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Wastewater Discharge

Waipukurau and Waipawa

Wastewater Treatment Plants (WWTP)

Community Reference Group

Hamish Lowe 30 August 2018

• LEI – who?

• Wastewater discharge basics

• Previous Investigations• Waipukurau

• Waipawa

Overview

Wastewater discharge

Reticulation Treatment Storage Discharge

Receiving Environment

Water Land

Wastewater discharge

Wastewater discharge

After wastewater has been treated, it needs to be discharged somewhere – it doesn’t just disappear or evaporate.

The options are:

• discharge to land

• freshwater bodies (lakes, rivers, streams)

• estuaries, and

• the ocean.

Wastewater discharge

The soils, terrain and adjacent water bodies determine the most feasible choices.

The use of treatment can assist that choice.

In CHB’s case, there are both land and riveroptions.

Any discharge requires

consideration and balancing

Cultural

Social/ Recreational

Financial

Ecological/ Environmental

Wastewater discharge

Wastewater discharge

What others do

There are 330 council operated wastewater

treatment plants around the country, most

servicing populations <35,000 people.

Smallest caters for 7 households;

Waiotira, Northland;

Largest 1.2 million people; Mangere,

Auckland

Three categories of discharge

• Land (54 M m³ of wastewater per year)

• Water (352 M m³ of wastewater per year)

• Combined land and water (59 M m³ of wastewater per year)

What others do

1%

75%

11%

13%

NZ Wide Treatment Plant Discharges

Unknown Water Discharges Land Discharges Combined Land/Water Discharges

LegendCities>30,000 peopleTowns <5,000 peopleSettlement <750 people

Discharge MethodIrrigation to landRiver/streamOcean

Wastewater discharge

What others do

21%

4%

75%

NZ Surface Water Discharge Methods

River Unknown Ocean

What others do

2%

12%

0%

36%

4%

46%

NZ Land Discharge Methods

Unknown Trees Dairy Grazed Cut & Carry High Rate

Cultural vs tangata whenua

Consider statesWaiora to Waimate

Allows for tapu to noa

Papatuanuku

100 % Land 100 % Water

Irri

gati

on

-H

igh

-rat

e

Irri

gati

on

-N

on

-def

icit

Irri

gati

on

-D

efic

it

Ove

rlan

d -

Ro

ck t

ren

ch

Rap

id In

filt

rati

on

Pip

e to

Wat

er

Ove

rlan

d -

Wet

lan

d

Wastewater discharge

River Wetland Forestry Small Holdings Large Holdings

Are combinations possible or needed?

Water Land

Direct to Water Indirect to Water Stay on Land

Wastewater discharge

Principles of Land Discharge

Land treatment of waste utilises the biological, chemical and physical properties of the land to further treat solid and liquid wastes and/or allow for land passage before reaching the underlying groundwater environment.

Principles of Land Treatment

Land treatment is philosophically and practically distinct from land disposal.

Land treatment seeks to utilise the environment to its

maximum extent treat the waste, and in so doing may

also seek to improve the environment through the

characteristics of the waste.

Land disposal seeks only to dispose of the waste, using the land as a mechanism to allow the waste to enter the environment with limited or

no treatment.

Land Treatment systems

Land Treatment systems

Land - Investigations•How close is the land to the WWTP and how many sensitive neighbours are nearby?Location

•Gentle slopes or flat land at similar height to WWTP are ideal.Terrain and elevation

•Water holding capacity, drainage rate, and particle size or soil type will determine loadings rates.Soil properties

•will wastewater irrigation integrate with the current land use (eg reserve, farm, or forestry) or will the land use need to change to accommodate the wastewater irrigation? How will harvesting or stock grazing regimes integrate with irrigation regimes?

Land use

•how much land is available after subtracting buffers and unsuitable land?Land area

•what are the normal and extreme ranges of rainfall, soil moisture deficit, and wind for each month and year? How will these variations limit irrigation design and operation?Climate

•Cultural, community, societyValues

Land - System design

• Examples are subsurface dripper lines, fixed irrigators, travelling irrigators, border dyke or infiltration basin, and (artificial) wetland basin.

Method of discharge

• Choices are deficit, non-deficit, rapid discharge for disposal to groundwater or wetland, and land passage prior to entering waterways.

Application rate and purpose

• What seasons, weather or soil moisture conditions will restrict or prevent discharges (eg wet soils, heavy rain, or strong winds)?

Timing of discharges

Land - System design

• How much storage volume will be needed? Where will an additional pond be located?

Storage for deferred

discharges

• What will happen to excess wastewater volumes and what limits would be appropriate?

Emergency or large storm

contingencies

Land - System design

In developing a land discharge system there are a series of basic design parameters which need to be considered.

Basic design parameters:Cultural acceptability

Hydraulic Loading

Organic Loading

Nutrient Loading

Pathogen Loading

Principles of Water Discharge

Discharge at a rate and composition that is within the seasonal assimilative capacity of the waterway.

Water - Investigations•How close is the land to the WWTP to the waterwayLocation

•Fast flowing, slow movingCharacteristics

•How does flow go up and down and how does this match wastewater flowsFlow seasonality

•Contact recreation, stock waterWater use

•What is the level of nutrient enrichment existing and can more be accommodatedChemical status

•What lives there – macroinvertebrates, fish, algaeBiological status

•Cultural, community, societyValues

Water - System design

• Direct, indirect – pipe, near bank, galleryMethod of discharge

• Is it culturally acceptable and will nutrient enrichment influence quality and habitat

What is the impact

• How is volume and treatment level adjusted to reflect flow and limitations

Timing of discharges

Water - System design

• Can storage be used to avoid low flow discharges?

Storage for deferred

discharges

• What will happen to excess wastewater volumes and what limits would be appropriate?

Emergency or large storm

contingencies

Water - System design

In developing a water discharge there are a series of basic design parameters which need to be considered.

Basic design parameters:Cultural acceptability

Hydraulic Loading

Organic Loading

Nutrient Loading

Pathogen Loading

CLAWD

• What criteria will be used to determine when the best times will be to discharge to these environments and how much is to be discharged each day? How will they be prioritised and balanced?

Criteria for selecting Combined Land and

Water Discharges

• How much storage volume will be needed for times when neither environment (land and water) can receive the discharges? Where will an additional pond be located?

Storage for deferred discharges

• What will happen to excess wastewater volumes and what limits would be appropriate?

Emergency or large storm contingencies

Benefits and Opportunities

Community should decide

Can it be expanded

One system or multiple

Is water a resource

Previous investigations

• Irrigating the existing quality effluent on to forests that had been planted by the Regional Council at Waipawa and Waipukurau.

• Storing effluent when the forests were not capable of accepting the spray irrigation.

• Discharging excess stored effluent into the Tukituki and Waipawa Rivers at times when the river flows were 3 times the median flow.

In 2007 the Hawke’s Bay

Regional Council and

CHBDC together investigated a

forest treatment

option. This consisted of:

Waipukurau

Image Credit: Sarah Platt

Waipukurau

Waipukurau

Waipukurau

Waipawa

Image Credit: Sarah Platt

Waipawa

Waipawa

Waipawa

Waipawa

Your choice

Water

Land

www.lei.co.nz | Palmerston North Christchurch Wellington | office@lei.co.nz

Advice AEE Agricultural Analysis Application Approachable Assessments Assimilation Assistance Biosolids Capability Client Communications Communities Compliance

Compost Consents Consultation Contamination Coordinate Council Cultural Current Data Degradation Design Detention Developments

Discharges Documentation Drafting E. coli Ecosystems Effects Engagement Environment Equipment Evidence Excellence Experienced Expert Facilitating Farming Feasibility

Fieldwork First-flush Fit-for-purpose Flooding Fun Geology Graphs Greywater Groundwater Guidelines Handbag Hazardous Hydraulics Innovation Interpretation Investigation

Irrigation Land Landfills Landscape Land-treatment Leaching LodgeManagement Metals Microbiology Modelling Monitoring

NES Nitrogen Nutrients Onsite Optimisation Organics Overseer Papers Pathogens Phosphorus Plain-english Plans Preparation Presentations

Project Quality Relevant Remediation Reports Research Review Sampling Scientific Septage Sludge Soil Solutions Spreadsheets Standpipes Stormwater Strategy

Support Surface Water Sustainability Systems Team Testing Timely Treatment Validation Wastewater Water Water-balance Waterways