Municipal Wastewater Discharges - NZ Palmerston North Wastewater Forum 21 April 2017

Alison Lowe

Outline

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1. Municipal wastewater in NZ

2. Types of discharges

• Discharges to water

• High rate application

• Slow rate irrigation – Rotorua and Taupo examples

• Combinations

3. Holistic approach - other considerations

4. Tangata Whenua and Engagement

5. Biosolids

MUNICIPAL WASTEWATER DISCHARGES IN NZ

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330 WWTPs

471M m3/year

18 large WWTPs

392M m3/year

312 smaller WWTPs

80M m3/year

MUNICIPAL WASTEWATER DISCHARGES IN NZ

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Discharges to surface water

Discharges to land

15 of the large plants discharge to water, likely for practical reasons

Only 3 of the 18 large WWTPs discharge to land:

1. 23,700 people Taupo - to land cut and carry

2. 47,500 people Whangarei - to land and water

3. 68,000 people Rotorua - to forested land, considering an alternative

MUNICIPAL WASTEWATER DISCHARGES IN NZ

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Hutt Valley

Whakatane

Waimakariri

Rolleston

Green Island

•

•

Larger City & Community Schemes

Offshore ocean outfalls

Shoreline marine outfalls

Major river outfalls

Major land application

Most treated municipal wastewater

is discharged to the marine environment

through outfalls of one type or another

OFFSHORE OCEAN

OUTFALLS

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Towing HDPE pipes Flexible HDPE pipes absorb wave

motion

Outstanding fatigue resistance

Eg 3 weeks towing 2700 tons from

Norway to Algeria

Dig and Lay, Moving Island

Float and Sink

• Being an island NZ is well served by wastewater

outfalls, especially offshore outfalls

• Global trends and needs are still relevant

• IWA Specialist Outfall Group provides a vehicle for

advancing outfall knowledge and experience

SHORELINE MARINE WATER DISCHARGES

Hastings

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International interest (IWA Symposium) in NZs

RMA investigations and consenting approach

And in specific projects like Hastings ..

Biological Trickling Filter, “no sludge”, offshore

outfall solution developed in conjunction with

tangata whenua

Hastings Biological Trickling Filter

Nature at work - biotransformation

FRESHWATER DISCHARGES

Examples

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Hamilton

Huntly and Ngaruawahia

Palmerston North

Te Awamutu

Discharged water can

flow or be piped to

waterways.

It can enter via discharge

ponds, gabion walls,

pipes with diffusers etc.

Multiport diffuser design

can allow for mixing

zone compliance.

The sensitivity of the

receiving environment

and community

expectations will

influence the design of

the treatment plant.

DISCHARGE VIA WETLANDS

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Engineered Wetlands. Far North, Ruakaka,

St Arnaud, Taumaranui and others Floating Wetlands are growing in number

• Usually improve the treated wastewater quality

• But to a variable and seasonal extent

• Although the water quality can deteriorate as it moves through more open pond type

wetlands .. natural algae and weed growth, bird contamination etc.

The volume of water that enters a wetland also leaves a wetland as a discharge,

plus or minus rainfall / evapotranspiration and seepage.

DISCHARGE TO LAND - HIGH RATE

Cambridge Wetlands & Rapid Infiltration Beds issues

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Wetlands (Foreground) Rapid Infiltration Beds

• Close working relationship between

tangata whenua and Council

• Decided to stop wetlands and RIBs

• Proposal is upgraded treatment, add UV

disinfection and direct river discharge

Site is a difficult one geologically

DISCHARGE TO LAND - HIGH RATE

Rapid Infiltration Beds (RIB)

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• Requires relatively small land area

• Can be an effective means of returning the water to the environment

• NZ examples have developed issues over time

• Very site specific ONLY if soils and groundwater and other factors are suitable

Motueka, but issues with blinding (and rising sea level

Cambridge, but issues with

tomos and lack of capacity

MANAGED AQUIFER RECHARGE

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Not common in NZ but interest

appears to be growing.

Recharge Trial Canterbury

Groundwater Travel 3D

DISCHARGE TO LAND – SLOW RATE IRRIGATION

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Maraetai Kawakawa Bay

Winery, Marlborough

Many matters to consider, e.g.

• A good understanding of the environment

• Groundwater movement

• Soil, effect on soil structure

• Surface water protection

• Typography

• Land use, ownership, long-term availability

• Neighbours, future development

• Potential spray drift, Buffer zones

• Dairy and other industry restrictions

• Generally high costs

Some good news schemes and some not so good

– questions of long term sustainability!

• Requires large land area

• Can maximise nutrient removal “land treatment”

• Can contribute to crop growth

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Taupo – Cut and carry

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• Currently 14-18 mm/wk

• View Rd pivot irrigation - practical

• Rakaunui pop up sprinklers - issues

Benefits

• Efficient nitrogen removal at current

application rate

• Phosphorus stored in soil (not indefinitely)

• Cut and carry revenue offsets costs

• Relatively low tech WWTP

• Conducive to harvesting

Constraints

• Large land area

• Land must be relatively flat

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Taupo – Cut and Carry

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• View Rd currently 380 kg/ha N applied and low N leaching (< 20-30)

• Trial indicates applying > 550 kg/ha would leach >30 (Consent)

• Rakaunui - groundwater DRP appears to be increasing

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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WWTP • Design population 70,000 • Volume 19,000 m3/d Whakarewarewa Forest

• State Forest

• 3.3 km from WWTP

• 120m higher than WWTP

• Soils perfect for irrigation (porous, high P-retention)

• Easement to discharge

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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• 70 mm/wk

• Sprinklers

Benefits

• Land need not be flat

• P stored in soil (not indefinitely)

• Pathogen reduction

Constraints

• Large land area

• Minimal N removal by trees

• WWTP needs to remove N

• High cost

• No revenue from forest crop

• Public excluded from irrigated areas

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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DRP TOX-N NH4-N E coli

g/m3 g/m3 g/m3 /100ml

WWTP discharge 2.2 3.1 0.4 5500

Waipa Stream PRE-LTS 0.04 0.1 0.04 ?

Waipa Stream CURRENT 0.07 1.1 0.06 84

Effect on Waipa Stream

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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Effect on Lake Rotorua – aim to reduce mass load of nutrients

Pre-

LTS

LTS

Design

LTS

1991-2016

LTS

Recent

(2012-16)

Future

t/yr t/yr t/yr t/yr t/yr

N applied - 60 61 40

N uptake by vegetation - 7

Upland denitrification - 12

Wetland denitrification - 16

Load to lake 150 24 28 23* 26-30

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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Bigger picture – Treated wastewater contributes

5% of the nitrogen going to Lake Rotorua

DISCHARGE TO LAND – SLOW RATE IRRIGATION

Rotorua

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• Consent expires 2021

• Land returned to owners

Issues

• Impacting tree health – need to reduce irrigation rate

• Insufficient land to expand

• Impacting pathogens downstream - need to disinfect

• Increasing DRP losses – need to remove P at WWTP

• High operational cost $1.2M/yr

• Increasing public health risk

• Periodically breaching consent to 2012

• Stormflow peaks increasing and exceed WWTP and LTS capacity

• What are the benefits??

• Agreement to identify viable alternatives to Land Treatment

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OTHER CONSIDERATIONS

It’s not just about the discharge…

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GENERIC HOLISTIC APPROACH

FOR WASTEWATER MANAGEMENT

Integrated and Holistic Approaches – The oneness of Nature and Human Nature.

Includes Land Passage in some schemes

WASTEWATER

TREATMENT PLANT

(A Black Box)

INPUTS Energy Chemicals Cost $ Labour

OUTPUTS Sludge Trucks, etc (sludge)

Other residuals

(screening)

Odour/air

emissions

(greenhouse

gases)

Untreated Wastewater

(with Human Waste)

Treated

wastewater

disposal/

discharge and

beneficial reuse

Papatuanuku

passage

Land

Passage

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RMA – “Best Practicable Option”

… best method… having regard to

a) Nature of the discharge and sensitivity of

the receiving environment

b) Financial implications – and effects on

the environment

c) Current state of technical knowledge and

likelihood that the option can be

successfully applied

… or the Best Practicable Combination of Options…

COMBINATIONS AND BENEFICIAL REUSE

Whangarei DC – Ruakaka/Marsden Point

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Offshore ocean outfall in the future

Ruakaka Land Application. Also Council playing

fields irrigation proposal

Marsden Point Oil Refinery – propose beneficial

re-use

COMBINATIONS AND BENEFICIAL REUSE

Whangarei DC – Ruakaka/Marsden Point

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Consider STREAMLINING, OPERABILITY, BEST USE OF

CARBON, NETWORK INTEGRITY, STORMFLOWS,

AFFORDABILITY, ENERGY …

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ENERGY

Is energy neutrality achievable?

Anaerobic digestion remains the best

technology for recovery chemically-bound

energy in wastewater

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RESOURCE RECOVERY

ENERGY

FACTORY

NUTRIENT

FACTORY

WATER

FACTORY

OTHER

PRODUCTS

HEALTH RISK

Quantitative Microbial Risk Assessment (NIWA NZ)

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The Rotorua Steering Group wants the quality of the recovered water:

• clean before it is returned to the environment

• minimise the impact on the environment

• the Mauri improved as much as possible

• support life; safe; can be reused

For the QMRA (bacteria and viruses) we suggested the discharge water:

1. Theoretically safe to swim in undiluted

2. Suitable for unrestricted reuse (not potable)

The QMRA:

1. Found the proposed MBR is sufficient

2. Stated the level of UV required to achieve international std for unrestricted reuse

HEALTH RISK

Quantitative Microbial Risk Assessment (NIWA NZ)

CULTURAL CONSIDERATIONS

Tangata Whenua Cultural Well-Being

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Requirements of the RMA and LGA that address cultural well-being and the linkages to the principles of the Treaty of Waitangi • Water is a ‘taonga’ – treasure

• Holistic approach to physical and spiritual values

• Combining western measurable science with Maori lore / science

Development of an index comparing approach with

- Cultural Monitoring Protocols

- Cultural Health Index (CHI)

TANGATA WHENUA

Working together to develop

options and engage with the wider

community

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Hastings Biological Trickling Filter and

marine discharge

Nature at work - biotransformation

Rotorua earth bed initial concept

ENGAGMENT AND TANGATA WHENUA

Rotorua Future

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• RLC initial scoping report on options (Environmental Court Order)

• Key stakeholders come together and decide on process (LWQS symposium Oct 2013)

TAG (includes RLC and

BOPRC staff)

Project Steering

Committee (Stakeholders)

Cultural Assessment

Sub-Committee

Council Advisors + Business Support

AGREED PROCESS

Independent Chair

Independent Chair

Independent Facilitator

RLC Project Manage

EXTERNAL INPUT

8 Marae visits + 1 Hikoi

28 investigation reports and studies: • Effects of current discharge • Prelimilinary scoping • Development of options • Effects of proposed discharge • Integration of Terax with options

Scion, AWT Water, University of Waikato, Mott MacDonald, PDP, Worley Parsons, Cawthron

Institute, Northcott Research Consultants, BOPRC, Toi Te Ora, RLC, NIWA, Ian Kusabs and Associates,

River Lake Ltd, Far North Environment Lab

Advise Council on preferred option

& Allow for feasible

re-use by community

• Oct 2015 advise Council preferred option, 2016 consult on option

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Wastewater

Flow

Balancing

Secondary

Treatment

MBR

Microfiltration

Bardenpho/

MBR

Tertiary

Treatment

UV

Treatm

en

t

Land

con

tact

be

d

Puarenga Bay

Solids removal Sludge Processing Solid reuse Increase capacity

Stormflow storage/balancing

Full membrane filtration

Phosphorous removal

UV treatment

Water Management

Discharge treated water into a land contact bed before discharge to Puarenga Bay

Consent to allow for the reuse of recovered water

ENGAGMENT AND TANGATA WHENUA

Rotorua Future

ENGAGMENT AND TANGATA WHENUA

Rotorua – Further kōrero on land contact bed

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GOAL – apply for Resource

Consent for WWTP upgrade and

discharge location, having taken into

account all kōrero received from

hapū, iwi and other significant

stakeholders.

While progressing the preferred

option, continue to explore feasibility

of a reuse and discharge option with

hapū / iwi

ENGAGMENT AND TANGATA WHENUA

Rotorua – Land Contact Bed

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Objectives

Integrate cultural elements

involve RPSC, CAS & Mātauranga Māori

experts in the wider engagement with hapū &

iwi

collaborate with Mātauranga Māori experts

with design improvement and indicator

development

To move to a point of collaboration with

identified key stakeholders in order to meet

and address cultural imperatives of this

solution

ENGAGMENT AND TANGATA WHENUA

Rotorua Future – Land Contact Bed initial concept

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BIOSOLIDS

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A new NZ Bio-waste

(Organic) Guideline is

under preparation.

It will supersede the NZ

Biosolids Guidelines

2003

BIOSOLIDS – Dried pellets for land application New Plymouth BioboostTM

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BioboostTM

Dried Pellets

Load out

hoppers

Interior of the gas-fired

barrel drum

BIOSOLIDS – Dried solids for land application

Hutt City Council Plan

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Reduced transport costs

Plan to plough the thermal dried Ab biosolid into soil

BIOSOLIDS – Solar drying

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In “Glasshouse” Drying Halls

Selwyn District Council. NZs newest WWTP

and solar drying facility. Winner of a number of

NZ Awards and finalist in the IWA’s

Sustainability Awards

BIOSOLIDS – Vermicomposting for land application

Rotorua, Hamilton, Maketu

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Sludge mixed with waste pulp fibres Involves joint action of worms and micro-organisms Produces a soil conditioner (vermicast) Ploughed in at time of planting maize fodder crop

BIOSOLIDS – Solids deconstruction

Wetox

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• An R&D project between Wetox and Victoria University of Wellington

• Wet air oxidation process – deconstructs sludge

• Trial on Palmerston North WWTP on alum sludge

BIOSOLIDS – Solids deconstruction

TERAX- Combining anaerobic fermentation & wet oxidation

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Combining these well used technologies means:

• Shorter time cf AD therefore lower capital cost

• 95% destruction cf 50% for AD, so lower disposal costs

• Residual product is fully utilized - No pathogens

BIOSOLIDS – Solids deconstruction

TERAX- Combining anaerobic fermentation & wet oxidation

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Acetic acid

Ammonia

Hi P ash

It’s not just about biosolids…

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Solids are separated from waste water

Waste water sent to WWTP

via sewer

Solids are collected

Sewage or trade waste generated as a mixture of liquid and

solid waste

Solids diverted to sewer – inefficient removal or deliberate

diversion

Biosolids to landfill or land

reuse or resource recovery

Treated water discharged to

environment or recycled water

produced for use in industry and

irrigation

“Front door” waste

“Back door” waste

Organics to digesters / resource

recovery plant

Greenwaste to digesters / resource

recovery plant

Biogas / soil products / bioplastics production

Today’s and Tomorrow’s Waste / Sludge Sewage Interaction

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Thank You