inlet screen and screenings handling plant … zone documents/e...inlet screen and screenings...

HUBER Technology UK – www.huber.co.uk

INLET SCREEN AND SCREENINGS HANDLING PLANT SELECTION CONUNDRUMS

PRESENTED BY: DALE FOSTER – AREA MANAGER

It has to be understood that a well performing screening process can have

significant impacts on final effluent quality, treatment plant capacity, operator

morale and OPEX.


FAKE NEWS

After reviewing current water company activities OFWAT have strongly recommended that ALL companies adopt The Water Industry Mechanical and Electrical Specifications (WITHOUT AMENDMENTS or ADDITIONS) that define the requirements for a wide range of mechanical and electrical equipment used in the UK water industry.

This they say would drive significant cost savings into the delivery of projects in future AMP periods, allowing the supply chain to provide harmonised solutions for all. This should result in a noticeable reduction in water bills for customers.

One supplier interviewed said “We thought utopia had arrived when the Pump Centre, along with most Water Companies developed these specifications. However, we were not surprised when very quickly every company issued reams of additions and amendments making the standardisation of solutions throughout the water industry impossible.”


Another supplier commented: “All the equipment we provide is WIMES compliant, but we rarely sell anything of this ilk without having to tweak something or other. Unless we’re mistaken all the equipment that goes into the water industry is designed to do the same job regardless of which water company it ends up in, so why does everything end up being customised for each end user?”

On the back of this announcement, OFWAT also commented about the influence that water company asset standards, which can differ significantly, have on costs within the industry. Their spokesperson said “If we take wastewater treatment as an example, each company has its own asset standard relative to the selection of inlet screening plant. However, with research carried out on these products and their application, why do these asset standards vary when the equipment in question is asked to do the same job regardless of its geographic location?”

FAKE NEWS


Lastly, OFWAT expressed some concern over the possibility that apparently £m’s is spent by water companies during a typical AMP period on investigation work to determine the best outcome for identified schemes. They added “Although some of this is justifiable, particularly on very large schemes, it seems that a portion of this investigation work might well be avoided or reduced if in the digital world the end user managed and maintained the data provided by contractors, suppliers, manufacturers and service providers far better than they currently do.”

FAKE NEWS



Examples of Water Company Asset Standards and references to

WIMES Documents:

“In addition, any Inlet Works project shall be designed in

accordance with the relevant Water Industry Mechanical and

Electrical Specifications (WIMES). These would include (but

would not be limited to) the following:

� WIMES 2.02 Grit Removal and Treatment Equipment

� WIMES 2.03 Package Inlet Works for Wastewater Treatment

� WIMES 5.03 Screens for Sewage Treatment

� WIMES 5.04 Overflow Screens for Sewerage Systems and

STW

� WIMES 6.03 Screenings Handling Equipment”


INLET SCREEN AND SCREENINGS HANDLING PLANT SELECTION CONUNDRUM

SPECIFICATION

“The technical requirements for the inlet screens shall be as

described in Water Industry Mechanical & Electrical Specification

WIMES 5.03 ‘Screens for Sewage Treatment’ as published by

The Pump Centre, ESR Technology, with revisions and additions

as detailed here and in the project specification.

REVISIONS & ADDITIONS TO SPECIFICATION WIMES 5.03ISSUE X, 200?

•Revised clauses that replace or update WIMES 5.03 clauses

are suffixed (R)”


THE NEED FOR ROBUST ASSET STANDARDS


THE NEED FOR ROBUST ASSET STANDARDS

Inlet works are the workhorse of any wastewater treatment plant.

� Challenged and updated when new technologies or testing of

equipment provide opportunities for change.

More importantly, once a new or upgraded works is operational planned, preventative maintenance plans should be implemented immediately.

Training and maintenance is paramount to realise the intended aims of asset standards and associated specifications.

Asset standards should reflect this and ideally be:

� The minimum acceptable standard.

� As robust as is affordable.

� Based on sound experience and empirical information.

� Backed up by available proof that ineffective plant in this area of

treatment results in significant increase in OPEX costs

elsewhere in the process.



Examples of Asset Standard incorporated or associated Water Company documents:

� Water company specific engineering specifications.� Hydraulic specifications.� DSEAR requirements.� British standards / EU directives. � Deviation policies and decision trees. � Testing, commissioning and performance testing. � Blinding factors.� Approach channel, aperture and downstream velocities.� Headlosses and hydraulic calculation spreadsheets (possibly with one

manufacturer in mind).� Screenings capture rates. � Screenings transfer and handling specifications. � Peak screenings loading rates and calculation spreadsheets.� Material requirements.� Standard channel widths and screen lengths.

And many more, but are there any gaps?



I cover 4 water companies and Asset Standards have varying

requirements in many of the areas listed.

So, what does this mean?



Uncertainty: � Do we have the latest documents?

� Chasing the vendor for completed WIMES data sheets.

Time: � Collating the necessary documents from various sources.

� Verifying the information is current.

� Understanding the nuances of each water company’s requirements.

� Sometimes educating the contractors in understanding the relevant standards and ensuring we receive the necessary information.

� Appraising the contractors own contractual clauses versus the client’s asset standards.

Pressure: � To quickly turn round proposals with missing/ambiguous information.

� To ensure our submissions explain the detailed nuances relative to the client’s requirements to allow accurate appraisal and comparisons.

This often results in the selection of different screens and screenings handling plant dependent upon which water company it is.



Example: New build, elevated inlet works for a maximum flow of 266 l/s & a P.E. of 18,000 requiring fine screens, launder and screenings handling plant. Water Company A Inlet Screen selection (or closest available):

Data

Flow rate Q 266 l/s

Channel width 1200 mm

Selected screen width w 952 mm

Screen length L 6000 mm

Upstream step s 200 mmDownstream water level hu 750 mm

Downstream flow velocity vu 0.30 m/s

Validated flow through rear panel 266.0 l/s

Validated flow through front panel 266.0 l/s

Calculation criteria

Mesh perforation size e 6.0 mm

Installation angle α 60°

Blinding factor, front panel Bf2 60%

Mesh open area f 51%

Discharge coefficient Cd 0.62

49 mm 251 mm 300 mm 1050 mm 1.38 m/s 0.26 m/s

Hole velocity

(blinded)**

Headloss,

front panel ∆h2

Headloss, rear

panel ∆h1

Total

headloss*, ∆h

= ∆h1 + ∆h2

Upstream

water level, ho

= hu + ∆h

Upstream flow

velocity, vo



Example: New build, elevated inlet works for a maximum flow of 266 l/s & a P.E. of 18,000 requiring fine screens, launder and screenings handling plant. Water Company B Inlet Screen selection:

Data

Flow rate Q 266 l/s














60 mm 167 mm 227 mm 977 mm 1.12 m/s 0.30 m/s

Headloss, rear

panel ∆h1

Total

headloss*, ∆h

= ∆h1 + ∆h2

Upstream

water level, ho

= hu + ∆h

Upstream flow

velocity, vo

Hole velocity

(blinded)**

Headloss,

front panel ∆h2



Example: New build, elevated inlet works for a maximum flow of

266 l/s & a P.E. of 18,000 requiring fine screens, launder and

screenings handling plant. Water Company A followed by Water Company B Screenings Handling Plant selection:

Water Company A applies a peak factor of 70 = Predicted peak

screenings load of 1.6 m3/hour.

Water Company B applies a peak factor of 80 (reason

unexplained) = Predicted peak screenings load of 1.8 m3/hour.

Water Company A will accept 2 m3/hour duty/standby screenings

handling plant.

*Water Company B will not accept 2 m3/hour duty/standby

screenings handling plant due to capacity being too close to

predicted peak screenings loading. *Some water companies would permit a smaller screenings handling plant operated via VSD’s at peak times, some wouldn’t.



� Some water companies would require duty only screenings

handling plant for 18,000 P.E. site.

� Some would require compactors with no washing involved.

� Different requirements for hydraulic “freeboard” in screen

channels.

� Views differ relative to hand raked or free bypass channels.

� At lower flows hydraulic outputs for Escalator type fine screens

“do not compute” and combined screens could be a more

appropriate selection.

� Combined screens usually precluded due to screen selection

based on P.E. of site and perceived lower SCR and screenings

processing capacity.

� Numerous other differences have to be digested and noted by

equipment providers; materials of construction, capacity

thresholds etc. etc. etc.



� Inlet screens are sized on maximum flow arriving at the works. � Screen hydraulic outputs need to meet asset standard at maximum flow. � What happens at lower than maximum flow and what %age screen blinding

rates should be applied in this scenario? Data

Flow rate Q 150 l/s














17 mm 120 mm 137 mm 887 mm 0.95 m/s 0.18 m/s

Headloss, rear

panel ∆h1

Total

headloss*, ∆h

= ∆h1 + ∆h2

Upstream

water level, ho

= hu + ∆h

Upstream flow

velocity, vo

Hole velocity

(blinded) **

Headloss,

front panel ∆h2



Data

Flow rate Q 150 l/s














17 mm 26 mm 42 mm 792 mm 0.44 m/s 0.21 m/s

Headloss, rear

panel ∆h1

Total

headloss*, ∆h

= ∆h1 + ∆h2

Upstream

water level, ho

= hu + ∆h

Upstream flow

velocity, vo

Hole velocity

(blinded) **

Headloss,

front panel ∆h2



� Screenings removal rates for screens can be contentious.

� Little mention in some asset standards.

� Belt speed metres/minute – Thickness of screenings layer x

mm – Capacity per metre belt width = x m3/hour.

� There are formulas to calculate this in some asset standards

based on one manufacturers screens.

� Some formulas do not mention operating screens via VSD’s to

increase screenings removal rates.

Influencing factors:� Angle of screen installation.

� Number of rakes/tines located between the screen elements.

� Blinding factor applied.

� Screen width.

� Belt speed.

� Thickness of screenings layer – Guidance?



When screenings handling plant is specified to replace existing kit

whilst old screens are retained:

� Volume of screenings the screens can remove sometimes

seems irrelevant.

� New screenings handling plant can have far larger volumetric

throughput than the screens can remove.

Problems can lay elsewhere.

1. Inefficient screen performance which when upgraded

improves.

2. Poor washwater to screens, launder and screenings handling

plant.

3. Poor launder design and plant layout.

4. Poorly designed launder stone traps.

5. Poor management of flows and loads arriving at the works.



Screenings transport systems – Launders/Screw Conveyors.

� Fall within launder often mentioned.

� Rarely a mention about exact feed arrangement to

duty/standby or multiple screenings handling units.

� Vital when screens are elevated feeding a launder system.

� Rarely a mention about creating good hydraulic conditions with

a launder relative to velocity/diameter of launder/volume of

launder water.

� Launders often made to suit discharge dimensions of

screen(s).

� Stone traps – Yes/No?



Cleanliness of screenings.

� Sometimes mentioned, sometimes given a broad ranging

descriptive of “screenings must not contain visible faecal matter

and be odour free”……………..or something similar.

� Testing of screenings handling plant was undertaken at

Netheridge STW as part of a UKWIR project.

� Not really sure the industry “gets it”.

In my opinion, landfilling dirty screenings is a waste of valuable

resources. Methane from biodegradable waste decomposing in

landfills is a potent greenhouse gas.

Methane from landfills accounts for a significant portion of UK

methane emissions. Methane is claimed to be 23 times as

powerful a greenhouse gas as carbon dioxide.


POOR INLET WORKS DESIGN LEADS TO……..

� Compromised performance of grit systems, settlement tanks, pumps and valves, all of which impact on the performance, reliability and increased OPEX of downstream Plant.

� 30-40% increase in plant power bills, plus £1000’s for operator intervention.

� Less biogas generation and unstable digester performance - Primary sludge very valuable for digestion & its potential to generate biogas is much higher than biological sludge.

Screenings passing through the system can lead to: � Problems with sludge processing equipment (thickeners) which can

compromise sludge storage.� More sludge being held on the secondary process = Too high mixed liquor

concentrations = Sludge blankets rising and higher quantities of solids passing forward to tertiary treatment = Higher levels of back washing =Costs and consents may also be compromised.

� Screenings entering digesters = ragged up heat exchangers = loss of heat generated in the digester = burning natural gas to supplement the system =HIGHER OPEX AND “CHALLENGED” PROCESSES


POOR INLET WORKS DESIGN LEADS TO……..

� Much has been done by the water companies over the years to try to reduce

the number of gross solids being discharged to sewer, i.e.. “bag it and bin it”

“love every drop” initiatives.

� Sadly, Mr. & Mrs. Joe Public’s initiative is generally “FLUSH IT AND

FORGET IT.” – That is why it is vital to ensure inlet works are properly

designed and maintained.


BARRIERS TO APPLYING BEST PRACTICE

�Use of existing channels driven by resultant CAPEX not always

best solution.

�Cutting corners leads to under resilient plant, lack of operational

confidence, increased downstream OPEX.

�Lack of site data.

�Poor understanding of relevant standards in the supply chain.

�CAPEX incentivised Contracts with the Delivery Partners.

�Procurement process can divorce suppliers from Operations.

Operations = key role in identifying existing issues, site

specific/catchment characteristics and providing historical

information on the plant.


INLET WORKS EQUIPMENT DESIGN - A SUPPLIERS PERSPECTIVE

In 2009 I presented at a EWWM Conference extolling the virtues

of “good design of inlet works.” At that time Water Company Asset

Standards were fairly robust (still are!) but I did stress that the

lack of maintenance devalued the advances and benefits that

these improvements had made. Hopefully the TOTEX approach

will allow more focus on this topic?

Is this really the case in 2018?

I’ll let you be the judges ☺


Sewerage Network Screening Solutions -

CSO’s/Emergency Overflows/Pumping Station Overflows.

Screening protection for Wastewater Pumping

Stations.

Inlet Works Coarse & Fine Screening & Screenings

Processing – Medium/Large P.E. Works.

Inlet Works Screening & Screenings

Processing – Small P.E. Works.

Packaged Inlet Works - Medium P.E. Works.

Packaged Inlet Works – Small P.E.

Works.

Stormwater Overflow Treatment

at Inlet Works.

OUR PRODUCT PORTFOLIO FOR PRELIMINARY & PRIMARY TREATMENT

Ultra Fine Screens – To

increase settlement capacity

instead of new P.S.T.’s or to

protect sensitive downstream

processes such as SBR/BAFF

etc.

Grit Treatment Plant – Classification,

Washing & Recycling.


Sludge Treatment Import Screens

Thickening

Dewatering

Low-Medium Temperature Sludge Drying.

OUR PRODUCT PORTFOLIO FOR SLUDGE TREATMENT


• THERMWIN & ROWIN SYSTEMS

• Heat recovery from wastewater for heating & cooling buildings.

• ADVANCE & ANAEROBIC DIGESTION

• Equipment to enhance the digestion process - Grit & plastics removal to PAS110.

• Digestate dewatering.

• BIOWASTE PROCESSING

• Solids & grit removal.

• SLUDGE2ENERGY

• GREEN BUIDLING SOLUTIONS

OUR PRODUCT PORTFOLIO FOR WASTE2ENERGY


• INDUSTRIAL Full range of:

• Screens• Solids handling

• DAF plant

• Sludge thickening dewatering and drying

• Water reuse solutions

OUR PRODUCT PORTFOLIO FOR THE INDUSTRIAL SECTOR


THANK YOU FOR YOUR ATTENTION

Huber Technology UKUnits C&D Brunel ParkBumpers Farm Industrial EstateChippenhamWiltshire - SN14 6NQ

Tel. +44 (0)1249 765000 Fax +44 (0)1249 449076eMail [email protected] www.huber.co.uk

Dale Foster Huber Technology07980 316059 [email protected]