pH control. The results obtained from the study indicated that supplement of nutrients, trace elements as well as heavy metals was necessary to maintain the anaerobic whey digestion system. To investigate the co-digestion of primary sludge and whey process, the effects of pH, OLR (Organic Loading Rate), HRT (Hydraulic retention time) as well as the COD (Chemical Oxygen Demand) loading ratio of primary sludge to whey on the performance of the reactors were studied. The results of the co-digestion experiments demonstrated that it was feasible to co-digest primary sludge and whey without nutrient, trace element and heavy metal supplement. The TCOD (Total Chemical Oxygen Demand) removal efficiency and the biogas production of the co-digestion system increased with the increase of OLR. At same OLR, digestion of the mixture of primary sludge and whey with higher whey content achieved higher biogas production and TCOD removal efficiency. The anaerobic co-digestion of primary sludge and whey process performed successfully at OLR of 5.8 ± 0.1g COD/l.d without pH control when the COD loading ratio of primary sludge to whey was approximately 70:30, due to the fact that the primary sludge may serve as buffering reagent. By adding sodium bicarbonate (NaHCO3) to maintain the pH at 6.9 ± 0.1, the OLR of the co-digestion reactor could reach 8.1 ± 0.1 g COD/l.d at HRT of 20 days. Moreover, by co-digestion of primary sludge and whey solution, the reactor could be operated successfully at HRT of 10 days and at OLR of 7.6 ± 0.1 g COD/l.d with COD loading ratio of primary sludge to whey of 53 : 47. The biogas production (3.2 ± 0.1 l/d) was 1.5 l/d higher than digestion of the same amount of primary sludge alone (1.7 ± 0.1 l/d).

The aim of this research was to investigate the feasibility of co-digestion of municipal primary sludge and whey by anaerobic CSTR (Continuous Stirred Tank Reactor), as well as the factors that affect the performance of the co-digestion reactors. Before studying the co-digestion process, a semi-continuous whey digestion experiment was conducted to analyze the feasibility of anaerobic digestion of whey along with pH control. The results obtained from the study indicated that supplement of nutrients, trace elements as well as heavy metals was necessary to maintain the anaerobic whey digestion system. To investigate the co-digestion of primary sludge and whey process, the effects of pH, OLR (Organic Loading Rate), HRT (Hydraulic retention time) as well as the COD (Chemical Oxygen Demand) loading ratio of primary sludge to whey on the performance of the reactors were studied. The results of the co-digestion experiments demonstrated that it was feasible to co-digest primary sludge and whey without nutrient, trace element and heavy metal supplement. The TCOD (Total Chemical Oxygen Demand) removal efficiency and the biogas production of the co-digestion system increased with the increase of OLR. At same OLR, digestion of the mixture of primary sludge and whey with higher whey content achieved higher biogas production and TCOD removal efficiency. The anaerobic co-digestion of primary sludge and whey process performed successfully at OLR of 5.8 ± 0.1g COD/l.d without pH control when the COD loading ratio of primary sludge to whey was approximately 70:30, due to the fact that the primary sludge may serve as buffering reagent. By adding sodium bicarbonate (NaHCO3) to maintain the pH at 6.9 ± 0.1, the OLR of the co-digestion reactor could reach 8.1 ± 0.1 g COD/l.d at HRT of 20 days. Moreover, by co-digestion of primary sludge and whey solution, the reactor could be operated successfully at HRT of 10 days and at OLR of 7.6 ± 0.1 g COD/l.d with COD loading ratio of primary sludge to whey of 53 : 47. The biogas production (3.2 ± 0.1 l/d) was 1.5 l/d higher than digestion of the same amount of primary sludge alone (1.7 ± 0.1 l/d).

Geysers that discharge water and steam intermittently to the atmosphere are one of the rarest natural phenomena associated with geothermal systems. Several approaches including laboratory experiments, field observations and mathematical and numerical modelling studies are used in the present study to explain the behaviour of geysers and the important parameters controlling the eruption of geysers. A particular study is made of three geysers at Rotorua geothermal field: Pohutu, Prince of Wales Feathers and Waikorohihi. The existing mathematical model (steinberg et al., 1981a) is studied and an improved mathematical model is developed to accommodate two-phase flow and the variation in fluid properties with temperature. Both the existing and the improved mathematical models are used to model Pohutu and are able to reproduce not only the interval between eruptions but also the durations of the cavern filling and the duration of the pre-play stage observed by the author on the 20th of August 1993. Fully transient numerical models, which include the eruption process itself, are developed using MULKOM and the AUTOUGH2 simulators and produce reasonably good agreement with the analytical solutions and experimental data. The model provides information about the processes inside the geyser system and models the surface discharge which cannot be modelled using the Steinberg type of model. A fully transient model for Pohutu, which is developed using the AUTOUGH2 simulator, is able to reproduce the behaviour observed by the author on the 20th of August 1993. The results of sensitivity studies show that of the three Rotorua geysers, the Feathers is the most sensitive to changes in the rate of the hot upflow from depths. Both the Feathers and Waikorohihi are more sensitive to temperature changes than Pohutu. Pohutu is currently a vigorous geyser with preliminary pulsating spring behaviour; large changes in the rate and temperature of the hot upflow would be required to stop it erupting. All geysers are sensitive to variations in the water level and temperature in Te Horu.

Anaerobic ponds are an established technology for treating farm dairy effluent in New Zealand. These ponds produce a significant amount of methane but because of their large size, they are rarely covered for methane capture. The removal of solids prior to entering the ponds would allow for shorter retention times resulting in smaller ponds that could be covered. However, removal of solids entails loss of organic material and thus methane production. It was proposed that improved hydrolysis of solid content prior to solids separation could increase the organic content of the liquid fraction. No literature was found describing two-stage (acidogenic/hydrolytic and methanogenic) systems which achieve hydrolysis combined with solids separation of manure slurries. Hence, the aim of the present study is to examine the feasibility of such a system. Five parameters were examined to determine favourable conditions for hydrolysis of solids and acidogenesis in farm dairy effluent. These were: 1) mixing, 2) hydraulic retention time (HRT), 3) liquid to solid ratio (dilution), 4) addition of rumen contents, and 5) reactor configuration. Continuous mixing of cow manure sludge inhibited net volatile fatty acid (VFA) production, likely due to oxygenation. By comparison, a once-daily brief stirring regime resulted in production of 785 mgVFA/Lsludge compared with 185 mg/L from a continuously stirred reactor. Mixing had little effect on soluble COD yield. HRTs ranging between 1 and 10 days resulted in greater hydrolysis yields (0.25 to 0.33 gCOD/gVSadded) compared with 0.15 gCOD/gVSadded for a 15-day HRT. It was hypothesised that the attachment of hydrolytic bacteria to solids prevented washout at shorter HRTs. In contrast, longer HRTs favoured VFA production. This may have been due to the planktonic nature of acidogenic bacteria, making them more vulnerable to washout at shorter HRTs. The effects of solid:liquid ratio on hydrolysis and acidogenesis were examined with sludge:water ratios ranging from 1:1 to 1:0.25. The addition of larger volumes of water resulted in improved acidogenesis with the 1:1 sludge:water mixture producing a liquor with 245% more VFA mass (635 mg) than reactors with a 1:0.25 sludge:water mixture (184 mg). Addition of rumen contents was shown to have little or no effect on either acidogenesis or hydrolysis. This may have been due to a masking effect of an increased organic load through the addition of undigested grass in the rumen. A mix, settle and decant (MSD) system and an unmixed flow-through leachbed separator system were trialled and compared as hydrolytic/acidogenic reactors. The MSD system produced 0.033gVFA/gTSadded and 0.315gCOD/gTSadded compared with 0.015gVFA/gTSadded and 0.155gCOD/gTSadded in the unmixed leachbed separator. It was hypothesised that improved mixing and longer solid-liquid contact times in the MSD system provided greater surface contact and transfer of organics to the liquid phase thereby enhancing hydrolysis. A two-stage (acidogenic/hydrolytic and methanogenic) system was tested at bench scale. A partially mixed leachbed separator was fed with manure slurry. This retained solids while leaching out a treated feed high in organic content to be fed into a variety of methanogenic systems. The leachbed separator produced a treated feed with a VFA concentration of 562 mg/L, 120% higher than the influent slurry (255 mg/L). Soluble COD increased 60% from 1,085 mg/L in the slurry to 1,740 mg/L in the treated feed. 20-day HRT and 10-day HRT unmixed unheated methanogenic reactors, both fed with treated feed from the leachbed separator, had lower specific methane yields (0.14 and 0.11 LCH4/gVS respectively) than a 50-day HRT reactor fed with untreated slurry (0.17 LCH4/gVS). However, both the 20-day HRT reactor and the 10-day reactor had higher volumetric methane yields (0.033 and 0.057 LCH4/Lreactor/day respectively) than the 50-day HRT reactor fed with slurry (0.024 LCH4/Lreactor/day). Gas production was shown to rise as the VFA levels in the treated feed rose. Fermentation in the leachbed followed by separation was shown to improve average gas production by up to 57% compared to separation alone. Field-scale trials of a leachbed separator system followed by a 20-day HRT methanogenic reactor were undertaken. VFA concentrations increased from 100 mg/l in the influent to 1,260 mg/l in the treated feed, while the soluble COD increased from 2,766 mg/L to 5,542 mg/L. The methanogenic reactor produced 0.08 m3 CH4/ m3reactor/day, four times higher than that which would be expected from a covered pond of the same size. This was hypothesised to be due to the increased biodigestability of the feed to the tank digester as well the increased organic loading rate. This study indicates that the use of a leachbed separator would be an effective low-tech strategy for reducing the HRT of farm anaerobic ponds, and reducing the size of covers required for biogas energy recovery.

Geysers that discharge water and steam intermittently to the atmosphere are one of the rarest natural phenomena associated with geothermal systems. Several approaches including laboratory experiments, field observations and mathematical and numerical modelling studies are used in the present study to explain the behaviour of geysers and the important parameters controlling the eruption of geysers. A particular study is made of three geysers at Rotorua geothermal field: Pohutu, Prince of Wales Feathers and Waikorohihi. The existing mathematical model (steinberg et al., 1981a) is studied and an improved mathematical model is developed to accommodate two-phase flow and the variation in fluid properties with temperature. Both the existing and the improved mathematical models are used to model Pohutu and are able to reproduce not only the interval between eruptions but also the durations of the cavern filling and the duration of the pre-play stage observed by the author on the 20th of August 1993. Fully transient numerical models, which include the eruption process itself, are developed using MULKOM and the AUTOUGH2 simulators and produce reasonably good agreement with the analytical solutions and experimental data. The model provides information about the processes inside the geyser system and models the surface discharge which cannot be modelled using the Steinberg type of model. A fully transient model for Pohutu, which is developed using the AUTOUGH2 simulator, is able to reproduce the behaviour observed by the author on the 20th of August 1993. The results of sensitivity studies show that of the three Rotorua geysers, the Feathers is the most sensitive to changes in the rate of the hot upflow from depths. Both the Feathers and Waikorohihi are more sensitive to temperature changes than Pohutu. Pohutu is currently a vigorous geyser with preliminary pulsating spring behaviour; large changes in the rate and temperature of the hot upflow would be required to stop it erupting. All geysers are sensitive to variations in the water level and temperature in Te Horu.