358 Organic waste recycling: technology and management
Based on the data shown in Figure 7.17, the values of k as a function of q are
given in Table 7.8.
Climatic influences
Surface area loading rates are much lower in aquatic systems than conventional
systems, typically more than two orders of magnitude lower. A consequence of
these lower loading rates is greater exposure to climatic factors such as
temperature, rain, and wind. Any of these factors can disrupt treatment by altering
the aquatic environment or damaging the plants. In general, the use of aquatic
plants native to the climatic regime at the aquatic system site is encouraged but, in
certain cases, this may not be desirable or possible.
Figure 7.16 NH 4 +- N removal as a function of hydraulic application rate
(corresponding loading rates for NH 4 +- N are as shown) (after Weber and
Tchobanoglous 1985; reproduced by permission of the Water Pollution Control
Federation, USA)
Temperature
Wastewater in aquatic systems will be warm in summer and cool in winter
because of the large surface areas and long hydraulic residence times. A 10°C
rise or drop in temperature is generally known to double or halve the metabolic
Removal rate, kg NH+-N / (ha-day) 4Hydraulic application rate, m^3 / (m^2 -day)126 kg NH 4 +-N / (ha-day)121 kg NH 4 +-N / (ha-day)131 kg NH 4 + -N / (ha-day)