Role of pipe material and organic suspended solids on biofilms, emitter performance, and plant growth
Description
This dataset supports a study investigating how pipe material and organic suspended solids (TSS) influence biofilm formation, microbial community composition, and emitter performance in greenhouse drip irrigation systems equipped with anti-drain mechanisms. The research hypothesis posited that pipe material and organic load would significantly affect biofilm development and microbial diversity, thereby impacting irrigation uniformity and emitter function. The experiment used polyvinyl chloride (PVC) and polyethylene (PE) pipes with nutrient solutions containing 0, 30, 60, and 120 mg/L of peat-derived suspended solids (<150 µm). Systems operated twice daily for eight weeks across two independent runs. Biofilm accumulation was quantified via dry mass and heterotrophic plate counts (HPC), while microbial communities were characterized using 16S rRNA and ITS2 amplicon sequencing. Pipe surface properties were assessed for hydrophobicity and roughness before and after biofilm exposure. Key findings include: PVC pipes accumulated more biofilm than PE pipes, with significant changes in surface hydrophobicity and roughness post-exposure. Pipe material had a stronger influence on microbial community structure than organic load, with distinct bacterial and fungal profiles observed between PVC and PE. Organic TSS concentrations ≥60 mg/L increased emitter discharge, leading to reduced irrigation uniformity, though no emitters were fully clogged. Biofilms in PVC pipes did not affect downstream PE pipes, suggesting limited microbial transfer between materials. Microbial taxa capable of polymer degradation and EPS production were prevalent, indicating potential feedback mechanisms where biofilms alter pipe surfaces to promote further colonization. Data interpretation suggests that pipe material selection is critical for managing biofilm-related clogging risks. PE pipes may offer advantages in biofilm resistance and ease of replacement. Additionally, maintaining organic TSS below 60 mg/L is recommended to prevent overirrigation and associated agronomic and economic impacts. The dataset includes emitter performance metrics, biofilm biomass, microbial OTU tables, and pipe surface characterization. Sequencing data are available in the NCBI SRA (PRJNA1355485).
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This study evaluated the effects of pipe material and organic suspended solids (TSS) on biofilm formation and emitter performance in greenhouse drip irrigation systems. The experiment was conducted in two independent 8-week runs using a controlled irrigation setup that mimicked commercial greenhouse conditions. System Setup and Treatments A proportional dosing pump (Dosatron D14MZ2) injected a 15-2.2-12.5 Ca–Mg fertilizer solution at 150 mg/L nitrogen into PVC main lines. Organic TSS treatments (0, 30, 60, 120 mg/L) were introduced using electromagnetic diaphragm dosing pumps (Etatron DLXB). Peat moss was dried (65°C, 72 h), ground (UDY cyclone mill, 0.5 mm screen), and sieved (<150 µm) using a Ro-Tap shaker. Each main loop consisted of six 2.1 m PVC pipes (Schedule 40, 20 mm I.D.) connected with elbows and threaded fittings for biofilm sampling. These fed two 2.1 m PE lateral lines (16 mm I.D.) with six pressure-compensating anti-drain drippers (2 L/h nominal discharge). Irrigation occurred twice daily for two minutes at 0.2 MPa pressure. Emitter Performance Measurement Baseline emitter flow rates were measured using graduated cylinders. Weekly measurements were used to calculate: Christiansen Uniformity Coefficient (CU): CU = 100 × (1 − CV) Discharge Variation Ratio (Dra): Dra = 100 × Σ(q_im / q_in) / n Where q_im is measured flow rate, q_in is initial flow rate, and n is the number of emitters. Biofilm Sampling and Analysis At the end of each run, biofilm accumulation was quantified using: Dry Mass: Pipe sections dried at 95°C, weighed before and after cleaning, normalized to surface area. Heterotrophic Plate Counts (HPC): Biofilm scraped into PBS, serially diluted, plated on 3M™ Petrifilm™, incubated 48 h. Microbial Community Composition: DNA extracted using DNeasy PowerWater kit, filtered through 0.22 µm PES membranes. Sequencing was performed at the University of Connecticut’s MARS facility using Illumina MiSeq (2×250 bp) targeting 16S rRNA (V4) and ITS2 regions. PCR used Accuprime PFX mix with BSA, and primers with dual indexing (515F/806R for bacteria, ITS3/ITS4 for fungi). Data were processed in Mothur v1.39.4 following MiSeq SOP, aligned to SILVA nr_v119, and classified using RDP Bayesian classifier. Pipe Surface Characterization New and biofilm-exposed PVC and PE pipes were analyzed at the Institute of Materials Science (UConn) for: Hydrophobicity: Sessile drop method (ASTM D7334–08) using OCA–20 tensiometer. Surface Roughness and Waviness: Zygo NewView 5000 interferometer, analyzed per ISO 25178–604 and ISO 13565–1. Experimental Design and Analysis Main experiment: 2 (pipe materials) × 4 (TSS levels) factorial RCBD with 5 blocks and 20 units. Surface study: 2 (biofilm age) × 3 (pipe sets) factorial CRD. Statistical analysis used SAS® 9.4 (PROC MIXED, REG), with Tukey’s HSD for mean separation (_P_≤0.05). Data transformations ensured parametric assumptions.
Institutions
- University of Connecticut