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A B S T R A C TEvery year increasing amounts of industrial waste are generated worldwide. Depending on their characteristics, wastes can represent an important source of secondary raw materials in order to replace natural resources. The growing amount of carbide lime waste (CLW), a byproduct of acetylene production, has resulted in environmental problems. In the present study, the potential use of CLW for wastewater treatment was investigated. The main characteristics of the CLW were determined. Chemical and X-ray diffraction analyses indicated that CLW was similar in chemical and mineralogical compositions to industrial lime, except for the presence of carbon in the waste. Morphological and elemental chemical analyses by scanning electron microscopy and energy dispersive X-ray spectrometry revealed that CLW particles differ from industrial lime by the presence of carbon formations. The use of CLW was evaluated in the treatment of Annaba city wastewater effluent. CLW was found to be the suitable for the treatment of Annaba city wastewater for an optimal dose of 850 mg L À1 . Percentage removal efficiency for turbidity, total suspended solids (TSS), chemical oxygen demand (COD) and 5-day biochemical oxygen demand (BOD 5 ) was found to be 96, 98.2, 90 and 84.5%, respectively. Residual turbidity in supernatant was 4.5 NTU and total residual bacteria was 68 CFU mL À1 . Algerian effluent quality standards for TSS and COD were met after treatment. However, BOD 5 , bacterial level and pH were high, emphasizing the need of pH adjustment and secondary treatment for the Annaba city effluent. The precipitation of heavy metals with CLW has been shown to be successful in reducing the level of soluble heavy metals in aqueous solution. The removal of heavy metals was enhanced at pH ranges 10À11 for zinc, 9.2À11.6 for lead, 4À11.8 for iron and 7À11.8 for copper. The results revealed that CLW can be effectively used in wastewater treatment.

In this study, the dromedary bone waste was valorized by the obtainment of hydroxyapatite (HAp) and its application to remove crystal violet (CV) dye from aqueous solution. Fourier transform infrared spectroscopy, X‐ray diffraction, elemental analysis X‐ray fluorescence spectrometer (XRF), particle size laser analysis, and the point of zero charge pH value (pHpzc) were realized to characterize the natural adsorbent. The capacity of HAp to adsorb CV was measured at different contact times, pH values, and initial dye concentrations. The results showed that the model that better described the experimental data of adsorption kinetics was the pseudo‐second‐order kinetic model (PSO). Freundlich model well fitted the sorption isotherms. A maximum sorption capacity of 266.66 mg/g of CV dye on natural HAp was obtained. Hence, dromedary bone treated might be valorized as a natural adsorbent for water treatment with low environmental risks.

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a b s t r a c tThe objective of this work is to promote carbide lime waste (CLW), rejected in nature to reduce the pathogens in urban wastewater sludge. We have engaged in this research project, which is notably based on an integrative approach to CLW in urban sludge stabilization. Due to their intrinsic physical and chemical properties, CLW showed excellent and attractive results for urban wastewater sludge stabilization of Bordj Bou Arreridj city. The obtained results show that the stabilization of sludge is most efficient with high level of CLW percentage. The best elimination of pathogenic microorganisms and dryness is obtained for a 50% CLW dose for various microorganisms such as fecal D Streptococcus, fecal coliform, total mesophilic flora and sulfate-reducing clostridium bacteria. Therefore, the valuing of CLW efficiency in the laboratory showed that their valorization could be extended to the sludge stabilization field.

Coronavirus disease has become a worldwide threat affecting almost every country in the world. The aim of this study is to identify the COVID-19 cases (positive, recovery and death) in Algeria using the Double Exponential Smoothing Method and an Autoregressive Integrated Moving Average (ARIMA) model for forecasting the COVID-19 cases.The data for this study were obtained from March 21st, 2020 to November 26th, 2020. The daily Algerian COVID-19 confirmed cases were sourced from The Ministry of Health, Population and Hospital Reform of Algeria. Based on the results of PACF, ACF, and estimated parameters of the ARIMA model in the COVID-19 case in Algeria following the ARIMA model (0,1,1). Observed cases during the forecast period were accurately predicted and were placed within the prediction intervals generated by the fitted model. This study shows that ARIMA models with optimally selected covariates are useful tools for monitoring and predicting trends of COVID-19 cases in Algeria.

The aim of this paper is to evaluate the efficiency of the natural hydroxyapatite powder for anionic dye (Congo red) elimination from water and optimization of adsorption process parameters that are contact time (0-360 min), solution pH (4-9), initial dye concentration (400-2400 mg/l), and adsorbent dosage (0.4-20 g/l). Natural hydroxyapatite with high surface area was prepared from animal agriculture waste dromedary bone. X-ray diffraction, transmission electron microscopy, transform infrared spectroscopy, and elemental analysis characterizations of the powder prepared show a hexagonal structure, the irregular form of hydroxyapatite and presence of other elements as trace element. The results of adsorption tests demonstrated the high efficiency of natural hydroxyapatite for removal of Congo red from water solution whose maximum experimental capacity adsorption of Congo red by natural hydroxyapatite is 900 mg/g at pH 4.5, equilibrium time 240 min and adsorbent dosage 2 g/l. According to the correlation coefficient value, the pseudo-second order kinetic model identified the sorption mechanism of pollutant used on natural hydroxyapatite.The Freundlich isotherm is the best representative theoretical model of the dye molecules' adsorption on the natural hydroxyapatite support.