Reduction of clogging in agricultural irrigation networks

Transcription

1 Reduction of clogging in agricultural irrigation networks IRTA Torre Marimon Carmen Biel Robert Savé CTM Montse Calderer Gemma Serra Re-Water Congress November 2-3, 2015

2 Introduction Biofilms can have important implications in horticultural situations. Also are likely present in every water system and pipe, filter, pump, tank, hose, emitter and nozzle in a nursery, greenhouse, field crop, garden, etc. Not surprisingly, biofilms are also commonly associated with irrigation systems where they can cause a variety of problems including clogging and corrosion. Emitter clogging is one of the bottlenecks to restrain the application and popularization of reclaimed water with drip irrigation technology. It is tightly related to the formation of biofilms attached on drip irrigation pipes and emitters. Biofilm formation in the emitter depends on design, water flow velocity, water pressure. 2

3 Objectives One objective of present assay is testing the standard maintenance cleaning of irrigation system with nitric acid against a novel system based on the injection of CO 2 in the water. Second objective is to compare two drippers with different hydraulic properties because its design and internal path. 3

4 Tested treatments - Reclaimed water from ETAP Caldes de Montbui (Barcelona) - Reclaimed water + Nitric Acid - Reclaimed water + CO 2 injection - Well water = water from underground extracted from the same plot IRRIGATION DRIPPERS Compensated dripper integral dripper line 4

5 Emitters with different hydraulic properties Pressure compensated dripper model PCJ Junior Integral line dripper model Uniram RC Netafim Israel (Image from: web) Water passages dimensions (width x depth x lenght) Pressure compensate 1.03x0.75x35 mm Integral line 1.26x0.95x40 mm Filtration area 2 mm mm 2 5

6 Reclaimed water origin WWTP Caldes de Montbui Contracting body: Consorci per a la Defensa del Besós Working load: 6000 m 3.day -1 Population: inhabitants Treatments: Remove fats, remove sand, homogeneisation Primary treatment: Decanting Secondary treatment: Activated sludge Drying: Filter 6

7 Irrigation water quality characteristics Water quality parameters Underground water Reclaimed Water Electric Conductivity 25ºC (ds.m -1 ) ph Bicarbonate (mg.l -1 ) Carbonates (mg.l -1 ) Nitrate (mg.l -1 ) Phosphorus (µg.l -1 ) Potassium (mg.l -1 ) Calcium (mg.l -1 ) Magnesium (mg.l -1 ) Sodium (mg.l -1 ) Sulfate (mg.l -1 ) Chloride (mg.l -1 ) Boron (mg.l -1 ) Copper (mg.l -1 ) 0 0 Iron (mg.l -1 ) 0 0 Fluoride (mg.l -1 ) Manganese (mg.l -1 ) 0 0 Zinc (mg.l -1 )

8 Reclaimed water origin WWTP Caldes de Montbui 27 m 3 By tractor+tank (7000 L) 8

9 Experimental design and pipes distribution Water treatments Reclaimed water Reclaimed water + Nitric acid Reclaimed water +CO 2 injection Underground water Emitters Integral dripper line Pressure compensated dripper 8.5 m 16 m

10 Experimental design Dripper s nominal water flow rate is 2 L.h -1 at working pressure: 1.4 and 1.8 kg.m -2 Type of operation: Irrigation during 10 minutes x 2 times a day at 9:00 and 16:00 hours. The water is stagnant from 9:10 to 16:00 h and from 16:10 to 9:00 h of the following day. 10

11 Experimental design Irrigation control room and tanks for CO 2 injection and acid application to water Automatic control panel for irrigation schedule and CO 2 injection Tanks for reclaimed water and one with CO 2 injection (right tank). 11

12 Nitric acid injection to the irrigation pipes Pressure control Dosatron (for accurately dose a liquid into water) Nitric acid solution Nitric acid diluted on the water through a venturi system (Dosatron International SAS, France), 12

13 Measurement at irrigation pipes ph measurements Watermeter Emitter water flow Water pressure evaluation 13

14 Sampling schemes Emitter Flow rate samling Emitter Integral dripper line Biofilm formation sampling Sample 1 Sample 2 Sample 3 Tram A Tram B 14

15 Biofilm sampling 1. Sample collection: pipe sections will be monthly collected and transported to the laboratory in insulated cold boxes and sterile bottles. FOR EACH PIPE: 3 SUBSECTIONS Section a Section b Section c 2. Swabbing: Each pipe will be cut into three portions and biofilm will be collected by swabbing the surface. 3. Bacteria extraction: Vortexing vigorously the swab to release the bacteria into the sterile solution (Ringer ¼ ). 4. Heterotrophic plate count (HPC) method: The number of heterotrophic bacteria in each sample will be counted on R2A Agar. Each sample was tested in duplicate and colonies were counted after incubation at 22ºC for 7 days. 1ml 1ml 1ml 5. Results: concentration per unit area of the pipe surface. Original

16 ph Results : water ph evolution RW RW+CO2 RW+NO3 WW Stop due to wind storm damages /09/ /11/ /01/ /04/ /06/ /08/ /10/2015 Days 16

17 Electrical conductivity (ds.m -1 ) Results: Electrical conductivity Electrical conductivity evolution RW RW+CO RW+NO3 WW /07/ /07/ /08/ /09/ /09/ /10/ /11/

18 Effect of reclaimed water storage in chemical parameters Water quality parameters 26/6/15 31/07/ /09/2015 Electrical Conductivity 25ºC (ds.m -1 ) ph Bicarbonate (mg.l-1) Carbonates (mg.l-1) Nitrate (mg.l-1) Phosphorus (µg.l -1 ) Potassium (mg.l-1) Calcium (mg.l-1) Magnesium (mg.l-1) Sodium (mg.l-1) Sulfate (mg.l-1) Chloride (mg.l-1)

19 Water quality parameters comparision between maintenance treatments Water quality parameters RW RW+CO 2 RW+NO 3 WW Electrical Conductivity 25ºC (ds.m -1 ) ph Bicarbonate (mg.l-1) Carbonates (mg.l-1) Nitrate (mg.l-1) Phosphorus (µg.l-1) Potassium (mg.l-1) Calcium (mg.l-1) Magnesium (mg.l-1) Sodium (mg.l-1) Sulfate (mg.l-1) Chloride (mg.l-1)

20 Pressure difference (Kg.m -2 ) Pipe pressure test Pressure difference [Entrance Final] irrigation pipes RW RW+CO2 RW+NO3 WW /09/ /11/ /01/ /04/ /06/ /08/ /10/2015 Days 20

21 Water Flow (ml. min -1 ) Water Flow (ml. min -1 ) Evolution of water flow in integral drippers line and emitters 70 Integral dripper line /09/ /04/ /05/ /06/ /07/ /08/ /09/ /10/ RW RW+CO2 RW+NO3 WW PC dripper /09/ /04/ /05/ /06/ /07/ /08/ /09/ /10/ RW RW+CO2 RW+NO3 WW 21

22 Bacterial count (FCU.mm -2 ) Biofilm formation in pipes (sample of 7 May) Reclaimed water 4100 CFU.mL -1 Well water 2320 CFU.mL -1 Reclaimed water CFU.mL -1 Well water CFU.mL -1 1.E+03 May June Compensated dripper Integral dripper 1.E+02 1.E+01 1.E+00 RW RW+CO2 RW+NO3 WW RW RW+CO2 RW+NO3 WW Water treatments 22

23 Visual test Reclaimed water+no 3 Reclaimed water Reclaimed water+co 2 Well water 23

24 Visual test Reclaimed water Reclaimed water+no3 Reclaimed water+co2 Well water 24

25 Preliminary conclusions Thirteen months of treatment, operating in total 90 hours, there has not been enough time to biofilm grow in the pipes and drippers to clogging it. We have not detected an increase of water pressure differences between the in and out of the irrigation pipes. However, in well water emitters there were a small flow increase. The ph of the reclaimed water was increased after three weeks water is maintained in the tank. Perhaps is due to temperature increase because of trees cut clearance around the tank. Then we have to adjust CO 2 injection and nitric acid dosification. Bacterial count in irrigation pipes is very low (1 to 3 logarithm units) and variable.

26 Preliminary conclusions After visual determination of drippers we can see some biofilm but those are not enough to cause of clogging. Irrigation system need to operate more time to have dripper clogging. We will determine the bacterial community composition in order to see if there are differences due to nitric acid or CO 2 treatment. We will continue the measurements of flow pressure, water flow and biofilm formation in different season and air temperatures 26