Silica scale formation and effect of sodium and aluminium ions -29Si NMR study

Silica scale formation on reverse osmosis (RO) membrane surface is a significant problem for operation of high recovery RO desalination plant. In this study we report the effects of sodium ions derived from sodium chloride and aluminium ions derived from aluminium chloride on dissolved silica species obtained from commercial sodium silicate solutions. Five dissolved silica species have been positively identified in sodium silica solutions. 29 Si NMR spectroscopy has proven to be particular well suited to obtain in situ information on the connectivity of silicon atoms in the solution and the impact of sodium and aluminium ions on connectivity between monomeric silica acid groups. Such information extends the understanding of how polysilicate ion mixtures change under different chemical conditions. Implications for RO desalination and silica scale formation on the membrane surface were discussed

Fouling of dairy components on hydrophobic polytetrafluoroethylene (PTFE) membranes for membrane distillation

This study investigates fouling of membranes during membrane distillation (MD) of two model dairy feeds — skim milk and whey, as well as their major single components. Every MD experiment was conducted for 20 hat 54 C feed inlet temperature and 5 C permeate inlet temperature using PTFE membranes. Performance was assessed in terms of throughput (flux) and retention efficiency.Skim milk flux was found to be lower but stable overtime compared to whey.The study using single components as well as combinations the reofrevealed that fouling was primarily driven by proteins and calcium, but only in combination.Lactose also played a role to a lesser extent in the protein/membrane interactions, possibly due to preferential hydration,but did not interact with the membrane polymer directly. However lactose was found to deposit once an anchorpoint to the membrane was established by other components. Skim milk showed strong adhesion from its principle proteins, caseins;however salts were needed to form a thick and dense cake layer.Caseins seem to form a layer on the membrane surface that prevents other components from interacting with the membrane polymer.Wheyproteins, on the other hand, deposited to alesse rextent. In general membrane distillation was found to be a process that generates high quality water with retention of all tested components >99% while simultaneously concentrating whey or skim milk

Stormwater harvesting potential for local reuse in an urban growth area: a case study of Melton growth area in the west of Melbourne

Integrated urban water management approaches (IUWM) are implemented to address challenges from increases in water demand as a result of population growth and the impact of climate change. IUWM aims to utilize all water resources (stormwater, wastewater, and rainwater) based on fit-for-purpose concepts. Here, a local water utility in Melbourne’s Melton growth area explored the availability of stormwater as an alternative water resource for water service planning for a proposed residential development in an existing greenfield area of 13,890 hectares for 160,000 new houses by 2040. A methodology was developed for assessing the stormwater quantity and quality under land use change and different climatic conditions considering the availability of stormwater from the proposed urban development. The modelling results indicated that the amount of annual stormwater generated in the region increased by nearly four times to 32 GL/year under the 2040 full urban land use with high climate change. The provision of constructed wetlands in proposed development blocks was found to be efficient at removing TSS, TP, and TN, and able to retain over 90% of TSS, 77% of TP, and 52% of TN in all scenarios. Harvested stormwater, if treated to potable standards, can meet nearly 40% of water requirements for residential area needs

Performance assessment of membrane distillation for skim milk and whey processing

AbstractMembrane distillation is an emerging membrane process based on evaporation of a volatile solvent. One of its often stated advantages is the low flux sensitivity toward concentration of the processed fluid, in contrast to reverse osmosis. In the present paper, we looked at 2 high-solids applications of the dairy industry: skim milk and whey. Performance was assessed under various hydrodynamic conditions to investigate the feasibility of fouling mitigation by changing the operating parameters and to compare performance to widespread membrane filtration processes. Whereas filtration processes are hydraulic pressure driven, membrane distillation uses vapor pressure from heat to drive separation and, therefore, operating parameters have a different bearing on the process. Experimental and calculated results identified factors influencing heat and mass transfer under various operating conditions using polytetrafluoroethylene flat-sheet membranes. Linear velocity was found to influence performance during skim milk processing but not during whey processing. Lower feed and higher permeate temperature was found to reduce fouling in the processing of both dairy solutions. Concentration of skim milk and whey by membrane distillation has potential, as it showed high rejection (>99%) of all dairy components and can operate using low electrical energy and pressures (<10kPa). At higher cross-flow velocities (around 0.141m/s), fluxes were comparable to those found with reverse osmosis, achieving a sustainable flux of approximately 12kg/h·m2 for skim milk of 20% dry matter concentration and approximately 20kg/h·m2 after 18h of operation with whey at 20% dry matter concentration

Effectiveness and energy requirements of pasteurisation for the treatment of unfiltered secondary effluent from a municipalwastewater treatment plant

Pasteurisation was investigated as a process to achieve high microbial quality standards in the recycling of water from unfiltered secondary effluents from a wastewater treatment plants in Melbourne, Australia. The relative heat sensitivity of key bacterial, viral, protozoan and helminth wastewater organisms (Escherichia coli, Enterococcus, FRNA bacteriophage, adenovirus, coxsackievirus, Cryptosporidium, and Ascaris) were determined by laboratory scale tests. The FRNA phage were found to be the most heat resistant, followed by enterococci and E. coli. Pilot scale challenge testing of a 2 ML/day pasteurisation pilot plant using unfiltered municipal wastewater and male specific coliphage (MS2) phage showed that temperatures between 69 &deg;C and 75 &deg;C achieved log reductions values between 0.9 &plusmn; 0.1 and 5.0 &plusmn; 0.5 respectively in the contact chamber. Fouling of the heat exchangers during operation using unfiltered secondary treated effluent was found to increase the energy consumption of the plant from 2.2 kWh/kL to 5.1 kWh/kL. The economic feasibility of pasteurisation for the current municipal application with high heat exchanger fouling potential can be expected to depend largely on the available waste heat from co-generation and on the efforts required to control fouling of the heat exchangers