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Water has always been an important and life-sustaining drink to humans and is essential to the survival of all known organisms. Over large parts of the world, humans have inadequate access to drinking water and use water contaminated with disease vectors, pathogens or unacceptable levels of toxins or suspended solids. Drinking such water or using it in food preparation leads to widespread, acute and chronic illnesses and is a major cause of death and misery in many countries. The UN estimates that over 2.0 billion people have limited access to safe water and nearly 800 million people lack even the most basic supply of clean water. The main issue is the affordability of water purifying systems. Many people rely on boiling water or bottled water, which can be expensive. Therefore, technologies that are cost effective, sustainable, ease of operation/maintenance and the treatment processes with locally available materials are required. In this article, some unique low-cost sustainable technologies available/or in-use, i.e. natural filtration, riverbank filtration, biosand filtration, membrane filtration, solar water disinfection technique, biologically degradable materials such as moringa powder, scallop powder treatment, and biosand pitcher treatments have been discussed.

Background: Cow milk is considered as one of the responsible food sources contaminated with heavy metals. The objectives of the study were to assess the content of selected metals in cow milk and its associated human health risks in the food chain of Bangladesh. A total of 90 cow milk samples of Branded, Dairy and Domestically produced milk were collected randomly from different sources of Savar Upazila in Dhaka area. Cadmium (Cd), chromium (Cr), lead (Pb), manganese (Mn), copper (Cu) and iron (Fe) contents in collected milk samples were determined using Flame Atomic Absorption Spectrometry (FAAS). To ensure quality control, one of the best quality control parameters i.e. recovery test; from eight various sample digestion methods were used. The Hazard Quotient (HQ) and Carcinogenic Risk (CR) values were also calculated. Results: From the results, it was found that, the orders of heavy metal content in brand, dairy and domestic cow milk were Cr > Fe > Cu>Mn > Cd > Pb, Cr > Fe > Mn > Cu > Cd > Pb and Fe > Cr > Mn > Cu > Cd > Pb, respectively. Among the six metals, only Cr showed to exceed the highest Estimated Daily Intake (EDI) rate (for brand cow milk: 0.413 mg/day, dairy farm cow milk: 0.243 mg/day, domestic cow milk: 0. 352 mg/day),and the comparison percentages of calculated values per permeable values were as follows; 206.5 % for brand cow milk,121.5 % for dairy farm cow milk and 176.0 % for domestic cow milk. Hazard Quotients (HQ) values and Carcinogenic Risk (CR) values were found within the acceptable level. Conclusion: Although, the metal content in sampled cow milks were within the safe limit, the potential human health risks cannot be neglected for the regular/long time consumption of heavy metal contained cow milk.