Applying a circular economy model to wastewater treatment. Pete Vale WWT Wastewater st January, Birmingham

Transcription

1 Applying a circular economy model to wastewater treatment Pete Vale WWT Wastewater st January, Birmingham

2 THE CIRCULAR ECONOMY The linear economic model where we take, make and dispose of things is not sustainable. It relies on large quantities of cheap easily accessible materials and energy. A circular economy is one that keeps resources in use for as long as possible then recovers and regenerates products and materials at the end of each service life In the Water Industry, we can play an important role in the emerging circular economy - we receive huge amounts of waste water that is full of material that can be recovered and regenerated. From CIWM Journal Online 1

3 WASTEWATER TREATMENT AND THE CIRCULAR ECONOMY There s a lot of good stuff in sewage! Material Amount per head per year Reusable water 91.3m 3 Cellulose Biopolymers Phosphorus (for incorporation in P compounds) Nitrogen (for incorporation in N compounds) 6.6kg 3.3kg 0.9kg 4.6kg Methane 12.8m 3 Organic fertiliser 9.1kg Verstraete et al. (2009) Bioresource Technology 100, Salehizadej and van Loosdrecht (2004) Biotechnology Advances 22,

4 A Horizon 2020 EU funded research programme Involving: 9 countries 25 partners (including STW) 9.3 million of research funding Aim: Scale up of low carbon footprint MAterial Recovery Techniques in existing wastewater Treatment Plants 9 Pilots to be optimised over 2 years 7 recovery processes 2 downstream material processing plants THE SMART-Plant PROJECT 3

5 SMARTech No. SMART-PLANT DEMONSTRATION TRIALS Technology / Process Location Products 1 Cellulose recovery from crude sewage Geestmerasmbacht (Netherlands) 2a Anaerobic treatment of sewage Karmiel (Israel) Biogas 2b Novel BNR configuration (SCEPPHAS) for sewage treatment Manresa (Spain) Cellulosic sludge & refined clean cellulose Phosphorus (struvite), PHA (for bio-plastics) 3 Tertiary hybrid IX for N & P recovery Cranfield (UK) Nutrients N & P fertilisers 4a 4b Novel nitritation/denitritation & EBPR sludge liquor treatment process (SCENA) with conventional AD Novel nitritation/denitritation & EBPR sludge liquor treatment process (SCENA) with THP 5 Novel BNR configuration (SCEPPHAR) for sludge liquor treatment Carbonera (Italy) Psyttalia (Greece) Carbonera (Italy) P rich sludge & VFA P rich sludge PHA, struvite, VFA 4

6 DEMONSTRATION TRIALS DOWNSTREAM PROCESSING OF RECOVERED MATERIALS SMARTech No. Downstream A Downstream B Technology / Process Location Products Formulation and extrusion of the recovered cellulose and bio-plastics into biocomposite construction products Composting of P rich sludge with zeolite, and bio-drying of cellulosic sludge to produce a biofuel. London (UK) Manresa (Spain) Sludge Plastic Composite (SPC) P rich compost & bio-fuel 5

7 CELLULOSE RECOVERY IT'S ALL ABOUT THE TOILET PAPER! Toilet paper is ~ 80% cellulose 12 to 18 kg per person per year (Brits use the most!) On average 8.5 pieces of paper per visit km per day disappears down the toilet in The Netherlands On average, a person spends 43 hours a year on the toilet 70% fold the sheets before using them, 29% create something while folding! Source: 6

8 CELLULOSE RECOVERY FROM SEWAGE Fine sieving of crude sewage (mesh <0.35mm) will remove cellulose fibres efficiently The SMART Plant project will use the Salsnes filter technology A cellulose recovery plant is being built at Geestmerasmbacht WwTW in the Netherlands This produces a cellulose rich sludge typically 70-80% cellulose (with hair, fat, sand as impurities) Fine sieving as alternative to PSTs gives other benefits: Reduction in energy used in d/stream biological process (~15-20% energy saving) Lower secondary sludge prodn & hence reduced poly consumption for dewatering. Less maintenance due to increased removal of hair, rages etc. Cellulosic sludge can be directly used as biofuel and SMART Plant project will be evaluating this in Manresa, Spain. 7

9 PRODUCTION OF REFINED CLEAN The SMART Plant will produce a refined clean cellulose product using CELLULOSE BWA s CellVation process. Cellulosic sludge is disinfected, the sand/grit removed & fibres separated and dried. The Geestmerambacht plant will produce 400kg of clean cellulose/day and be operational by mid April 2017 Cellulose can also be re-used in a number of higher value products but impurities will need to be removed. As a fibre in bio-composite materials (Brunel Uni, SMART Plant) As dewatering filter media As a carbon source e.g. for production of fatty acids, activated C, or oil (has been used in asphalt) 8

10 Polyhydroxyalkanoate (PHA) is a type of biopolymer stored inside certain bacteria (e.g phosphate accumulating organisms) as granular energy reserves. Biopolymers can be extracted to produce biodegradable thermoplastics. Biopolymer plastics share similar mechanical properties to typical petroleum based plastics: can be used for applications in the packaging, agricultural, plastic and medical industries. Demand for PHA plastics is limited due to the high production costs. Production of biopolymers using wastewater sludge can reduce PHA biopolymer costs whilst simultaneously recovering carbon from wastewater treatment and converting it to a high value product. BIO-PLASTICS FROM SEWAGE Facultative Bacteria Bio-P bacteria Anaerobic Aerobic Cell Growth Energy rbcod (fermentable substrate) O 2 CO 2 VFA s PHA PHA Energy (ATP) Poly- P Energy Poly- P PO 4 PO 4 9

11 THE PROCESS OF BIO-PLASTIC 1. Enrichment: Application of env. Conditions that favours growth of PRODUCTION PHA accumulating microbes Cyclical anaerobic/aerobic conditions Feast famine cycles (dynamic feeding of VFA under anaerobic conditions) 2. Fermentation: PHA accumulating microbes require VFA as carbon source, so in a separate fermentation step organic material in sewage needs converting to VFA 1. Accumulation: Biomass from enrichment stage transferred to separate accumulation reactor. VFA from fermentation step fed under controlled conditions to optimise PHA uptake and storage. 2. Recovery: Biomass removed & subjected to a series of processes to separate the PHA granules. Solvent extraction Chemical digestion Enzyme digestion Mechanical extraction 10

12 Effluent to ASP Fermentation Sludge to AD CARBONERA SIDESTREAM S.C.E.P.P.H.A.R. PROCESS Enrichment Accumulation Recovery 11

13 ION EXCHANGE FOR N AND P REMOVAL AND FERTILISER RECOVERY New media enables smart sorption and recovery Tertiary process - can meet very tight nutrient limits Nutrients recovered as fertilisers Calcium phosphate Ammonium sulphate Recovery can be cheaper than traditional solutions 12

14 PHOSPHATE REMOVAL MEDIA - NANO-PARTICLE EMBEDDED IX Capacity 2 g P/ kg media Regeneration 5% NaOH Schematic courtesy of 13

15 REGENERANT CLEAN UP & P RECOVERY Demonstration Plant at Packington STW 14

16 AMMONIA REMOVAL MEDIA - MESOLITE MesoLite ion exchange medium Chemical modification of clay minerals and other aluminium-bearing minerals Regeneration 5-10% NaCl acid-side θ Ammonia recovered from regenerant as ammonium sulphate. NH3 + H2SO4 (NH4)2SO4 Porous membrane brine-side NH3 15

17 We need to be transitioning to a circular economy CONCLUSIONS The Water Industry is favourably placed to play an significant and important role in delivering this. We have made significant progress over the last few years, particularly with respect to energy recovery However there remains plenty of untapped resources in sewage such as nutrients, cellulose and bio-plastics and we should move from seeing wastewater treatment plants to bio-refineries. The SMART-Plant project aims to develop technologies that can be retrofitted to existing STW s to realise this vision 16

18 o THANK YOU