Organic Waste Recycling

70 Organic waste recycling: technology and management

viruses can be found in Standard Methods (APHA, AWWA, WEF 2005). The
detection of helminth ova can be conducted according to the procedures outlined in
Mara and Cairncross (1989).

Table 2.26 Relative health risks from use of untreated excreta and wastewater in
agriculture and aquaculture (IRCWD 1985)

Class of pathogen Relative excess frequency of infection

or disease

1. Intestinal nematodes: Ascaris, Trichuris,
   Ancylostoma, Necator

High

2. Bacterial infections: bacterial diarrheas
   (e.g. cholera), typhoid.

Lower

3. Viral infections: Viral diarrheas,
   hepatitis A

Least

4. Trematode and cestode schistosomiasis,
   clonorchiasis, taeniasis

From high to nil, depending upon the

particular excreta use practice and local

circumstances

In the design and operation of a waste treatment/recycling system, the
engineer/scientist in charge has to ensure that the public health risks are kept to a
minimum. Each country or state/province normally develops its own standards of
microbiological quality to be used in the disposal or reuses of wastewater and
sludge.
A report published by the International Reference Centre for Wastes Disposal
(IRCWD 1985) proposed the relative health risks from the use of human excreta
and wastewater as shown in Table 2.26. The microbiological quality guidelines for
wastewater reuse in agricultural irrigation are recommended as given in Table 2.27,
while those for aquacultural use of wastewater and excreta are given in Table 2.28.
Because of their relatively high health risks, almost complete removal of the ova of
intestinal nematodes is emphasized. The guidelines for restricted irrigation aim to
protect the health of agricultural workers who are at high risks from nematode
infection, while those for unrestricted irrigation are to protect the health of the
consumers of the crops. Fecal coliform concentrations of 1000 and 10000
(geometric mean) no. per 100 mL or less are recommended for wastewater to be
used in unrestricted irrigation and aquaculture respectively. Because of the high
risks of helminthic disease transmission through aquacultural practices, all
helminth eggs present in the organic wastes must be rendered non-viable or
removed prior to reuses. In areas where there is a high prevalence or an outbreak of
a particular disease, attention should be given to the detection of the infectious
agent present in the waste to be recycled, or the waste recycling practice is
terminated until the disease is under control.