Polyhydroxyalkanoates (PHA) biosynthesis from kraft mill wastewaters: biomass origin and C:N relationship influence

The goal of this study is to evaluate the feasibility of PHA biosynthesis from kraft mill effluent using the batch system evaluating the biomass origin and C:N relationship influence. To evaluate feasibility, batch assays were carried out. Also, two levels of the BOD5:N:P relationship (100:5:1 and 100:1:0.2) and three different sludge origins were considered. Inocula were obtained from activated sludge treatment plants for a) sewage (SAS), b) paper mill (PAS) and c) kraft (KAS). The results show that the maximum Biological Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) removal was 80.5% and 59.7% respectively using KAS as inoculum. In these assays, kinetics constants were 17.9±3.2 mg L−1 and 46.5±1.2 d−1 for (KCOD) and (rmax), respectively under a BOD5:N:P relationship of 100:5:1. The maximum PHA accumulation was obtained under a BOD5:N:P relationship of 100:1:0.2 on the third day of batch assays using PAS sludge with 25.72% of the cells accumulating PHA and on the fifth day in batch using SAS and KAS sludge with 25.85% and 30.40% of cells accumulating PHA, respectively. Yields obtained for the 100:1:0.2 relationships ranged from 0.10–0.14 mg PHA mg−1 COD.

Responses in a Fathead Minnow (Pimephales promelas) Lifecycle Test and in Wild White Sucker (Catostomus commersoni) Exposed to a Canadian Bleached Kraft Mill Effluent

To evaluate currently available bioassays for their use in investigating the causes of pulp and paper mill effluent effects on fish reproduction, the responses of wild white sucker (Catostomus commersoni) collected from the receiving environment at the bleached kraft mill at La Tuque, Quebec, were compared with responses of fathead minnow (Pimephales promelas) exposed to effluent in a laboratory lifecycle test. White sucker collected at effluent exposed sites had increased liver size but none of the reproductive effects that had been documented in earlier field studies at this site. Exposure to 1, 3, 10, 30, and 100% bleached kraft mill effluent (BKME) in the lab led to significantly decreased length, but increased weight and liver size in male fathead minnow. Female length was also decreased and liver size was increased at high effluent exposures. Most effluent concentrations (1 to 30%) significantly increased egg production compared with controls. The fathead minnow lifecycle assay mirrored the effects seen in wild fish captured downstream of the BKME discharge. These results will be used to select short-term fish tests for investigating the causes of and solutions to the effects of mill effluents on fish reproduction.