Alternative Kinds of Sewage Systems

Alternative sewage systems are generally designed for pollution-sensitive areas where conventional systems are unsuitable. This includes wetlands or near rivers and lakes, where soil permeability is poor or groundwater levels are high. Alternative systems either modify or completely replace traditional treatment systems. Most are more costly to install and maintain but are more efficient at treating sewage. Several alternative methods are available, and almost all require a continuous electrical supply.

Pumping Chambers

• Pumping chambers are present in nearly all alternative systems. A pumping chamber contains an electric pump in an impermeable container, which also stores effluent or wastewater to be pumped into the treatment system. The electric pump is programmed to run according to the schedule of the operator. The size and per-hour capacity of pumps determine the amount of effluent applied during each cycle. Most pump chambers are fitted with float systems that switch the pump off when effluent reaches above or below critical levels.

Primary Treatment

• Effluent in alternative systems undergoes primary treatment in a similar manner and purpose to conventional systems. Both systems use a septic tank fitted with an outlet filter to prevent tiny solid pollutants from entering the secondary treatment phase. In alternative systems however, the effluent is more thoroughly treated before leaving the septic tank.

Secondary Treatment

• Secondary treatment is important in alternative systems. There are several different techniques applied to this stage of treatment, which are categorized into fixed-media and suspended-growth systems. In fixed media systems, primary effluent is transported over a permeable media containing aerobic bacteria and exposed to atmospheric oxygen in an impermeable chamber. Effluent filtered through the media is then collected. Suspended-growth systems undergo a similar process, but the effluent and atmospheric oxygen is rapidly circulated by mechanical agitation.

Disinfection

• Disinfection is applied to effluent treated for recycling and irrigation. This eliminates the threat of pathogenic microorganisms. Organic pollutants must be removed during secondary treatment as they disrupt the disinfection process. Disinfection techniques include chlorination, ultraviolet light and ozonation. Chlorination involves the simple addition of chlorine to the effluent. Ozone gas is injected into effluent during ozonation and utilizes complex equipment. Ultraviolet disinfection is technically simpler than chlorination and ozonation but more expensive as ultraviolet bulbs need regular replacement.