Organic Waste Recycling

Land treatment of wastewater 411

W = Lh + 50 (humid)
W = Lh - 50 (arid)
The amount of percolating water, W, resulting from the applied wastewater,
Lh, has a significant effect on the allowable nitrogen loading, L'n.
From Equation 8.4, the annual N balance is:

L'n = U + D + 0.1 W Cn

for humid L'n = 336 + .2 L'n + (0.1)(Lh + 50) 10

for arid L'n = 336 + .2 L'n + (0.1)(Lh - 50) 10

The relationship between the nitrogen loading and the hydraulic loading is :
L'n = 0.1 C'n Lh (SI units). Where, L'n = wastewater nitrogen loading, kg/(ha-yr);
C'n = applied nitrogen concentration, mg/L; Lh = wastewater hydraulic loading,
cm/yr.

L'n = 0.1 x 25 Lh = 2.5 Lh

or Lh = 0.4 L'n

For humid climate,

L'n = 336 + .2 L'n + 0.1(0.4L'n + 50)x10

= 965 kg/(ha-yr)

Lh = 965 x 0.4 = 386 cm/yr

For arid climate,

L'n = 336 + .2L'n + 0.1(0.4L'n - 50)x10

= 715 kg/(ha-yr)

Lh = 715 x 0.4 = 286 cm/yr

Summary of solutions

Humid Arid

1. Wastewater N loading, (L'n), kg/(ha-yr) 965 715


2. Wastewater hydraulic loading, (Lh), cm/yr 386 286


3. Percolating water, (W), cm/yr 436 236


4. De-nitrification, (D), kg/(ha-yr) 193 143


5. Percolate N loading (P'n), kg/(ha-yr) 436 236
   (P'n = 0.1 Cn W = L'n - U - D)