Tehran, the capital of the Islamic Republic of Iran, is a case of unplanned urban development. About 12% of Iranians are Tehran dwellers, and geology plays a major role in their environment. The city is located in northern Iran in the foothills of the Alborz Mountains. Sediments underlying the city are composed of coarse (northern part of Tehran) to very fine (southern part of Tehran) sandstone, siltstone, and mudstone with interbeds of gravels and pebbles in various proportions up to a depth of 1600 m. The early settlers were attracted to the area because there were bountiful springs and kanats (or qanats, an underground channel with vertical access shafts used to transport water from an aquifer under a hill to the surface without the need for pumping). The inharmonious geomorphology has strongly influenced the local climate for Tehran, with northern portions of the city in the humid mountains and southern portions in the desert. As development and expansion of the urban area continue, there will be increasing demand for natural resources and services such as water supply and construction material, land-use changes, increasing pollution, and exposure to geological hazards. In this article, we use surface and subsurface geological data to highlight the geological constraints on sustainable urban growth and management.

Earth systems, when understood and respected, have the intrinsic capability to be instrumental for sustainable international development. If applied wisely without sophisticated technology, natural processes themselves can serve to sustain and prosper life in specific situations. Global initiatives to provide safe surface and groundwater are booming, but a parallel emphasis on sustainable sanitation is lagging, leaving 2.5 billion people without access to improved sanitation. Many technically sophisticated sanitation systems exist but are beyond the means of those same billions. The Water and Sewage Transformation Endeavor (W.A.S.T.E.) is a program at Wheaton College (Wheaton, Illinois) bringing together undergraduate students and faculty from various natural and social sciences to address the global need for improved sanitation. The goal of the program is to develop a low-tech wastewater treatment system for the Global South and beyond. A laboratory-scale waste stabilization pond system was constructed and studied to compare its effectiveness at reducing biological oxygen demand (BOD), as an indicator of pathogen disinfection, by varying light intensity, temperature, and detention time. The system with the highest light intensity and temperature and longest detention time performed the best, achieving 95% total BOD reduction. The project time line includes phase 1 indoor experimentation, phase 2 installation and operation of an outdoor pilot system, and the final phase 3 development of training programs for deployment of the technology into areas of need. The overall program has already proven to be an excellent educational opportunity for undergraduate students. It will ideally benefit many other student practitioners, and local trainees at candidate sites.