Artisanal tannery wastewater: quantity and characteristics

Abstract

Tannery wastewater is one of the most toxic waste generated in industries. In spite of this, there still remains a paucity of information on characteristics of wastewater generated from artisanal tanneries. This study, therefore, assessed the water consumption, wastewater generation rates, physicochemical and microbiological characteristics of wastewater produced from each process unit of an artisanal tannery in Ghana. The study revealed that the total amount of water use in the tannery ranged between 1171 and 2120L/day whilst the total volume of wastewater generated was within 820 and 1324L/day. Physicochemical characteristics of the different wastewater types generated at the tannery including chemical oxygen demand (13600–24333.30 mg/L), biochemical oxygen demand (1445.64–2803 mg/L), ammonia (3.20–21.38 mg/L), colour (950.35–53900.10PtCo), electrical conductivity (8170 - 10080 μS/cm), turbidity (450.24–1805NTU), suspended (1033.50–3216.40 mg/L) and dissolved (26166.50–4996.65 mg/L) solids exceeded the guidelines set by the Ghana Environmental Protection Agency. There were also high levels of chlorides, sodium, sulphates and calcium ions. The most dominant anion and cation in the wastewater were chlorides (715–20490.60 mg/L) and sodium ions (258–14056.45 mg/L) respectively. Heavy metals identified in the wastewater included zinc, aluminium, iron and chromium ions with the most dominant one being aluminium ions (0.58–78.18 mg/L). Whilst the E-coli was below detectable limit, the count of total coliforms ranged between 0 and 4.5 × 10 4 CFU/100mL. Five helminth egg species ( Ascaris lumbricoides, hookworm , Trichuris trichiura , Strongyloides stercoralis, and Enterobius vermicularis ) were identified with their numbers surpassing the safe limit set by the World Health Organisation for irrigation purposes. These results indicated that the indiscriminate discharge of the untreated wastewater on the bare soil as it is practised at the tannery has the potential to adversely affect public and environmental health. Appropriate treatment schemes are therefore, required to treat the wastewater to safe limits prior to discharge.

Performance Optimization of Chemical and Green Coagulants in Tannery Wastewater Treatment: A Response Surface Methodology Approach

“…Te wastewater is dark-red in colour (22400 Pt-Co) resulting from the tannins and dyes applied in the leather production process [32]. Its total dissolved solid (4585.25 mg/L) and suspended solid (3441.25 mg/L) contents as well as its high turbidity (1380 NTU) levels originating from the plant materials used in the leather making process [33] also surpassed the Ghana EPA set limits of 1000 mg/L, 50 mg/L, and 75 NTU, respectively. Te average COD (9459.34 mg/L) and BOD 5 (2639 mg/L) concentrations of the tannery wastewater exceeded the permissible limits of 250 mg/L and 50 mg/L, respectively, by nearly 38 and 21 times, respectively.…”

Characterization and Impact of Physicochemical Parameters of Tannery Effluent on the Aquatic Environment

“…Calcium, sodium, potassium, and sulphate: Using a flame photometer (Model Chemito-1000) and the Jackson method, the calcium, sodium, potassium, and sulphate of the samples were determined 15 . Chloride and chromium: The chloride and chromium contents of the effluent were estimated by argentometric method 14,16,17 .…”

Bone Char Adsorption of COD and Colour from Tannery Wastewater: Breakthrough Curve Analysis and Fixed Bed Dynamic Modelling

“…The equilibrium adsorption capacity, q e for COD (mg/g) or colour (Pt-Co/g), was calculated based on Equation (5).…”

“…The utilisation of diverse chemicals, including dyes, chromium salt, aldehydes, vegetable tannins, bactericides, sodium chloride, surfactants, sodium sulphide, sulphonated oils, lime, ammonium sulphate, sulphuric, and formic acids [2,3] coupled with hair, blood, and flesh, which exude from the animal skins or hides results in very highly complex and toxic wastewater [4]. Not only is this wastewater strongly odourous, saline, and coloured, but it is also heavily laden with suspended matter, nitrogenous substances, and recalcitrant organic matter, which is usually measured as chemical oxygen demand (COD) [5]. Worrisomely, this noxious wastewater is often indiscriminately discharged into rivers and lakes, particularly in low-income countries, including Bangladesh [6], Nigeria [7], Ethiopia [8], Ghana [9], and Pakistan [10].…”