farham karakani

Selection of different wastewater treatment methods depends on the kind of wastewater, geographical position of the community, quantity and quality of wastewater and effluent, technology and finance. Natural wastewater treatment methods are simple, cheap and acceptable for developing countries specially small and remote countries and wetland is one of these methods. Wetlands include two categories: natural and constructed. Moreover, constructed wetlands are of two types of sub-surface flow and free water surface. The aim of this paper is to investigate wetland usage backgrounds and history of application in Iran and other countries.

This is a review of the practical work and comparison of constructed subsurface flow wetland system's efficiency in wastewater treatment in Iran and foreign countries.

In many countries average of removal efficiency by wetland for BOD, TSS, TP and TN was about 91.6%, 81.6%, 78.8% and 70.8% respectively, and for Iran they were 77%, 83%, 78%, and 83%, respectively.

The results of the current research showed that in foreign countries wetland systems are used for all kinds of wastewater and have good removal efficiency, unfortunately in Iran wetland is not widly used and it has only been used in a few domestic cases.

Various chemicals are used to produce polymers, leakage of polymer materials over the time, can cause health problems The aim of this research was to evaluate the leakage of heavy metals from the PVC and polypropylene pipes used in the water distribution system in Isfahan.

Four brands of PP pipes and two various types of PVC pipes were analyzed in this study.Concentration and leakage of heavy metals (lead, cadmium, nickel, chromium, zinc and tin) at 20 ° C were measured and compared with national standards of Iran, US Environmental Protection Agency (EPA) and the World Health Organization (WHO) guidelines.

Mean lead concentration in used and new PVC pipes was higher than other pipes and there was significant difference between these two PVC pipes and other pipes in lead concentration. Mean leakage of lead was higher in PP pipes produced in A and B manufacturing plants. Lead leakage was lower than Iranian standards, but exceeds than EPA standards and WHO guidelines in PP pipes produced in A and B manufacturing plants. Cadmium leakage from PP pipes produced in C manufacturing plant exceeds all standards and guidelines.

Inappropriate plastic production process increases the possibility of stabilizers and plasticizers releasing. Regarding direct relation between use of polymer pipes and consumer’s health, control of pipes producer by related institutions is proposed in accordance with make changes in stabilizers and preventing application of heavy metal-based pigments to overcome the mentioned problems.