Alan J. Guwy

Defining the biomethane potential (BMP) of solid organic wastes and energy crops: a proposed protocol for batch assays

The application of anaerobic digestion technology is growing worldwide because of its economic and environmental benefits. As a consequence, a number of studies and research activities dealing with the determination of the biogas potential of solid organic substrates have been carrying out in the recent years. Therefore, it is of particular importance to define a protocol for the determination of the ultimate methane potential for a given solid substrates. In fact, this parameter determines, to a certain extent, both design and economic details of a biogas plant. Furthermore, the definition of common units to be used in anaerobic assays is increasingly requested from the scientific and engineering community. This paper presents some guidelines for biomethane potential assays prepared by the Task Group for the Anaerobic Biodegradation, Activity and Inhibition Assays of the Anaerobic Digestion Specialist Group of the International Water Association. This is the first step for the definition of a standard protocol.

The occurrence of pharmaceuticals, personal care products, endocrine disruptors and illicit drugs in surface water in South Wales, UK

The presence and fate of 56 pharmaceuticals, personal care products, endocrine disruptors and illicit drugs (PPCPs) were investigated in the South Wales region of the UK. Two contrasting rivers: River Taff and River Ely were chosen for this investigation and were monitored for a period of 10 months. The impact of the factors affecting the levels of concentration of PPCPs and illicit drugs in surface water such as surrounding area, proximity to wastewater effluent and weather conditions, mainly rainfall was also investigated. Most PPCPs were frequently found in river water at concentrations reaching single microgL(-1) and their levels depended mainly on the extent of water dilution resulting from rainfall. Discharge of treated wastewater effluent into the river course was found to be the main cause of water contamination with PPCPs. The most frequently detected PPCPs represent the group of pharmaceuticals dispensed at the highest levels in the Welsh community. These were antibacterial drugs (trimethoprim, erythromycin-H(2)O and amoxicillin), anti-inflammatories/analgesics (paracetamol, tramadol, codeine, naproxen, ibuprofen and diclofenac) and antiepileptic drugs (carbamazepine and gabapentin). Only four PPCPs out of 56 (simvastatin, pravastatin, digoxin and digoxigenin) were not quantified over the course of the study. Several PPCPs were found to be both ubiquitous and persistent in the aqueous environment (e.g. erythromycin-H(2)O, codeine, carbamazepine, gabapentin and valsartan). The calculated average daily loads of PPCPs indicated that in total almost 6 kg of studied PPCPs are discharged daily into the studied rivers. The illicit drugs studied were found in rivers at low levels of ng L(-1). Average daily loads of amphetamine, cocaine and its main metabolite benzoylecgonine were as follows: 8, 1.2 and 39 gday(-1), respectively. Their frequent occurrence in surface water is primarily associated with their high illegal usage and is strongly associated with the discharge of insufficiently treated wastewater effluent.

The effect of signal suppression and mobile phase composition on the simultaneous analysis of multiple classes of acidic/neutral pharmaceuticals and personal care products in surface water by solid-phase extraction and ultra performance liquid chromatography–negative electrospray tandem mass spectrometry

A new multi-residue method for the determination of 25 acidic/neutral pharmaceuticals (antibiotics, anti-inflammatory/analgesics, lipid regulating agents, diuretics, triazides, H2-receptor antagonists, cardiac glicozides and angiotensin II antagonists) and personal care products (sunscreen agents and preservatives) in surface water with the usage of a new technique: ultra performance liquid chromatography-negative electrospray tandem mass spectrometry (UPLC-MS/MS) was developed and validated. The novel UPLC system with 1.7 microm particle-packed column allowed for good resolution of analytes with the application of low mobile phase flow rates (0.05 mL min(-1)) and short retention times (from 4.7 min to 13.3 min) delivering a fast and cost-effective multi-residue method. SPE with the usage of Oasis MCX strong cation-exchange mixed-mode polymeric sorbent was chosen for sample clean-up and concentration. The influence of mobile-phase composition, matrix assisted ion suppression and SPE recovery on the sensitivity of the method was identified and quantified. The instrumental limits of quantification varied from 0.2 microgL(-1) to 30mugL(-1). The method limits of quantification were at low nanogram per litre levels and ranged from 0.3 ng L(-1) to 30 ng L(-1). The instrumental and method intra-day and inter-day repeatabilities were on average less than 5%. The method was successfully applied for the determination of PPCPs in River Taff. Thirteen compounds were determined in river water at levels ranging from a single to a few hundred nanograms per litre. Among them were ten pharmaceuticals (aspirin, salicylic acid, ketoprofen, naproxen, diclofenac, ibuprofen, mefenamic acid, furosemide, sulfasalazine and valsartan) and three personal care products (methyl- and ethylparaben and 4-benzophenone).

The effect of acid pretreatment on the anaerobic digestion and dewatering of waste activated sludge

Waste activated sludge (WAS) is difficult to degrade in anaerobic digestion systems and pretreatments have been shown to speed up the hydrolysis stage. Here the effects of acid pretreatment (pH 6-1) using HCl on subsequent digestion and dewatering of WAS have been investigated. Optimisation of acid dosing was performed considering digestibility benefits and level of acid required. Pretreatment to pH 2 was concluded to be the most effective. In batch digestion this yielded the same biogas after 13 days as compared to untreated WAS at 21 days digestion. In semi-continuous digestion experiments (12 day hydraulic retention time at 35°C) it resulted in a 14.3% increase in methane yield compared to untreated WAS, also Salmonella was eradicated in the digestate. Dewatering investigations suggested that the acid pretreated WAS required 40% less cationic polymer addition to achieve the same cake solid content. A cost analysis was also carried out.

Illicit drugs and pharmaceuticals in the environment – Forensic applications of environmental data. Part 1: Estimation of the usage of drugs in local communities

Pharmaceuticals and recently also illicit drugs have been recognised as emerging environmental contaminants due to their potential environmental impact: frequent occurrence, persistence and risk to aquatic life and humans. This manuscript is part one of the two-part study aiming to provide a better understanding and application of environmental data not only for environmental aims but also to meet forensic objectives. An attempt to use wastewater data is made in order to verify patterns of the usage of drugs (in particular illicit) in local communities. The average usage of cocaine in South Wales was estimated at 0.9 g day(-1) 1000 people(-1), which equals 1 tonne of this drug used or disposed of to sewage annually in Wales. The calculated usage of amphetamine denoted 2.5 g day(-1) 1000 people(-1) and is suspected to be an overestimate. Because no analysis of enantiomers of amphetamine was undertaken, no distinction between amphetamines legal and illicit usage could be made.

Modular tubular microbial fuel cells for energy recovery during sucrose wastewater treatment at low organic loading rate.

Energy recovery while treating low organic loads has been investigated using longitudinal tubular microbial fuel cell (MFC) reactors. Duplicate reactors, each consisting of two modules, were operated with influent sucrose organic loading rates (OLRs) between 0.04 and 0.42 g COD/l/d. Most soluble COD (sCOD) removal occurred in the first modules with predominantly VFAs reaching the second modules. Coulombic efficiency (CE) in the second modules ranged from 9% to 92% which was 3-4 times higher than the first modules. The maximum energy production was 1.75 W h/g COD in the second modules at OLR 0.24 g/l/d, up to 10 times higher than the first modules, attributable to non-fermentable substrate. A simple plug flow model of the reactors, including a generic non-electrogenic reaction competing for acetate, was developed. This modular tubular design can reproducibly distribute bioprocesses between successive modules and could be scalable, acting as a polishing stage while reducing energy requirements in wastewater treatment.

Life cycle assessment of biogas infrastructure options on a regional scale

A life cycle assessment has been completed of potential biogas infrastructures on a regional scale. Centralised and distributed infrastructures were considered along with biogas end uses of Combined Heat and Power (CHP) and injection to the gas grid for either transport fuel or domestic heating end uses. Damage orientated (endpoint) life cycle impact assessment method identified that CHP with 80% heat utilisation had the least environmental impact, followed by transport fuel use. Utilisation for domestic heating purposes via the gas grid was found to perform less well. A 32% difference in transportation requirement between the centralised and distributed infrastructures was found to have a relatively small effect on the overall environmental impact. Global warming impacts were significantly affected by changes in methane emissions at upgrading stage, highlighting the importance of minimising operational losses.

Fermentative biohydrogen production systems integration

Acidogenic fermentation can be used to produce hydrogen from a range of biomass sources. The effluent from this process can be utilised in a number of biological processes enabling further recovery of energy from the biomass. In this review a number of candidate technologies are assessed including conventional methanogenic anaerobic digestion, dark fermentative hydrogen production, photo-fermentation, and bioelectrochemical systems. The principles, benefits and challenges associated with integrating these technologies are discussed, with particular emphasis on integration with fermentative hydrogen production, and the current state of integrative development is presented. The various system configurations for potential integrations presented here may simultaneously permit an increase in the conversion efficiency of biomass to energy, improved adaptability to varying operating conditions, and improved stability. Such integration, while increasing system complexity, may mean that these bioprocesses could be deployed in a wider range of scenarios and be used with a greater range of substrates.

Microbial fuel cell type biosensor for specific volatile fatty acids using acclimated bacterial communities.

Volatile fatty acid (VFA) concentration is one of the most important parameters for monitoring bio-processes such as anaerobic digestion and microbial fuel cells. In this study the correlation between VFA concentration and current/voltage responses and electrochemical properties by using the MFC technology was evaluated. The discrimination between different species of VFA by using two methods i.e., coulombic efficiency and cyclic voltammetry was investigated. Columbic efficiency gave a slow response of greater than 20h, particularly at concentration levels of 20mgl(-1). By using cyclic voltammetry to measure the oxidation peak at a consistent scan rate showed linear correlation to VFA concentration and peak current produced, up to <40mgl(-1)) in a rapid response time of 1-2min. The results presented showed good correlations between the individual VFA species concentration and charge, and also current generated. A MFC based biosensor array was produced capable of measuring individual acetate, propionate and butyrate concentrations with sensitivity down to 5mgl(-1) and up to 40mgl(-1).

Hydrogen production from sewage sludge using mixed microflora inoculum: effect of pH and enzymatic pretreatment.

Hydrogen was successfully produced by fermenting primary sewage sludge which had been both heat treated and digested with a commercially available enzyme preparation. When either heat treatment or enzymatic digestion were not used, no hydrogen was produced during fermentation. Heat treated mesophilic anaerobic sludge was used as an inoculum rather than a pure microbial culture. Fermentation was conducted at pH levels ranging from of 4.5 to 7.0. When fermentation took place at pH 5.5 a peak hydrogen production rate of 3.75 ml min(-1) was observed. At this pH the hydrogen yield was 0.37 mol H(2)mol(-1) carbohydrate, equivalent to 18.14L H(2)kg(-1) dry solids.