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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