Alternative low-cost adsorbent for water and wastewater decontamination derived from eggshellwaste: an overview

As the current global trend towards more stringent environmental standards, technical applicability and cost-effectiveness became key factors in the selection of adsorbents for water and wastewater treatment. Recently, various low-cost adsorbents derived from agricultural waste, industrial by-products or natural materials, have been intensively investigated. In this respect, the eggshells from egg-breaking operations constitute significant waste disposal problems for the food industry, so the development of value-added by-products from this waste is to be welcomed. The egg processing industry is very competitive, with low profit margins due to global competition and cheap imports. Additionally, the costs associated with the egg shell disposal (mainly on landfill sites) are significant, and expected to continue increasing as landfill taxes increase. The aim of the present review is to provide an overview on the development of low-cost adsorbents derived from eggshell by-products

Wastewater treatment in an integrated laboratory system

Integrated laboratory system consisted of three stages - activated sludge reactor, biofilter and subsurface vertical flow wetland was used to treat two types of wastewaters differed in their generation and pollution. Wastewaters from a pig farm as well as from a landfill site for domestic wastes were used in the experiments. The BOD/COD ratio of the wastewaters from a pig farm and from the landfill leachate was 0.5 and 0.07, respectively. In the first stage of the integrated system was achieved COD removal (48 % for the piggery wastewater for 3 days and 62.3 % for the landfill leachate after 4 days). BOD removal (55.6 %) for the piggery wastewater was achieved in 3 days and 24.9 % - for the landfill leachate after 4 days. The decreasing of organics at aerobic conditions was accompanied with the ammonium ions decreasing - 1.5 times for the piggery wastewater and 4 times for the leachate. In the second stage - biofilter without aeration, an additional organic loading decreasing was achieved. The COD decreased from 820.9 mg/dm3 to 274.3 mg/dm3 for piggery wastewater and for the leachate - from 869.5 mg/dm3 to 423.6 mg/dm3. The BOD values decreased from 384.1 mg/dm3 to 106.8 mg/dm3 for the piggery wastewater and for leachate - from 117.8 mg/dm3 to 57.4 mg/dm3. The ammonium ions were eliminated from both types of wastewaters. In the third stage (subsurface vertical flow wetland) the emission standards for discharge into the sewage collection systems or into the water bodies are met