WASTEWATER TREATMENT STRATEGY R2IC Trials 1
URBAN VISION 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” www.wrap.org.uk From CIWM Journal Online – • In the Water Industry, we can play an important role in the www.ciwm-journal.co.uk emerging circular economy - we receive huge amounts of “waste” water that is full of material that can be recovered and regenerated. 3
WASTEWATER TREATMENT AND THE CIRCULAR ECONOMY • There’s a lot of good stuff in sewage! Material Amount per head per year 91.3m 3 Reusable water Cellulose 6.6kg Biopolymers 3.3kg Phosphorus (for incorporation in P compounds) 0.9kg Nitrogen (for incorporation in N compounds) 4.6kg 12.8m 3 Methane Organic fertiliser 9.1kg Verstraete et al. (2009) Bioresource Technology 100, 5537 – 5545 4 Salehizadej and van Loosdrecht (2004) Biotechnology Advances 22, 261 – 279
THE W W TW OF THE FUTURE? • Can we build a sewage treatment Enhanced flowsheet that gives us a truly energy Primary Nutrient rich positive WWTP? eluent anMBR Primary Recover Screen Treatment • nutrients How can we reduce the energy tactor tactor Raw N-Con P-Con wastewater consumption of the treatment process? Primary • How can we recover and generate more sludge pump Treated effluent Disposal of gross energy from sewage treatment? solids ry / 2 ry 1 Produced biogas sludge Thickener Sludge recirculation Thickened • AnMBR loop to heat exchanger Can we recover and extract the value from Primary Gas sludge engine pump the useful material that exists in Retain Sludge Imported grid Digested sludge pump electricity AD for optimum Anaerobic digester wastewater? Sludge supernatant energy balance Stabilised sludge to land 5
RESOURCE RECOVERY & INNOVATION CENTRE #R2IC 6
RESOURCE RECOVERY AND INNOVATION CENTRE • Dedicated wastewater research and development resource • A controlled, safe and flexible plug-and-play testbed • ICA development facility • Crude and settled sewage feeds from main works • Tanker reception facility • Dedicated biogas and chemical dosing systems • Conference room • A fully equipped waste laboratory 7
CURRENT PROGRAMME FOCUS Urban wastewater strategy Carbon neutral + resource recovery Chemical Energy efficiency Resource recovery Water quality Catchment focus efficiency Other 14 Severn Trent energy use - GWhrs/a Rural Works 19 Waste 415 Other 145 Sludge Large Works 58 285 ASPs Water Pumping Biggest opportunity to Totex 512 140 53 efficiency 8
INNOVATION TRIALS • • Enhanced Primary Treatment (EHPT) – Microflotation Improving Secondary Treatment – Membrane Aerated Biofilm Reactors (MABR) • Mainstream Anaerobic Treatment – Combining UASB, U/F membranes & Degassing system 9
ENHANCED PRIMARY TREATMENT Enviplan AQUATECTOR Microflotation Developed for aquaculture and proven in industrial applications, not UK wastewater treatment. High efficiency (DAF) separation process using 30 μ m air bubbles to separate solids. Much finer than similar water treatment processes. No coalescing of bubbles. 10
ENHANCED PRIMARY TREATMENT Trials • Enhance BOD & SS removal • Improve sludge quality • Optimise recycle rates • Test under diurnal/storm conditions, consideration for peak lopping 11
IMPROVING SECONDARY TREATMENT Membrane Aerated Bio-film Reactors (MABRs) Uses hollow fibre membranes to support and aerate biofilms. Existing technology but rarely retrofitted – so little used. Side-by- side trial of two MABRs (Oxymem & Suez) in existing ASP lanes. Third ASP lane to run as control. 12
IMPROVING SECONDARY TREATMENT Trials • Ease of installation • Determine O & M requirements • Compare ‘plug & play’ of Suez with bespoke fitting of Oxymem units 13
ANAEROBIC MAINSTREAM TREATMENT • Anaerobic treatment of wastewater uses the same biological processes as sludge AD. • Anaerobic processes have been used to treat higher strength industrial wastewaters for many years. • Most applications use upflow anaerobic sludge blanket reactors (UASBs); • Flocculant, or • Granular • Applicability – small decentralised systems right through to large urban works. • But of course there are challenges……. 14
CHALLENGES FOR UK IMPLEMENTATION • Temperature – works in Brazil, not used in UK. • Nutrient Removal – will not remove ammonia or phosphorus – but enables effective mainstream N&P recovery. • Dissolved Methane – low gas yield as dissolved at lower temperatures – Membrane degassing needed. 15
Biogas AnMBR MBR Performance feed PST Parameters Unit Permeate Removal% Compliance UASB MBR MT effluent mg L -1 < Detection limit TSS >99 25 mg L -1 41±16 83±7 COD 125 mg L -1 11±7 90±6 BOD 25 N 2 SCOD mg L -1 41±16 - - UASB feed Recirculation • UASB + Membranes allow: • Reduced HRT (smaller reactors) as solids efficiently retained (HRT’s of 4 – 6h possible). • High quality effluent. • But membrane systems require additional energy (& chemicals). 16
ANAEROBIC MBR Anaerobic membrane bioreactor (AnMBR) Deliver 500m³ /d demonstration plant by integrating off-the-shelf UASB, UF membrane and Degassing system. Optimise design and address challenges of wastewater temperature and composition, dissolved methane and biogas management. Two year programme to finalise design and establish performance. 17
INNOVATION NEEDS Urban wastewater strategy Carbon neutral + resource recovery Chemical Energy efficiency Resource recovery Water quality Catchment focus efficiency • openinnovation@severntrent.co.uk
SOME FINAL THOUGHTS • We have a great opportunity in the water industry to transition from energy intensive sewage treatment to energy neutral resource recovery factories • The Resource Recovery & Innovation Centre at Spernal will help us to realise this vision. …open for business 19
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