Considerable investments have been made in establishing wastewater treatment plants (WWTPs). However, evaluation of the performance of plants during recent years, when more WWTPs have become operational, shows that effluent quality criteria were not met in many instances. Preliminary assessment of the operational problems of WWTPs in Iran disclosed that numerous factors affect this issue of eff...

Soils of the tropics and sub-tropics are typically acid and depleted of soluble sources of silicon (Si) due to weathering and leaching associated with high rainfall and temperatures. Together with intensive cropping, this leads to marginal or deficient plant Si levels in Si-accumulating crops such as rice and sugarcane. Although such deficiencies can be corrected with exogenous application of S...