Table 1.

Different available technologies used to treat slaughterhouse wastewater.

Sl no.	Technology adopted	Input characteristics of slaughterhouse wastewater	Observations	References
(1)	Anaerobic treatment of slaughterhouse wastewaters in a UASB (Upflow Anaerobic Sludge Blanket) reactor and in an anaerobic filter (AF).	Slaughterhouse wastewater showed the highest organic content with an average COD of 8000 mg/L, of which 70% was proteins. The suspended solids content represented between 15 and 30% of the COD.	The UASB reactor was run at OLR (Organic Loading Rates) of 1–6.5 kg COD/m3/day. The COD removal was 90% for OLR up to 5 kg COD/m3/day and 60% for an OLR of 6.5 kg COD/m3/day. For similar organic loading rates, the AF showed lower removal efficiencies and lower percentages of methanization.	Ruiz et al. [9]
(2)	Anaerobic sequencing batch reactors.	Influent total chemical oxygen demand (TCOD) ranged from 6908 to 11 500 mg/L, of which approximately 50% were in the form of suspended solids (SS).	Total COD was reduced by 90% to 96% at organic loading rates (OLRs) ranging from 2.07 to 4.93 kg m−3 d−1 and a hydraulic retention time of 2 days. Soluble COD was reduced by over 95% in most samples.	Massé and Masse [10]
(3)	Moving bed sequencing batch reactor for piggery wastewater treatment.	COD, BOD, and suspended solids in the range of 4700–5900 mg/L, 1500–2300 mg/L, and 4000–8000 mg/L, respectively.	COD and BOD removal efficiency was greater than 80% and 90%, respectively at high organic loads of 1.18–2.36 kg COD/m3·d. The moving-bed SBR gave TKN removal efficiency of 86–93%.	Sombatsompop et al. [11]
(4)	Fixed bed sequencing batch reactor (FBSBR).	The wastewater has COD loadings in the range of 0.5–1.5 Kg COD/m3 per day.	COD, TN, and phosphorus removal efficiencies were at range of 90–96%, 60–88%, and 76–90%, respectively.	Rahimi et al. [12]
(5)	Chemical coagulation and electrocoagulation techniques.	COD and BOD5 of raw wastewater in the range of 5817 ± 473 and 2543 ± 362 mg/L.	Removal of COD and BOD5 more than 99% was obtained by adding 100 mg/L PACl and applied voltage 40 V.	Bazrafshan et al. [13]
(6)	Hybrid upflow anaerobic sludge blanket (HUASB) reactor for treating poultry slaughterhouse wastewater.	Slaughterhouse wastewater showed total COD 3000–4800 mg/L, soluble COD 1030–3000 mg/L, BOD5 750–1890 mg/L, suspended solids 300–950 mg/L, alkalinity (as CaCO3) 600–1340 mg/L, VFA (as acetate) 250–540 mg/L, and pH 7–7.6.	The HUSB reactor was run at OLD of 19 kg COD/m3/day and achieved TCOD and SCOD removal efficiencies of 70–86% and 80–92%, respectively. The biogas was varied between 1.1 and 5.2 m3/m3 d with the maximum methane content of 72%.	Rajakumar et al. [14]
(7)	Anaerobic hybrid reactor was packed with light weight floating media.	COD, BOD and Suspended Solids in the range of 22000–27500 mg/L, 10800–14600 mg/L, and 1280–1500 mg/L, respectively.	COD and BOD reduction was found in the range of 86.0–93.58% and 88.9–95.71%, respectively.	Sunder and Satyanarayan [15]