5/25/2017 Pahiatua WWTP discharge to the Mangatainoka River May 2017 Dr. Olivier Ausseil Aquanet Consulting Ltd 1 Pahiatua WWTP – Current discharge Point and Monitoring Sites Current. Downstream Upstream Pahiatua WWTP Pahiatua WWTP Pukemiku Stream Town Creek (Current discharge) Pahiatua WWTP 2 1
5/25/2017 Pahiatua WWTP – Monitoring Sites Upstream monitoring 3 Pahiatua WWTP – Town Creek Data Upstream monitoring DRP SIN Ammoniacal- E. coli (mg/l) (mg/l) N (mg/l) (/100mL) Date u/s d/s u/s d/s u/s d/s u/s d/s 18 April 0.035 0.314 1.93 2.31 0.028 0.085 - - 2017 21 April 0.036 0.297 2.07 2.37 0.030 0.101 480 390 2017 24 April 0.035 0.329 1.98 2.34 0.023 0.144 130 260 2017 4 2
5/25/2017 Instream Water Quality – Ammoniacal Nitrogen 0.45 0.40 0.35 0.30 Total ammoniacal-N (g/m³) 0.25 0.20 0.15 0.10 0.05 0.00 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 - < Median Half Median < Half 20th FEP - Median Median 5 Instream Water Quality – Ammoniacal Nitrogen (NPSFM) Median unionised ammoniacal nitrogen 1.4 B 1.2 1.0 0.8 A (ppb) 0.6 0.4 0.2 0.0 Upstream Downstream For 12-month period ending 6 3
5/25/2017 Instream Water Quality – Ammoniacal Nitrogen (NPSFM) 120 Maximum unionised ammoniacal D 100 nitrogen (ppb) 80 60 C 40 20 0 B A Upstream Downstream For 12-month period ending 7 Instream Water Quality – E.coli 10,000 E.coli (MPN/100mL) 1,000 100 10 1 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 - < Median Half Median < Half 20th FEP - Median Median 8 4
5/25/2017 Instream Water Quality – DRP 0.07 0.06 0.05 DRP (g/m³) 0.04 0.03 0.02 0.01 0.00 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 - < Median Half Median < Half 20th FEP - Median Median 9 Instream Water Quality – SIN 2.0 1.8 1.6 1.4 SIN (g/m³) 1.2 1.0 0.8 0.6 0.4 0.2 0.0 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 - < Median Half Median < Half 20th FEP - Median Median 10 5
5/25/2017 Instream Water Quality – SIN:DRP ratios Mangatainoka Upstream WWTP 1000 SIN/DRP 100 10 1 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 Mangatainoka Downstream WWTP 1000 SIN/DRP 100 10 1 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 River Flow (L/s) 11 Pahiatua WWTP – Nutrients Upstream Current situation DRP SIN monitoring Daily load (kg/day) 1.0 1.9 Mean Annual 0.0007 0.002 Flow (7%) (0.6%) In river concentration Summer low 0.0016 0.004 increase (mg/l) flow (Half (16%) (0.8%) (indicative % median flow) of One Plan Extreme 0.0044 0.010 target) summer low (44.2%) (2.4%) flow (MALF) 12 6
5/25/2017 Periphyton 13 Periphyton – Chlorophyll a 200 180 Chlorophyll a (mg/m2) 160 140 120 100 80 60 40 20 0 Upstream Downstream No data 14 7
5/25/2017 Periphyton – Visual Surveys 90 80 70 Long Filamentous (% cover) 60 50 40 30 20 10 0 Upstream Downstream No data 15 Periphyton – Visual Surveys 80 Thick Mats (% cover) 60 40 20 0 Upstream Downstream No data 80 Cyanobacteria cover (%) 60 40 20 0 Upstream Downstream No data 16 8
5/25/2017 Macroinvertebrate Communities Snails Worms Stoneflies Mayflies 17 Macroinvertebrate Communities 140 7 120 6 100 5 80 4 MCI 60 QMCI 3 40 2 20 1 0 0 Upstream Downstream Upstream Downstream 18 9
5/25/2017 Instream Water Quality – POM 6 5 Particulate Organic Matter (g/m³) 4 3 2 1 0 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 - < Median Half < Half 20th FEP Median - Median Median 19 Post-upgrade – improvements and effects 20 10
5/25/2017 Instream Water Quality – Dissolved Oxygen 140 120 DO (% saturation) 100 80 60 40 20 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 - < Median Half Median < Half 20th FEP - Median Median 21 Instream Water Quality – Dissolved Oxygen 180 160 140 DO (% saturation) 120 100 80 60 40 20 0 Upstream Downstream 22 11
5/25/2017 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 23 Post-upgrade – improvements and effects Current effect from the Post-upgrade effect from Effect/Value Contamnt discharge the discharge Contact recreation, E.coli Possible reduction in % time UV treatment Stock water meeting target No more than minor (Role of discharge unclear) Periphyton DRP Significant increase in DRP 3 fold reduction (Recreation, trout concentration fishery, life supporting SIN Not significant on SIN Similar or reduced capacity) concentration Unlikely to drive periphyton growth Periphyton Mild increase downstream, Reduced effect associated One Plan target just with DRP reduction met/marginally exceeded Macroinvertebrates Ammonia, POM, Minor, Minor, (life-supporting DRP/SIN (via One Plan target always met One Plan target always met capacity, trout fishery) periphyton) DO (life-supporting DRP/SIN (via Unknown, but likely to be less Reduced effect associated capacity, trout fishery) periphyton) than 1.5km upstream with periphyton reduction 24 12
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