Phosphorus (P) pollution of waterbodies is a global issue with detrimental environmental, social and economic impacts. Low-cost and sustainable P removal technologies are therefore required to tackle P pollution, whilst also offering a technique for reclaiming P. Ochre, a waste product from minewater treatment plants (MWTPs), has been proposed as a suitable material for the removal of P from enriched waters due to a high content of Fe, Al, Ca and Mg, which have high affinities for P removal. Whilst a range of studies have been conducted investigating ochre as a P adsorbent, most of these are large-scale field experiments and lack understanding of the underlying processes of P removal by ochre. There have also been very few detailed comparisons of different ochre types. The primary focus of this thesis is thus to provide a process-based understanding of P removal by various ochres, in order to investigate the optimal conditions for the use of ochres in the treatment of aquatic P pollution. Seven ochres from six MWTPs in the UK and Ireland were investigated, one of which was in a pelleted form. The ochres were largely comprised of Al, Ca, Fe and Mg (42-68 % by dry weight), had a high B.E.T. surface area, 56-243 m2 g-1, and contained mineral surfaces with a high affinity for P adsorption, such as goethite and calcite. A novel batch experiment methodology was utilised to calculate the adsorption characteristics of ochre at discrete pH conditions. The variation of these characteristics with pH indicates the importance and requirement for such a method to study adsorption by materials at the expected pH conditions of application. At the pH conditions of wastewater streams (~pH 7), the P adsorption capacities of the ochres, determined from fitting adsorption isotherms, was 11.8–43.1 mg P g-1. Results of P adsorption batch experiments were modelled in ORCHESTRA, wherein P removal by the ochres was described well by adsorption onto hydrous ferric oxides. Three of the ochres contain relatively high calcite contents and due to a poor fit of the model to the observed datasets at high pH conditions, with equilibrium P concentrations lower in the batch experiments than the modelled result, adsorption onto calcite is suggested as a P removal mechanism for these ochres at pH > 7. Environmental application of ochre filters will require P removal under flow-through transport conditions. Column experiments were therefore conducted using two ochres, coarse-grained Polkemmet ochre and Acomb pellets (column volume 1055 cm3, pore space 490-661 cm3, typical pore volumes of experiments: 220-400). P removal efficiency increased with contact time, and the presence of competing ions had only marginal effects on P removal. Resting the column substrate for 48 hours between P applications greatly increased the P removal efficiency of a packed column of Polkemmet ochre, resulting in 81 % of influent P removed over 1000 pore volumes of operation (7.68 mg P g-1). Acomb pellets had a lower P removal efficiency than Polkemmet ochre. It is suggested that the high calcium content of the pellets, as a result of the pelletisation process, has created a substrate where the dominant P removal mechanism at neutral pH conditions is adsorption to calcite, which has slower reaction kinetics than adsorption onto goethite. Therefore, this pelleted ochre requires a higher contact time for adsorption reactions to occur. It is suggested that ochre filters are most suitable for application in situations where flow rate is constant or can be controlled e.g. septic tank effluent. Ochres which dry to a coarse particle size are preferred for use as a substrate as pelletisation requires capital, expertise and can produce substrates with slower P sorption kinetics. Resting the filter substrate between P application regenerates surface sites for adsorption, and filters should be run in parallel to maximise P removal efficiency. Acomb pellets, which are a mix of iron hydroxides and alkaline materials, may have potential application as a permeable reactive barrier substrate to treat P enriched ground waters. Further research utilising fine-grained ochres as an additive to P rich fertilisers or for use in continuously stirred tank reactors is recommended.

Nutrients (nitrogen and phosphorus) should be removed and recycled from wastewater in order to reduce the nutrient load to recipient waters, avoiding contamination of groundwater and conserve resources. There is a need to pay more attention to phosphorus (P) removal and recycling from wastewater due to limited availability of phosphorus recourses. For such purpose reactive filter media can be used to remove nutrient from wastewater as a sustainable technology. The present study was aimed to evaluate calcium silicate hydrate crystallization in Absol as a reactive filter media for removal and recycle of phosphorus from household wastewater and assess physical and chemical characteristics of Absol. A study of the color removing capacity of Absol was also performed. Several batch experiments were done for comparing absorption mechanism. Collected data were applied to Langmuir and Freundlich isotherm models to study type of adsorption isotherms and pseudofirst- order and second order models were run for study of adsorption kinetics. The experiment demonstrated a very high P and Methylene Blue (MB) sorption capacity. The amount of adsorbed P and MB vary with initial solution concentrations, contact time, and adsorbent dosage. Both equilibrium data (P, MB) were fitted very well in the Langmuir isotherm equation, confirming the monolayer physical sorption and adsorption kinetic followed by the pseudo-second order kinetic model. It is concluded that Absol can have potential to be use for the removal of P, textile dye contaminants and probably also pharmaceuticals present in wastewater.

Orange cultivation is a huge industry which increasing for each year. By the year 2010 theorange production of the world is expected to reach 66.4 million tons per year. Most of theoranges are used for orange juice production. Consequently, a large amount of organic wastes,including seeds, segment membranes and peel, counting up to half of the weight of usedoranges, are generated As alternatives to land filling and incineration, source separation andcomposting together with biogas production are being considered as suitable methods fortreating this fraction of wastes, because it holds a high amount of organic materials in form ofvaluable carbohydrate polymers. However, the presence of peel oil, limonene, known to haveantimicrobial effects, has showed to be a strong inhibitor for the biogas producingmicroorganisms. Therefore the orange peel waste (OP) was mixed with the organic fraction ofmunicipal solid waste (MSW) in this study to keep the concentration of this inhibitorycompound at low level.Based on the results from previous batch experiments, this study was performed in order toconfirm and develop the possible use of orange peel waste in biogas production. Since thebatch experiments showed that the methane production was not affected, when a mixture of70% MSW and 30% OP (calculated on the basis of volatile solids (VS) content added) wasused as substrate, a continuous anaerobic digestion experiment was performed using the samemixture of MSW and OP as a substrate in this study. Furthermore, a reactor utilizing onlyMSW was used as a control. Both reactors were operated during 35 days at thermophilicconditions (55ºC), with an organic loading rate of 3gVS/L/day and a hydraulic retention timeof 21 days. The methane production was around 0,5 Nm3/kgVS/day in both reactors duringthe first period of operation. However, the production of methane started to decrease after 20days followed by a sharp decrease during the last 5 days in the orange peel-containing reactor.Furthermore, a steadily increase (from 4,85g/L to 6,51g/L) in the total content of volatile fattyacids (VFA) could be observed here, while the total content of VFA in the control reactorremained at low levels (0,84g/L). A second experimental set up using a decreased amount ofOP (20% OP and 80% MSW) in the substrate mixture and operating at the same conditions sthe previous experiment was also performed and showed similar trends in the results. Thefailure of the process can be explained by inhibition in the system, which led to theaccumulation of VFA’s resulting in a decreased and finally no methane production. Thisinhibition might be caused by the accumulation of the inhibitory compound, limonene,presented in the orange peel waste. Therefore some treatment of the OP is necessary prior todigestion to avoid this inhibition. Batch digestion of treated vs untreated OP showed that themethane production of treated OP could be increased to 0,628 Nm3/kgVS compared to that of0,408 Nm3/kgVS from the untreated sample. Further investigations utilizing this treated OPfraction in continuous biogas process are necessary in the future.

Eutrophication due to excess loading of phosphorus (P) is a leading cause of water quality degradation within the United States. The aim of this study was to investigate P removal and recovery with 12 materials (four calcite varieties, wollastonite, dolomite, hydroxylapatite, eggshells, coral sands, biochar, and activated carbon. This was accomplished through a series of batch experiments with synthetic wastewater solutions ranging from 10-100 mg PO₄-P/ L. The results of this study were used to establish large-scale, calcite-based column filter experiments located in the Rubenstein School of Environment and Natural Resources' Eco-Machine. Influent and effluent wastewater samples were routinely collected for 64 days. Measures of filter performance included changes in pH, percent reduction and mass adsorbed of P. After the columns reached saturation, filter media was analyzed for the mineralogical content by X-ray powder diffraction (XRD). In the batch experiments, P removal and recovery varied among the media and across treatments. The best performing minerals were calcite, wollastonite, and hydroxylapatite. Eggshells, activated carbon, and coral sands also reduced and adsorbed P. The remaining materials had the lowest reductions and adsorption of P. Results from batch experiments informed the design of large column filters within the Rubenstein School of the Environment and Natural Resources' Eco-Machine. Removal and adsorption rates of P by the three column filters were similar. The columns achieved an average P reduction of 12.53% (se = 0.98) and an average P adsorption of 0.649 mg PO₄-P/ kg media (se = 0.03) over a 4-h hydraulic retention time. Paired T-tests showed that P reductions were statistically significant (p-value < 0.05) on the majority of sampling dates until the columns reached saturation. Saturation was reached after 31 days for two of the columns and 36 days for the third column. The filter media consistently buffered the pH of the wastewater to approximately 6.0-7.0 with no indication of diminishing buffer capacity after saturation. XRD analysis was not able to detect any P species within the crystalline structure of the filter media. This research contributes to the understanding of how the selected media perform during P removal and recovery programs, while providing information on the performance of large column filters operating within advanced, ecologically engineered wastewater treatment systems.

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