Effectiveness of biopolymer coagulants in agricultural wastewater treatment at two contrasting levels of pollution

Abstract

Agricultural diffuse pollution is a major environmental problem causing eutrophication of water bodies. Despite the problem is widely acknowledged, there has been relatively few major advances in mitigating the problem. We studied the effectiveness of biopolymer-based (tannin, starch, chitosan) natural coagulants/flocculants in treatment of two different agricultural wastewaters that differed in their level of phosphorus pollution and turbidity. We used jar-tests to test the effectiveness of the biopolymer coagulants in reducing water turbidity, total phosphorus, and total organic carbon (TOC) from the wastewaters. In more polluted water (total phosphorus: 300 µg/L, turbidity: 130 FNU, TOC: 30 mg/L), all tested biopolymers performed well. The best reductions for different biopolymer coagulants were 64-95%, 80-98% and 14-27%, for total phosphorus, turbidity and TOC, respectively. Tannin and chitosan coagulants performed the best at doses of 5-10 mL/L, whereas starch coagulants had the best performance at 1-2 mL/L doses. Tannin and chitosan coagulants performed clearly better than the starch coagulants. In less polluted water (total phosphorus: 74 µg/L, turbidity: 3.9 FNU, TOC: 21 mg/L), chitosan and starch coagulants did not produce flocs at any of the tested doses. Tannin coagulant performed the best at doses of 5-8 mL/L, where reductions were 70%, 82%, and 22%, for total phosphorus, turbidity and TOC, respectively. The great reductions of phosphorus and turbidity suggests that biopolymer coagulants could be applied in treatment of agricultural water pollution. The high phosphorus retention in the biodegradable biopolymer sludge suggests that the sludge can be readily used as a phosphorus fertilizer, which would aid the recycling of nutrients.

Removal and recovery of nutrients and value-added products from wastewater: technological options and practical perspective

“…According to a recent study, wastewater containing high organic content prefers PHA biosynthesis and resource Tannin based coagulant at doses of 5-8 mL/L reduced the total phosphorus (70%), turbidity (82%) and TOC (22%) content [153] PLA or PEG Used in bone and dental implants, food packaging with low stiffness or high flexibility [154] PLA or potato pulp Food packaging with low stiffness, ductility, processability [155] Edible and biodegradable natural polymeric materials Used for preparing edible films and coatings, packaging materials, carriers of antimicrobial and anti-oxidative materials [156] Nanocomposite based biopolymers Used for the detection of pathogens, packaging, antimicrobial packaging, and the formation of barriers. It has also shown to improve food packaging [156,157] 1.0% chitosan Used for base coating and maintaining the safety and quality of fresh bell peppers, stored at room temperature for 21 days [158] Dextran-based hydrogels Physical strength: maximum strain (90%) and corresponding stress of 2.7 MPa.…”

Chemical waste and allied products

“…Turunen, Karppinen, and Ihme (2019) studied the efficacy of tannin, starch, and chitosan for two types of agricultural wastewater treatment. These two wastewaters differ in turbidity levels and pollution level by phosphorus.…”

The dietary supplement chitosan lowers serum phosphorus in a hemodialysis patient not tolerating prescription medications

“…Chitosan, a deacetylated glucosamine derived from chitin, is a nontoxic biodegradable and abundantly available biopolymer that binds anionic compounds. Its numerous industrial applications include phosphorus removal from agricultural wastewater 1 . Chitosan is also widely available as a dietary supplement for weight loss, by interfering in the absorption of lipids and bile acids 2 .…”