SUSTAINABLE WASTE WATER

Sustainable Waste Water

Sustainable Waste Water

Introduction

This paper will discuss sustainable wastewater treatment systems including lagoons/wetlands, USAB (anaerobic digesters), Hybrid reactor, and SAT technologies.

Discussion

Lagoons and wetlands

In wetland treatment, natural forces (chemical, physical, and solar) act together to purify the wastewater, thereby achieving wastewater treatment. A series of shallow ponds act as stabilization lagoons, while water hyacinth or duckweed act to accumulate heavy metals, and multiple forms of bacteria, plankton, and algae act to further purify the water. Wetland treatment technology in developing countries offers a comparative advantage over conventional, mechanized treatment systems because the level of self-sufficiency, ecological balance, and economic viability is greater. The system allows for total resource recovery. (van 2006:45)Lagoon systems may be considered a low-cost technology if sufficient, non-arable land is available. However, the availability of land is not generally the case in big cities. The demand of flat land is high for the expanding urban developments and agricultural purposes.

The decision to use wetlands must consider the climate. There are disadvantages to the system that in some locations may make it unsustainable. Some mechanical problems may include clogging with sprinkler and drip irrigation systems, particularly with oxidation pond effluent. Biological growth (slime) in the sprinkler head, emitter orifice, or supply line cause plugging, as do heavy concentrations of algae and (UNEP 2004:45)suspended solids. Other disadvantages are listed in Table below;

Anaerobic Digestion

Another treatment option available, if there is little access to land, is anaerobic digestion. Anaerobic bacteria degrade organic materials in the absence of oxygen and produce methane and carbon dioxide. The methane can be reused as an alternative energy source (biogas). Other benefits include a reduction of total bio-solids volume of up to 50-80% and a final waste sludge that is biologically stable can serve as a rich humus for agriculture. (Schertenlieb 2005:7)

So far, anaerobic treatment has been applied in Colombia, Brazil, and India, replacing the more costly activated sludge processes or diminishing the required pond areas. In various cities in Brazil, they show an interest in applying anaerobic treatment as a decentralized treatment system for “sub-urban”, poor, districts. The beauty of the anaerobic treatment technology is that it can be applied to a very small and very big scale. This makes it a sustainable option for a growing community. (SIDA 2001:01)

There are different types of digesters available, some have been proven effective over time, and others are still being tested. One of the most suitable digesters for tropical conditions is the USAB (upflow anaerobic sludge blanket). In tropical conditions, there are reductions in BOD of 75%-90%. UASB technology is feasible in an urban, developing world context because of its high organic removal efficiency, simplicity, low-cost, low capital and maintenance costs and low land requirements. Typically, USAB's have low sludge production and low energy needs (Rose, 2001). Since nitrogen and phosphorus are not effectively reduced in anaerobic technologies, this primary treatment approach works well with agriculture or aquaculture. However, they are not completely effective at removing all pathogens, the wastewater needs a post treatment ...