Effect of Aluminium Salt Dosing on Activated Sludge Settleability Indicators: A New Settleability Model Development

There has been a significant rise in the use of aluminium salts (Al3+) for the chemical precipitation of phosphates in wastewater treatment plants due to growing stricter regulatory requirements for wastewater effluent release to the environment. The modelling of the settleability of the resultant Al3+ sludge in present engineering practice for design and optimisation are still based on conventional sludge settleability models. This paper describes a novel activated sludge settleability model which is designed to analyse the effects of Al3+ dosing on activated sludge settleability indicators, zone settling velocity (ZSV), and stirred specific volume index (SSVI). The impact of Al3+ dosing concentrations on ZSV and SSVI of full scale activated sludge plant were analysed in the laboratory over a three years’ period and the exponential form of the Vesilind equation was optimised and validated to include alum chemical dosing parameters. The proposed model equation was found to effectively describe the settleability of Al3+ dosed sludge for dosing concentrations range of 0 to 100 mg/L

The Impact of Aluminium Salt Dosing for Chemical Phosphorus Removal on the Settleability of Activated Sludge

The use of metal salts like aluminium in the precipitation of phosphorus in activated sludge plants has increased considerably in recent years due to the need to achieve tighter discharge consents for phosphorus in treated wastewater effluent. The impact of aluminium salt (Al3+) dosing on the settleability of activated sludge as a function of zone settling velocity (ZSV) and stirred specific volume index (SSVI) were investigated in batch settleability tests over a three-year period. The results showed that ZSV increased with increasing dose of aluminium salt as SSVI decreased. This trend was observed for dosing concentrations of less than 100 mg/L. At a dose concentration >100 mg/L, the trend was reversed as ZSV decreased and SSVI increased. At dose concentrations of <100 mg/L, Al3+ helped in the bioaggregation of dispersed activated sludge flocs, thereby improving settleability. The surface morphology from the scanning electron microscope (SEM) images indicated that the initial potential of interfloc bridging, open floc formation, and spindly bulking noticed in the undosed activated sludge flocs were remarkably reduced as the flocs became more compacted after Al3+ treatment. At >100 mg/L of Al3+, the sludge settleability started to disintegrate due mainly to surface charge reversal linked to the formation of aluminium hydroxides and the resultant disintegration of the activated sludge floc structure

Kinetics, Isotherms, and Thermodynamic Modeling of the Adsorption of Phosphates from Model Wastewater Using Recycled Brick Waste

Phosphates in wastewater at elevated concentrations cause eutrophication of water bodies and their removal from treated wastewater is essential before effluents are discharged to the environment. Phosphates are predominately removed during wastewater treatment by chemical precipitation which is usually expensive and has a significant environmental footprint. The purpose of this study was to investigate the effectiveness of waste recycled bricks as adsorbent for phosphate removal during wastewater treatment. The kinetics, isotherms, and thermodynamics of adsorption were investigated to establish the mechanisms of adsorption. The results showed that adsorption capacities increased with an increase in contact time, adsorbent dosage, and initial phosphate concentration. The kinetic study indicated that adsorption was governed by several mechanisms with various processes dominating different stages of the adsorption. The adsorption process was better represented by the pseudo-second-order kinetics and the Langmuir isotherm adequately described the adsorption of phosphates onto brick particles with a maximum adsorption capacity of 5.35 mg/g. The thermodynamic studies showed that the adsorption process was exothermic and proceeded spontaneously, demonstrating that waste bricks can be used as a sustainable alternative for the effective removal of phosphates from wastewater

Brexit and UK Energy Security:Perspectives from Unconventional Gas Investment and the Effects of Shale Gas on UK Energy Prices

Many aspects of the present and future effects on the UK economy, industry, and households, of Brexit have been researched. One thing which appears certain about Brexit is the shadow of uncertainty it casts on the future of business in the UK and its telling effects on the UK economy. It is believed that Brexit has negatively affected the level of investments in the UK, including investments in energy and crucially the upstream oil and gas, with the UK North Sea being starved of investments since 2014, leading already to increased energy bills. The UK is a net importer of natural gas—a major source of its energy, with some dependence on supplies from interconnectors from Europe. At the same time, UK energy companies participate in the common energy market which enables them to undertake arbitrage trading under the common market rules. However, both of these benefits could be lost under a Brexit scenario where the UK and EU come to a no-deal or hard border arrangement. Meanwhile, domestic production of energy in the UK has declined for nearly two decades now and import bills for natural gas are growing—they were £14.2 billion in 2017; £11.7 billion in 2016 and £13.4 billion in 2015—with Government projections indicating an upward trajectory for natural gas imports. It is however believed that the UK has great potential to exploit shale gas to her advantage in order to reduce her reliance on foreign energy which is: (1) less predictable in terms of supply and price affordability and (2) dependent on exchange rates—a primary means through which energy prices increased in 2016/17 post-Brexit referendum vote. The current study extends discussions on shale gas to cover a review of the potential of natural gas from shale formations to cushion UK households against further erratic gas prices due to Brexit and also assesses the potential effects Brexit may have had on the level of investments in shale gas, in order to suggest policy options for government consideration. Contrary to popular studies, we find evidence to suggest that shale gas has the potential to reduce energy prices for UK businesses and households at commercial extractions, under both hard and soft Brexit scenarios, but with more benefits under hard Brexit. Importantly, we find that from 2008 to 2017, average UK net export of natural gas was 5,191 GWh per year to the EU. We also find and argue that Brexit may have starved the nascent fracking industry of investments in a similar way it did to investments in conventional oil and gas and could have increased investor risk premium for shale gas development, the ultimate effect of which was a categorisation of fracking (company stock) as riskier asset for investors on the London Stock Exchange. We recommend that shale gas development be expedited to maximise its benefits to UK energy consumers post-Brexit or economic benefits from the resource could be diminished by rising operator costs due to delays and effects of the public’s perceived negative opinion of the method of extraction