Abstract

The discharge of chromium into the environment has become a problem of great concern all over the world including Pakistan for a few decades. The present research was conducted to study the bioremediation effect of carbon-activated granules (CAAGs) of two algal strains as a novel biosorbent for chromium from tannery effluent in addition to improvement of different water quality indicators. Effect of sorbent dose (5, 7 and 9 g L⁻¹) and contact time (0–140 h with interval of 20 h) on chromium removal was evaluated. Maximum chromium removal (9.33 mg L⁻¹ and 7.60 mg L⁻¹) from raw tannery wastewater (WW) was reached after 120 h using 9 gL⁻¹ of Chlorella vulgaris and Scenedesmus obliquus biomass, respectively. Rate of Cr removal was found directly proportional with dose of granulated algae and incubation period. Carbon-activated granules of Chlorella vulgaris as a biosorbent (9 g L⁻¹⁾ exhibited 19.47% more chromium removal in 10 times diluted WW compared to raw WW. The CAAG of both isolates reduced COD (38.08% and 34.72%), BOD (37.04% and 13.60%) and TSS (34.01% and 36.30%) for Chlorella vulgaris and Scenedesmus obliquus, respectively. Meanwhile, both CAAG types decreased TSS by around 85% while resulting in a slide increase in pH compared to initials. The CAAG of both isolates proved to be promising candidates for environmental bioremediation by reducing chemical and biological oxygen demand and total suspended solids of tannery WW by developing cost-effective and ecofriendly process in the prevalence of sunlight.

Graphic abstract

中文翻译：

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使用小球藻和斜生藻的碳激活藻类颗粒对皮革厂废水中的铬进行生物吸附

摘要

将铬排放到环境中已经成为包括巴基斯坦在内的世界各地极为关注的问题。本研究旨在研究两种藻类的碳活化颗粒（CAAG）的生物修复效果，作为制革厂废水中铬的新型生物吸附剂，此外还改善了不同的水质指标。评估了吸附剂量（5、7和9 g L ^-1）和接触时间（0-140小时，间隔20小时）对铬去除的影响。使用9 gL ^-1的小球藻和斜生小球藻120小时后，从制革厂废水（WW）中最大去除铬（9.33 mg L ^-1和7.60 mg L ^-1）。生物质。发现Cr去除率与粒状藻的剂量和潜伏期成正比。与原始WW相比，在10倍稀释的WW中，作为生物吸附剂的小球藻的碳活化颗粒（9 g L ^-1）去除的铬增加了19.47％。两种分离物的CAAG均降低了小球藻和斜生场面藻的COD（38.08％和34.72％），BOD（37.04％和13.60％）和TSS（34.01％和36.30％）。， 分别。同时，两种CAAG类型均使TSS降低了约85％，同时导致pH值与初始值相比有所增加。通过在日光照射下开发具有成本效益且环保的工艺，通过降低化学和生物需氧量以及制革厂WW的总悬浮固体，这两种分离株的CAAG被证明是有希望的环境生物修复候选物。

图形摘要