🏛️ 1. Production Facility & Irrigation Setup

Crop Species Preset (TUR Profiles)

Cultivation Area (m²)

Daily Irrigation Dose (L/m²·day)

Drainage Fraction (DF %)

Recirculation Reuse Ratio (%)

💧 2. Fresh Makeup Water Baseline (Raw Water Quality)

Raw Water Source Presets

Raw Water EC (dS/m)

Raw Sodium Na⁺ (mmol/L)

Raw Chloride Cl⁻ (mmol/L)

Raw Calcium Ca²⁺ (mmol/L)

Raw Sulfate SO₄²⁻ (mmol/L)

Target Feeding EC (dS/m)

📈 3. Dynamic Multi-Cycle Ion Accumulation (1~30 Cycles)

✅ Safe Recirculation Loop

Tracking the mathematical mass-balance trajectory of non-absorbed sodium (Na⁺), chloride (Cl⁻), and electrical conductivity drift over repeated recirculation cycles.

― Na⁺ Sodium (mmol/L) ― Cl⁻ Chloride (mmol/L) ― Total Solution EC (dS/m) --- Crop Threshold Limit

No purge required in 30 cycles

🧪 4. Davies Equation Activity Coefficient Solver

Thermodynamic correction for non-ideal electrolyte interactions in concentrated nutrient solutions: log₁₀(γᵢ) = -0.509·zᵢ²·[√I/(1+√I) - 0.3·I], where chemical activity aᵢ = γᵢ·cᵢ.

Ion Species	Valence (z)	Nominal (mmol/L)	Ionic Str (Iᵢ)	Activity Coeff (γ)	Effective Activity (aᵢ)	Transpiration Uptake (TUR)

📊 Simulation Summary

Purge Trigger

30+

Cycles (Days: 75d)

Water Savings

85.0%

13,961 m³/year

Fertilizer Saved

28.4%

4,820 kg NPK/yr

Financial Gain

$24.2k

€22,500 / ₩33M yr

Daily Irrigation Volume: 45,000 L/day

Recycled Drainage Volume: 11,475 L/day

Ionic Strength (I): 0.0382 mol/L

Mean Monovalent γ₁: 0.865

🇩🇪 DüV Compliance & ESG Dossier

CERTIFIED ZERO-DISCHARGE

German DüV (Düngeverordnung) & EU Water Framework Directive (2000/60/EC) Compliance: Closed-loop recirculating systems prevent agricultural nitrate (NO₃⁻) and phosphate (H₂PO₄⁻) runoff into municipal watersheds.

• Groundwater Leaching Avoidance: 100% Zero Runoff

• Total Annual Nitrogen Conserved: 1,420 kg N

• Total Annual Phosphate Conserved: 380 kg P₂O₅

💡 Agronomist Steering Notes

1. Sodium Flush Threshold: Once rootzone Na⁺ exceeds crop threshold (8.0 mmol/L), plant roots suffer competitive inhibition of K⁺ and Ca²⁺ uptake, risking tipburn and blossom-end rot (BER).

2. Makeup Blending Rule: Maintain a minimum 15% fresh water dilution to buffer against sudden ionic spikes during peak mid-day solar transpiration.

3. UV-C & Ozone Sanitation: Recirculated drain water must undergo 254nm UV-C irradiation (250 mJ/cm²) to eliminate Pythium and Fusarium zoospores prior to A/B tank reinjection.

📚 Chemical Speciation & German DüV Regulatory Framework

In closed-loop hydroponic fertigation, individual nutrient ions do not behave as ideal solutes. Electrostatic interactions reduce the effective thermodynamic concentration (chemical activity $a_i = \gamma_i \cdot c_i$). The Davies equation computes single-ion activity coefficients ($\gamma_i$) up to ionic strengths of $I = 0.1\text{ mol/L}$, preventing false oversaturation predictions of calcium sulfate ($\text{CaSO}_4$) and calcium phosphate ($\text{CaHPO}_4$).

Under the German Fertilizer Ordinance (Düngeverordnung - DüV) and EU Water Framework Directive (WFD), discharging nitrate- and phosphate-rich leachate into surface water or shallow groundwater is strictly prohibited. Operating a closed recirculation loop with automated partial purge triggers ensures 100% regulatory compliance while reclaiming $85\text{--}92\%$ of drained macronutrients.

❓ Recirculation FAQ

Q: How do you prevent sodium accumulation in rain-fed vs municipal water systems?

Rainwater harvested from greenhouse roofs contains virtually zero sodium ($< 0.1\text{ mmol/L}$), permitting $25\text{--}40$ complete recirculation cycles before purging. Groundwater containing $> 1.5\text{ mmol/L Na}^+$ requires reverse osmosis (RO) desalination before entering the recirculation reservoir.

Q: What is Transpiration-to-Uptake Ratio (TUR)?

TUR defines the molar ratio of nutrient ion uptake per liter of water transpired by the crop ($\text{mmol ion / L } \text{H}_2\text{O}$). When an ion's supply concentration exceeds its TUR, that ion inevitably accumulates in the slab, elevating rootzone osmotic pressure.