Irrigation of food crops with treated wastewater

February 13, 2018 | Author: Anonymous | Category: Math, Statistics And Probability, Normal Distribution
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Case study 3: Irrigation of food crops with treated wastewater Problem Formulation (Background, goal, and breadth) The wastewater treatment plant Harnaschpolder near Delft is one of the largest in Europe. It collects and treats the wastewater of more than 1 million people, treats with conventional biological treatment and discharges 10.000 m³ secondary effluent per hour (dry weather flow). The wastewater effluent could be an alternative source of fresh water for the greenhouse sector – after further treatment. The greenhouse sector does not want to compromise the safety of greenhouse produce for consumers and also for the greenhouse workers. The owners of the wastewater treatment are conducting a research project to look at treatment options. Currently they suggest 2 different treatment lines, 1: use sand filtration and multimedia filtration (for N/P removal) followed by ultrafiltration and reverse osmosis, but this is expensive (different lines shown in Figure 1). Objective:  Assess the risk/probability that lettuce consumers and workers in the greenhouses will get an infection after consuming the lettuce and after exposure to wastewater during irrigation.  Propose the control measures to reduce the risk to consumers and workers and evaluate the effectiveness of these measures. Stakeholders: 1. Wastewater treatment plant operators and administrators 2. Farmers/ workers of green houses 3. Consumers 4. Technology vendors 5. Health authorities 6. National/ international regulatory authorities 7. Residents of the region Figure 1: Treatment lines. LINE 1: Reference treatment (conventional + membranes): no chemical disinfection

WWTP effluent

VIRUS 2-4 Log

VIRUS 1-2 Log

Microbiological barriers

SAND FILTRATION

MULTIMEDIA FILTER

100um-10um

100um-1um

NO3-

PO4- & Susp. solids

UF

RO

100-10nm

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