Pahiatua WWTP discharge to the Mangatainoka River May 2017 Dr. - - PDF document

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Pahiatua WWTP discharge to the Mangatainoka River

May 2017

• Dr. Olivier Ausseil

Aquanet Consulting Ltd

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Pahiatua WWTP – Current discharge Point and Monitoring Sites

Pahiatua WWTP Town Creek (Current discharge) Pukemiku Stream Upstream Pahiatua WWTP Downstream Pahiatua WWTP

Current.

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Pahiatua WWTP – Monitoring Sites

Upstream monitoring

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Pahiatua WWTP – Town Creek Data

Upstream monitoring DRP (mg/l) SIN (mg/l) Ammoniacal- N (mg/l)

• E. coli

(/100mL) Date u/s d/s u/s d/s u/s d/s u/s d/s 18 April 2017 0.035 0.314 1.93 2.31 0.028 0.085

• 21 April

2017 0.036 0.297 2.07 2.37 0.030 0.101 480 390 24 April 2017 0.035 0.329 1.98 2.34 0.023 0.144 130 260

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Instream Water Quality – Ammoniacal Nitrogen

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S All Flows > 20th FEP < 20th FEP Median - 20th FEP < Median Half Median

• Median

< Half Median Total ammoniacal-N (g/m³)

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Instream Water Quality – Ammoniacal Nitrogen (NPSFM)

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Median unionised ammoniacal nitrogen (ppb) For 12-month period ending Upstream Downstream

A B

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Instream Water Quality – Ammoniacal Nitrogen (NPSFM)

20 40 60 80 100 120 Maximum unionised ammoniacal nitrogen (ppb) For 12-month period ending Upstream Downstream

A B C D 8

Instream Water Quality – E.coli

1 10 100 1,000 10,000 U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S All Flows > 20th FEP < 20th FEP Median - 20th FEP < Median Half Median

• Median

< Half Median E.coli (MPN/100mL)

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Instream Water Quality – DRP

0.00 0.01 0.02 0.03 0.04 0.05 0.06 0.07 U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S All Flows > 20th FEP < 20th FEP Median - 20th FEP < Median Half Median

• Median

< Half Median DRP (g/m³)

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Instream Water Quality – SIN

0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S All Flows > 20th FEP < 20th FEP Median - 20th FEP < Median Half Median

• Median

< Half Median SIN (g/m³)

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Instream Water Quality – SIN:DRP ratios

10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 1 10 100 1000 SIN/DRP

Mangatainoka Upstream WWTP

10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 1 10 100 1000 SIN/DRP River Flow (L/s)

Mangatainoka Downstream WWTP

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Pahiatua WWTP – Nutrients

Upstream monitoring

Current situation DRP SIN Daily load (kg/day) 1.0 1.9 In river concentration increase (mg/l) (indicative %

• f One Plan

target) Mean Annual Flow 0.0007 (7%) 0.002 (0.6%) Summer low flow (Half median flow) 0.0016 (16%) 0.004 (0.8%) Extreme summer low flow (MALF) 0.0044 (44.2%) 0.010 (2.4%)

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Periphyton

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Periphyton – Chlorophyll a

20 40 60 80 100 120 140 160 180 200 Chlorophyll a (mg/m2) Upstream Downstream No data

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Periphyton – Visual Surveys

10 20 30 40 50 60 70 80 90 Long Filamentous (% cover) Upstream Downstream No data

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Periphyton – Visual Surveys

20 40 60 80 Thick Mats (% cover) Upstream Downstream No data 20 40 60 80 Cyanobacteria cover (%) Upstream Downstream No data

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Macroinvertebrate Communities

Snails Worms Stoneflies Mayflies

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Macroinvertebrate Communities

20 40 60 80 100 120 140 MCI Upstream Downstream 1 2 3 4 5 6 7 QMCI Upstream Downstream

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Instream Water Quality – POM

1 2 3 4 5 6 U/SD/S U/SD/S U/SD/S U/SD/S U/SD/S U/SD/S U/SD/S All Flows > 20th FEP < 20th FEP Median - 20th FEP < Median Half Median - Median < Half Median Particulate Organic Matter (g/m³)

Post-upgrade – improvements and effects

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Instream Water Quality – Dissolved Oxygen

20 40 60 80 100 120 140 U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S U/S D/S All Flows > 20th FEP < 20th FEP Median - 20th FEP < Median Half Median

• Median

< Half Median DO (% saturation)

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Instream Water Quality – Dissolved Oxygen

20 40 60 80 100 120 140 160 180 DO (% saturation) Upstream Downstream

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Instream Water Quality – Dissolved Oxygen

• Background to One Plan target (80% saturation)
• Existence of current issue associated with discharge unknown
• Monitoring options
• Dawn spot measurements during low flows
• Continuous DO
• Assessment of data
• Any difference between upstream and downstream in spot data?
• If difference, continuous monitoring
• Any difference
• If difference, likely significance to aquatic life

Post-upgrade – improvements and effects

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Effect/Value Contamnt Current effect from the discharge Post-upgrade effect from the discharge Contact recreation, Stock water E.coli Possible reduction in % time meeting target (Role of discharge unclear) UV treatment No more than minor Periphyton (Recreation, trout fishery, life supporting capacity) DRP Significant increase in DRP concentration 3 fold reduction SIN Not significant on SIN concentration Unlikely to drive periphyton growth Similar or reduced Periphyton Mild increase downstream, One Plan target just met/marginally exceeded Reduced effect associated with DRP reduction Macroinvertebrates (life-supporting capacity, trout fishery) Ammonia, POM, DRP/SIN (via periphyton) Minor, One Plan target always met Minor, One Plan target always met DO (life-supporting capacity, trout fishery) DRP/SIN (via periphyton) Unknown, but likely to be less than 1.5km upstream Reduced effect associated with periphyton reduction