EM 1110-2-501
1 Feb 99
4-1
Chapter 4
Collection Systems
4-1. General
The purpose of a wastewater collection system is to convey wastes from the point of generation to the point
of treatment or disposal. Depending on site conditions and economics, collected wastewater is conveyed
either by truck transport or by piping system. The piping system may employ gravity, pressure, vacuum,
or a combination of the first two. Graywater is defined as all wastewater produced from an occupied
building unit (shower, bath, stationary stands, or lavatories) and generated by water-using fixtures and
appliances, excluding the toilet and possibly garbage disposal, if any. Blackwater refers to pit privy waste
and consists primarily of human excreta.
4-2. Absence of Pressurized Water Supply
When no pressurized water is available or soil conditions are unsuitable for direct ground disposal, the
choice for onsite treatment may be limited to privies or waterless toilets. A privy, an outhouse over an
earthen pit, is the simplest solution. When the pit is full, the privy may be closed or relocated. If the soil
conditions are such that contamination of a groundwater source is a potential problem, impervious pits may
be used and the subsequently collected waste (septage) pumped out and transported to a central holding
tank or station. Both types of privies have been widely used for unserviced campgrounds, parks, and
recreational areas without pressurized water service.
4-3. Transport by Truck
a. General. Trucks are used to transport four types of wastes: septic tank sludge, vault wastes,
recirculating and portable chemical toilet wastes, and low-volume flush wastes. Factors to consider when
designing a truck transport system include length of haul to the treatment facility, frequency of hauls, and
the effect that the trucked waste has on the treatment facility (Clark 1971).
b. Effects on treatment facility.
(1) Table C-10 presents the characteristics of a 3800-L (1000-gal) load of nonwater carriage wastes.
Addition of this wast