Fertigation Efficacy of Municipal Wastewater for Leafy Vegetable Production
Table of Contents
An introduction to the topic “Fertigation Efficacy of Municipal Wastewater for Leafy Vegetables” Fresh water scarcity has attracted farming communities to utilize wastewater for irrigation.
Municipal wastewater (MW) enriched with diverse contaminants including heavy metals is still preferred due to higher concentration of plant nutrients, continuous availability and low cost.
Health Concerns in Wastewater-Irrigated Vegetables
Vegetables irrigated with such water usually contain high contents of heavy metals, which are considered harmful for consumers.
Treated wastewater application for irrigation of vegetables can be an effective strategy to minimize health risks associated with the consumption of contaminated vegetables.
Study Overview and Location
Present study was conducted at Pir Mehr Ali Shah, Arid Agriculture University, Rawalpindi, Pakistan with two cultivars of spinach and lettuce.
Municipal wastewater was collected following standard procedures from Nullah Lei, Gawalmandi, Rawalpindi, Pakistan and it was treated with two types of trickling filters (TFs):
- BT using biological substrates (rice husk, corn cob, and wheat straw)
- PT using physical substrates (sand, medium, fine, and very fine gravel)
Irrigation Treatments
Physico-chemical characteristics of all irrigation treatments and soils were determined with:
- MF, PTF, BTF, TWF, and GF (with NPK supplementation)
- MW, PT, BT, TW, and GW (without NPK supplementation)
Vegetables Tested and Parameters Measured
Leafy vegetables studied were:
- Lettuce: Leaf (L1), Iceberg (L2)
- Spinach: Desi Palak (S1), Lahori Palak (S2)
These were analyzed for:
- Metal accumulation in roots and leaves
- Plant growth/productivity
- Biochemical parameters in all treatments
Physico-Chemical and Metal Content Analysis
Physico-chemical parameters (pH, NO₃⁻-N, COD, PO₄³⁻) and five heavy metals (Ni, Mn, Cu, Co, and Cd) exceeded irrigation standards in MW.
The rest of the six parameters and seven metals were within allowable limits.
Physico-chemical parameters of correspondingly irrigated soils were within safer limits of soil standards except Cu and Cd, which were above safer limits due to wastewater irrigation.
Metal Accumulation in Vegetables
Among studied vegetables, higher metal accumulation was recorded in:
- S1 (Desi Palak): Pb, Co, Zn in roots
- S2 (Lahori Palak): Ni, Cu, Cr in roots under MW and MF treatments
Higher leaf accumulation was found in:
- S1: Pb, Mn, Cr
- S2: Ni, Zn, Fe, Cu, Co, Cd under MW and MF respectively
Bioconcentration and Human Health Risk
Bioconcentration factor (BCF) for all metals was recorded higher in all vegetable roots in MW.
S1 (MW) and S2 (MF) leaves also showed higher BCF in respective treatments.
Significant human health risk is speculated upon ingesting heavy metal-hyperaccumulating S1 and S2 in MW and MF treatments respectively.
Trickling Filter Efficiency
BT treated water showed remarkable reduction in all physico-chemical parameters, particularly heavy metals, compared to PT.
Values of studied parameters in BT closely matched with TW (tap water).
All studied soil parameters in PT, PTF, BT, BTF, TW, and TWF were found within safe limits due to irrigation with treated water.
Biological vs. Physical Filters
Root and leaf metal accumulation remained higher for S1 and S2 in PT and PTF treatments compared to BT, BTF, TWF, and TW, revealing better wastewater treatment efficiency of biological substrate trickling filters.
Similarly, BCF for metals and health risks in adults and children were only found in spinach under PT and PTF treatments.
No health risk was observed in BT and TW treatments.
Crop Safety and Risk Ranking
Lettuce was found to be less of a metal hyperaccumulator compared to spinach.
In this study, fertigative efficacy of municipal wastewater (MW) was recorded — but at the cost of human health risk.
The risk pattern was:
S2 > S1 > L1 > L2
Wastewater Fertigation and Leafy Vegetable Safety Full PDF Copy of the Thesis
Disclaimer
“This abstract is re-organized for readability. For 100% original text, read the full thesis PDF linked above.”
Sources & Thesis Details
Thesis Title: Fertigation Efficacy of Municipal Wastewater for Leafy Vegetables
Researcher: Hina Waheed
Supervisor/Guide: Not listed in abstract
Institution: Pir Mehr Ali Shah Arid Agriculture University, Rawalpindi
Department: Biological & Medical Sciences, Botany
Degree Year: 2019
Publisher: University Research Repository
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